JPH0448808B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method for controlling the degree of polymerization of aromatic polyamide. More specifically, when producing an aromatic polyamide by reacting an aromatic dicarboxylic acid chloride and an aromatic diamine in an aprotic amide solvent, the dicarboxylic acid chloride is added stepwise to polymerize, and the viscosity of the polymer solution is adjusted. This invention relates to a method for controlling the degree of polymerization. Prior Art Aromatic polyamides obtained from aromatic diamines and aromatic dicarboxylic acids have high melting temperatures, high thermal decomposition temperatures, and high glass transition temperatures, and have excellent heat resistance and
It is known to provide molded products with excellent chemical resistance and other chemical and physical properties. and,
Aromatic polyamide fibers with excellent thermal properties are useful as heat-resistant, flame-retardant, and flame-retardant fibers for protective clothing, filter bags, and the like. In addition, fibers made of aromatic polyamide and having excellent mechanical properties such as large initial Young's modulus and strength are used as rubber reinforcement materials for tire cords, belts, hoses, etc., plastic reinforcement materials for composite materials, ropes, bulletproof clothing, etc. useful in the field. When molding aromatic polyamide into molded products such as fibers or films, it is important to keep the degree of polymerization within a small fluctuation range at the desired value.
This is extremely important for improving product performance and process stability. Therefore, it is required to control the degree of polymerization of the polymer even in the aromatic polyamide polymerization process. Solution polymerization or interfacial polymerization using aromatic diamine and aromatic dicarboxylic acid chloride is known as an industrial method for obtaining aromatic polyamide, but the polymerization reaction between aromatic diamine and polymerized dicarboxylic acid chloride Since this is a nonequilibrium and irreversible reaction, it is not possible to control the degree of polymerization by manipulating temperature and pressure, as in the melt polymerization of polyester and nylon, which is a reversible and equilibrium reaction. In other words, the degree of polymerization of aromatic polyamide is almost uniquely determined by the molar ratio of aromatic diamine and aromatic dicarboxylic acid chloride involved in the reaction, which is actually the molar ratio calculated by dividing the charged weight by the molecular weight. determined. Therefore, in order to keep the degree of polymerization within a small fluctuation range with good reproducibility, it is necessary to keep the reaction conditions such as temperature and time constant, and to
It is extremely important to accurately measure the amount of monomer charged. However, in actual polymerization reactions, even if the measurement accuracy is improved, the variation in the degree of polymerization cannot be reduced to a satisfactory level. First, there is a limit to the accuracy of industrial measurement of raw materials, whether it is volumetric or gravimetric measurement.Second, in actual polymerization reactions, side reactions with solvents and water, impurities in raw materials, etc. This is because the reaction with the polymer affects the degree of polymerization in a complex manner. Purpose of the Invention The purpose of the present invention is to provide a system with high precision that can overcome the effects of limitations in the measurement accuracy of raw materials, fluctuations in the amount of impurities in solvents and monomers, and fluctuations in reaction conditions such as temperature and time. An object of the present invention is to provide a method for controlling the degree of polymerization. Composition of the Invention The method of the present invention to achieve the above object is to produce an aromatic polyamide by reacting an aromatic dicarboxylic acid chloride and an aromatic diamine in an aprotic amide solvent, and the method involves reducing the number of moles of the dicarboxylic acid to a , where b is the number of moles of diamine, a/b=m
When dicarboxylic acid chloride and diamine are reacted under the conditions of 0.9 < m < 1, dicarboxylic acid chloride is dissolved in the same solvent used for the polymerization in the polymerization solution at 0°C or below. , is a polymerization degree control method characterized by adding dicarboxylic acid chloride stepwise to polymerize it and adjusting the viscosity of the polymerization solution. The method of the invention is applied to solution polymerization using aromatic dicarboxylic acid chlorides and aromatic diamines. Aromatic dicarboxylic acid chlorides include asophthalic acid chloride, terephthalic acid chloride,
2,6-naphthalene dicarboxylic acid chloride,
Examples include 1,4-naphthalene dicarboxylic acid chloride. Further, aromatic diamines include metaphenylene diamine, paraphenylene diamine, 4,4'-diaminodiphenyl, 2,6-diaminonaphthalene, 1,4-diaminonaphthalene, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone,
Examples include 4,4'-diaminodiphenylmethane. In addition, the method of the present invention can be used not only when producing an aromatic polyamide homopolymer using one type of aromatic dicarboxylic acid chloride and one type of aromatic diamine, but also when using one or more types of aromatic dicarboxylic acid chloride or/and It also applies to the production of aromatic polyamide copolymers using one or more aromatic diamines. Furthermore, 20 mol % or less of aliphatic diamine and/or aliphatic dicarboxylic acid chloride may be used based on the total monomers used. Furthermore, monoamines and/or monocarboxylic acid chlorides may be used to adjust the degree of unterminated polymerization. The solvent used in the solution polymerization in the present invention must be a solvent that can dissolve the aromatic dicarboxylic acid, aromatic diamine, and polymer produced by the polymerization reaction, and such a solvent must be an aprotic one. A neutral amide solvent is used. Typical examples include dimethylformamide (DMF), dimethylacetamide (DMAC), N
-Methyl-2-pyrrolidone (NMP), tetramethylurea (TMU), and hexamethylphosphoric triamide (HMPA). Among these solvents, from the viewpoint of chemical stability and ability to dissolve aromatic polyamides, solvents are more preferable.
