JPH0132822B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing aminoschiff base (hereinafter abbreviated as ASB). ASB
is known to be easily converted into α,ω-diaminoketones (salts) by acid hydrolysis, and can further be converted into compounds useful as polymer raw materials such as α,ω-diaminoalkanes. be. It is well known that when lactams, lactam oligomers, their ring-opened polymers, or their ring-opened monomers, ω-aminoalkane carboxylic acids, are heated and carbonized in the presence of a strong base compound, the corresponding ASB is produced. Various methods have been proposed using alkaline earth metal oxides and hydroxides as strong base compounds (for example,
Publication No. 16015, Special Publication No. 1972-26661, Special Publication No. 1973
-26662, JP-A-137974, French Patent No. 225290). However, with these known techniques, the yield of ASB (ASB produced relative to the charged lactams) is
It is well known to those skilled in the art that the ratio (% of On the other hand, a method has been proposed in which an alkali metal hydroxide is used as the strong base compound, treated under reflux at 100 to 200°C, and then carbonized (Japanese Patent Publication No. 7432/1982). However, this method requires the alkali metal hydroxide to be used in an amount equal to or more than the equivalent mole of the lactam, and even then, it was difficult to complete the reaction. Furthermore, when using an alkali metal hydroxide in a molar amount or less, the reaction rate is low and a large amount of unreacted lactams remains. In order to improve this point, ε-caprolactam was used as a raw material and 7-(5'-aminopentyl)-
When obtaining 3,4,5,6-tetrahydro-2H-azepine, a method has been proposed in which at least an equimolar amount of lithium hydroxide is used per carbonyl group in the raw material caprolactam (Japanese Patent Application Laid-Open No.
54-125654). Although this proposed method still uses more than the equivalent mole of lithium hydroxide, it provides an ASB yield and selectivity of around 90%, and the lithium carbonate by-produced during the reaction is different from the calcium carbonate produced in the conventional system. Because it has slurry and powder properties that are easier to stir than other materials, it is also excellent in reducing problems caused by inability to stir during the reaction. However, this method requires a large amount of lithium hydroxide, which is an expensive chemical, in an amount of at least the equivalent mole per carbonyl group in the caprolactam raw material, so it is rarely implemented industrially from an economical point of view. It was impossible. If the amount of lithium hydroxide used is less than the equimolar amount, since the reaction is a stoichiometric reaction as shown in the chemical formula below, the conversion rate of lactam will immediately decrease and the yield of ASB will decrease. Not only that, but also the ASB selectivity decreased significantly. In other words, in the conventionally known method, in order to produce ASB with good yield and selectivity, it is essential that the amount of lithium hydroxide used be at least an equimolar amount (stoichiometric amount or more). Therefore, it was impossible to actually use it industrially. The present inventors recognized this current situation and achieved high yield.
As a result of intensive research into the development of a process that provides ASB and can be carried out economically, we have developed a method in which a very small amount of lithium hydroxide is used as a so-called catalyst as a strongly basic decarboxylation dimerization agent in such a reaction. fully economical and with high yield.
The present invention was achieved by discovering that ASB can be obtained. That is, the present invention uses a raw material selected from a 5- to 7-membered ring lactam, a lactam oligomer, a ring-opening polymer thereof, or a ring-opening monomer thereof, ω-aminoalkanecarboxylic acid, per equivalent of carbonyl group in the raw material. 200 to 550°C in the presence of 0.003 equivalent or more and 0.2 equivalent of lithium hydroxide and 0.7 equivalent or more of calcium hydroxide and/or calcium oxide
This is a method for producing an aminoschiff base represented by the following general formula (), which is characterized by heating and carbonizing at a temperature range of . (In the formula, n represents an integer of 4 to 6.) The amino Schiff base obtained in the present invention refers to an amino Schiff base represented by the following general formula (). By ring-opening hydration of this amino Schiff base, an α,ω-diaminoketone represented by the following general formula () can be obtained. (wherein n is an integer from 4 to 6) According to the present invention, the amount of catalyst per carbonyl group in the lactams is 20% or less, usually only a few percent, of the equivalent amount (i.e., at least the amount conventionally required). By simply heating and carbonizing lactams using a small amount (trace amount) of lithium hydroxide, ASB yield and ASB selectivity equivalent to those obtained when using an equivalent or more amount of lithium hydroxide per carbonyl group in the lactams can be obtained. is possible. In this way, the amount of expensive lithium hydroxide used per unit of ASB produced can be dramatically reduced, and the yield and selectivity of ASB can still be maintained at a high level, making it possible to implement this method industrially for the first time. It became. In other words, the first advantage of the present invention is that expensive lithium hydroxide can be used in only a small catalytic amount;
The same high level as when only the required amount was used in the past.