DMAC, NMP, and TMU, with NMP being the most preferred. In the method of the present invention, it is first necessary to carry out the polymerization under the conditions of 0.9<m<1, where a/b=m, where the number of moles of dicarboxylic acid chloride is a and the number of moles of diamine is b. If m>1, the majority of the terminal groups in the resulting polymer will be chloroformyl groups, which is not suitable for the method of controlling the degree of polymerization of the present invention.
On the other hand, if m is too small, various problems will occur. First, if m is small, oligomers or polymers with a low degree of polymerization will be produced by polymerization, and since these generally have poor dissolution stability and are likely to precipitate, a uniform solution may not be obtained. Furthermore, when m is small, the viscosity of the polymerization solution is also small, and this is not suitable for the method of the present invention, which involves controlling the degree of polymerization by adjusting the viscosity of the polymerization solution. Therefore, m should be in the range 0.9<m<1, with 0.95<m<1 being generally preferred. The most preferred range is 0.99<m<1. In the method of the present invention, in order to polymerize the dicarboxylic acid chloride and the diamine under the condition of 0.9<m<1, the diamine solution and the dicarboxylic acid chloride may be mixed. As for the dicarboxylic acid chloride, the mixing method may be a batch method or a continuous method. According to the method of the present invention, dicarboxylic acid chloride is newly added to and mixed with the thus obtained polymer solution. Since most of the terminal groups of the polymer in the previously obtained polymer solution are amino groups, the polymer reacts with the newly added dicarboxylic acid chloride to further increase the degree of polymerization. In this case, the dicarboxylic acid chloride used for addition is added to the same solvent used for the polymerization reaction at 0°C.
It can be used in the form of a solution which is dissolved below. Adding dicarboxylic acid chloride in the form of a solution makes it easier to measure the volume by increasing the measuring volume, and it also becomes possible to measure automatically using a pump, etc.
Furthermore, it becomes easy to mix with a high viscosity solution that has been polymerized in advance. In this case, the solvent for dissolving the dicarboxylic acid chloride must be an inert solvent that does not react with the dicarboxylic acid chloride. Examples of such solvents include hydrocarbons such as benzene and hexane, hydrogen halides such as methylene chloride and chloroform, and tetrahydrofuran, but these do not dissolve aromatic polyamides and tend to cause gelation. Since it has a boiling point, it tends to cause foaming phenomenon when molding fibers, films, etc., and is not preferable except when manufacturing foam molded products. Therefore, the solvent in which the dicarboxylic acid chloride is dissolved needs to be the same as the polymerization solvent. However, the solvent used for solution polymerization of aromatic polyamides is an aprotic amide solvent, and it is known that they easily react with dicarboxylic acid chlorides. The use of dissolved solutions for polymerization has not been done. Furthermore, since dicarboxylic acid chloride is extremely reactive with water and the like, and its activity for polymerization reaction is reduced, it is also necessary to keep the amount of water and impurities in the aprotic amide solvent to an extremely small amount. As a result of intensive research into this problem, the inventors of the present invention surprisingly found that they were able to purify the aprotic amide solvent, reduce the moisture content, and maintain the solution in which dicarboxylic acid chloride was dissolved at low temperature. For example, we have discovered that dicarboxylic acid chloride is extremely stable and maintains a constant polymerization reaction activity for a long time. That is, the various difficulties mentioned above can be easily overcome by polymerizing the dicarboxylic acid chloride dissolved in the same solvent used in the polymerization at 0°C or lower as a solution. The degree of polymerization can be easily controlled by adjusting the viscosity of the polymerization solution. In the method of the present invention, when dicarboxylic acid chloride is dissolved in an aprotic amide solvent, the solvent must be kept at a low temperature beforehand, and it is necessary to maintain the temperature at a low temperature not only during dissolution but also after dissolution. There is. When the temperature of the solvent is high, a reaction occurs between the dicarboxylic acid and the solvent, and the polymerization reaction activity of the dicarboxylic acid decreases significantly, and the polymerization reaction ability changes over time, making it difficult to use in the method of the present invention. becomes. The temperature is preferably 0°C or lower, preferably -10°C or lower, and more preferably -15°C or lower, as long as it is at least the temperature at which the solvent solidifies. Depending on the concentration of dicarboxylic acid chloride, a slurry with some of the dicarboxylic acid chloride undissolved may be formed at low temperatures, but if the slurry is uniformly dispersed and no concentration unevenness occurs during volumetric measurement, it can be used in such a slurry form. It's okay. Although the concentration of the dicarboxylic acid chloride solution can be selected appropriately, it is preferably in the range of 1 to 20% by weight. In addition, since the polymer concentration in the final polymerization solution varies depending on the amount of dicarboxylic acid chloride solution added, it is preferable that the ratio of the amount of dicarboxylic acid solution added to the entire polymerization solution is small; It is preferably 1 or less, more preferably 1/500 or less, and most preferably 1/1000 or less. In the method of the present invention, dicarboxylic acid chloride and diamine are polymerized in advance under the conditions of 0.9 < m < 1, and then dicarboxylic acid chloride is added stepwise to the polymerization solution and polymerized to adjust the viscosity of the polymerization solution. The degree of polymerization is controlled by The viscosity of a polymer solution is uniquely determined by the degree of polymerization of the polymer if the solvent, the type of polymer, the concentration of the polymer, and the temperature of the solution are constant. Therefore, by keeping conditions such as the solvent, type of polymer, concentration of the polymer, and temperature of the solution constant, the relationship between the viscosity of the solution and the degree of polymerization of the polymer is determined in advance to correspond to the desired degree of polymerization. The degree of polymerization can be controlled by adding dicarboxylic acid chloride stepwise and polymerizing until the solution viscosity is reached. The necessary addition amount and addition rate of the dicarboxylic acid chloride to be added stepwise can be easily determined empirically or semi-theoretically while measuring the increase in viscosity of the polymerization solution. The viscosity of the polymerization solution can be measured by installing a general-purpose viscometer in the polymerization apparatus, but from an industrial perspective, it is better to measure the stirring power by using the correspondence between the viscosity of the polymerization solution and the stirring power. good. Since the degree of polymerization corresponds to the viscosity of the solution, and the viscosity of the solution corresponds to the stirring power, it can be understood that the degree of polymerization corresponds to the stirring power. The stirring power varies not only by the viscosity of the solution, but also by the shape of the polymerization stirring device, the number of rotations, the amount of polymerization solution, etc. Therefore, under certain conditions, the relationship between the stirring power, the solution viscosity, and the degree of polymerization is determined. It is sufficient to find the relationship in advance. Effects of the Invention According to the method of the present invention as described above, the degree of polymerization can be controlled to a predetermined degree even if there are variations in the measurement accuracy of raw materials, the amount of impurities in the solvent or monomer, or the reaction conditions in the polymerization process. can do. Therefore, it is possible to produce an aromatic polyamide polymer with extremely little variation in the degree of polymerization, and in turn, it is possible to obtain molded products such as high-quality fibers and films. Examples Examples and comparative examples of the method of the present invention will be described in detail below. In the examples, the intrinsic viscosity (IV) of the polymer is used as an index of the degree of polymerization. Intrinsic viscosity (IV) is a value measured at 30°C for a solution with a polymer concentration of 0.5 g/dl in 98% concentrated sulfuric acid. Comparative Example 1 N-methyl-2- with a moisture content of about 30 ppm was placed in a mixing tank with an anchor-shaped stirring blade in which nitrogen was flowing.
After adding 205 pyrrolidone (NMP), 2764 g of paraphenylenediamine (PPD) from Company A and 2764 g of paraphenylenediamine (PPD) from Company A and B
3,4'-diaminodiphenyl ether (3,
4′-DAPE) were accurately weighed and added to dissolve. Into this diamine solution, at a temperature of 30°C and a stirring speed of 64 times/min, 8 to 32 meshes of terephthalic acid chloride (TPC) powder from Company C was added.
10320g (m=0.9947) was accurately weighed and added.
After the temperature of the solution rises to 53℃ due to the heat of reaction
It was heated to 85°C for 60 minutes. During this time, the viscosity of the solution continued to increase. Stirring was continued for another 15 minutes at 85°C, and after confirming that the viscosity increase of the solution had ended, sampling was performed to measure the IV of the obtained copolymer. When polymerization was repeated five times using the same procedure as described above, the IV values were 3.31, 3.38, 3.28, 3.43, and 3.35, with large variations. Next, PPD from Company D was used in place of Company A, and the polymerization was repeated five times under the same operating conditions.
The IVs at that time were 2.90, 2.78, 2.80, 2.95, and 2.88, and there was a large variation, causing a difference in the average value from that of Company A. Example 1 Polymerization was carried out using the same equipment and raw materials as in Comparative Example 1. A after adding NMP205 with a moisture content of about 30 ppm
2,764 g of PPD from Company B and 5,114 g of 3,4'-DAPE from Company B were accurately weighed and dissolved. While the temperature of this diamine solution was 30° C. and the stirring rotation speed was 64 times/min, 8 to 32 meshes of 10,300 g of TPC manufactured by Company C (m=0.9928) were accurately weighed and added. The temperature of this solution is due to the heat of reaction.
After rising to 53℃, heat for 60 minutes to 85℃,
Keep at 85°C for minutes. During this 75 minutes, TPC
A solution dissolved in NMP was added little by little, and the polymerization was completed at a temperature of 85° C., a stirring rotation speed of 64 times/min, and a stirring power of 3.50. TPC solution storage period when such operation is repeated 5 times,
The number of additions, amount of solution added, final power, and IV are summarized in Table 1. In addition, the TPC solution has a moisture content of approximately 30 ppm.
NMP2 was cooled to minus 15°C, and 300g of TPC was added to it in nitrogen and dissolved. This solution was stored at minus 15° C. under nitrogen, and the same solution was added by measuring the volume using a plunger pump in each of the five polymerizations.

[Table] As is clear from Table 1, the polymerizability of the TPC NMP solution was maintained stably for 47 hours. Example 2 Polymerization was carried out in the same manner as in Example 1 except that the temperature of the TPC NMP solution was changed from -15°C to -5°C. The results are summarized in Table 2.

[Table] As is clear from Table 4, as the storage temperature becomes higher and the storage time becomes longer, the total amount of TPC solution added to obtain the same IV increases. Comparative Example 2 Polymerization was carried out in the same manner as in Example 1, except that the temperature of the TPC NMP solution was changed from -15°C to +10°C. The results are shown in Table 3.

[Table] Table 3 shows that when the storage temperature becomes significantly higher, the total amount of added solution increases, and when the storage time becomes longer, even if more than a certain amount of TPC solution is added, the IV does not increase. It can be seen that the polymerization activity was significantly reduced and it became unusable.

Claims (1)

[Claims] 1. In producing an aromatic polyamide by reacting an aromatic dicarboxylic acid chloride and an aromatic diamine in an aprotic amide solvent, the number of moles of the dicarboxylic acid chloride is a, and the number of moles of the diamine is When b is a/b=m, 0.9<m<1
After reacting the dicarboxylic acid chloride and the diamine under the following conditions, add 0% of the dicarboxylic acid chloride to the polymerization solution in the same solvent used for the polymerization.
1. A method for controlling the degree of polymerization, which comprises stepwise adding dicarboxylic acid chloride to a solution dissolved and maintained at a temperature below 0.degree. C. to polymerize and adjust the viscosity of the polymerization solution. 2. The method for controlling the degree of polymerization according to claim 1, wherein the dicarboxylic acid chloride is added stepwise as a solution dissolved and maintained at -10°C or lower.