ASB yield and selectivity can be obtained. This made it possible to implement this method industrially for the first time. Calcium hydroxide and/or calcium oxide used in combination with lithium hydroxide in an amount of 0.7 or more equivalents per carbonyl group in the lactams are inexpensive and do not present any disadvantage in the industrial implementation of this method. A second advantage of the present invention is that by using only a small amount of expensive lithium hydroxide, it is possible to obtain reaction operability similar to that obtained by using only the amount conventionally required. In other words, when ASB, which is normally produced by dry heating raw material lactams in the presence of calcium hydroxide or calcium oxide, is collected by distillation, calcium carbonate is produced and precipitated as the reaction progresses, so the reaction is not liquid-solid. It is known to those skilled in the art that the reaction proceeds in a homogeneous system, making it difficult to heat uniformly, and furthermore, in the final stage of the reaction, the by-product carbonate turns into lumps, making it impossible to stir the contents of the reactor in many cases. is well known. On the other hand, as shown in Japanese Patent Application Laid-Open No. 125654/1983, such stirring troubles can be significantly reduced if lithium hydroxide is used in an amount equal to or more than the equivalent amount per carbonyl group in the raw material lactam. In contrast, in the method of the present invention, lithium hydroxide is used in an amount of 20% or less, usually only a few percent, per carbonyl group in the raw material lactams, and calcium hydroxide and/or calcium oxide are used in combination, and more than an equivalent amount of hydroxide is used. It is possible to reduce the above-mentioned stirring troubles in almost the same way as when using lithium. A third advantage of the present invention is improved decarboxylation dimerization rate. As mentioned above, by using a catalytic amount of lithium hydroxide in combination with calcium hydroxide and/or calcium oxide, the reaction rate of this reaction becomes clearly higher than when lithium hydroxide is not used. The industrial advantages of this are important, such as improved productivity and reduced capital investment. Based on the above-mentioned content, the inventors have determined that, for example, the following formula
It is inferred that reactions like (1) and (2) proceed during the decarboxylation dimerization reaction of lactams. In other words, lithium hydroxide acts catalytically within the system and decarboxylates and dimerizes lactams while going back and forth with lithium carbonate. Therefore, it is believed that only a few percent of the carbonyl groups in the lactams is sufficient for lithium hydroxide to exhibit the above-mentioned remarkable effects. (2) Li ₂ CO ₃ +Ca(OH) ₂ →2LiOH+CaCO _3In the end, The so-called double decomposition reaction, in which 1 equivalent of lithium carbonate and 1.05 equivalents of calcium hydroxide are heated in a slurry state with stirring in the presence of a large amount of water to produce lithium hydroxide and calcium carbonate, is for example RL.
It is known from NIELSEN et al., I〓EC, 43 (12), 2636 (1951), and the present inventors also mixed 39 g of lithium carbonate and 39 g of lithium hydroxide (molar ratio 1:1.2) with 150 ml of water.
It was confirmed that lithium hydroxide could be obtained in high yield by heating under reflux for 16 hours. However, such a metathesis reaction is completely different from the conventionally known reaction system, that is, it is a substantially anhydrous system such as the decarboxylation dimerization reaction system of lactams, and is conducted in the presence of a large amount of organic compounds. It is surprising that it appears that the object of the present invention is achieved in a sufficiently short period of time. An even more surprising new discovery is that lithium hydroxide, which is present in a very small amount, preferentially reacts with lactams compared to calcium hydroxide, which is present in an equivalent amount several tens of times or more, or lithium hydroxide, which is present in a very small amount, compared to the above-mentioned reaction (1).
This is a fact that is thought to proceed first compared to the reaction between lactams and calcium compounds. That is, the remarkable effect of the present invention already mentioned is that: A. Lithium hydroxide, which is present in very small amounts, reacts with lactams preferentially over calcium hydroxide and calcium oxide, which are present in large quantities, to form ASB and lithium carbonate (i.e. , reaction (1) occurs first), B The lithium carbonate thus produced is simultaneously converted into calcium hydroxide or oxidized lactams under suitable reaction conditions to decarboxylate and dimerize lactams to obtain ASB. It can be understood that this phenomenon was developed based on two novel facts: lithium hydroxide reacts with calcium and returns to its original form (that is, reaction (2) continues to occur). It is thought that lithium hydroxide acts as a catalyst in this reaction system by simultaneously realizing A and B. Note that if potassium hydroxide or sodium hydroxide, which are also alkali metal hydroxides, are used instead of lithium hydroxide in the present invention, not only will the effects of the present invention not be exhibited at all, but the ASB yield and selection will be adversely affected. rate worsens. This is as shown later in the comparative example. Hereinafter, the contents of the present invention will be explained in detail. The starting materials used in the present invention are 5- to 7-membered lactams, lactam oligomers, polyamides that are ring-opened polymers thereof, or ω-
Any aminoalkane carboxylic acid may be used. Specific examples include α-pyrrolidone, α-piperidone, and ε-caprolactam; oligomers thereof; nylon 4, nylon 5, and nylon 6; γ-aminobutyric acid, δ-aminovaleric acid, and ε-aminocaproic acid. Furthermore, the raw material lactams used in the present invention do not necessarily have to be of high quality, such as lactams recovered during polyamide production, depolymerized lactams,
Oligomers or polymer scraps are also sufficient. Thus, the present invention is a method for obtaining ASB by dry heating such lactams in the presence of a decarboxylating dimerizing agent, and is characterized by the use of a trace amount of lithium hydroxide, called a catalytic amount, as the dimerizing agent. The amount of lithium hydroxide used is 0.003 equivalent or more and 0.2 equivalent or less relative to the carbonyl group of the raw material lactam.
This is because if the amount is less than 0.003 equivalent, the effect of adding lithium hydroxide will not be sufficient, and if the amount is increased by 0.2 equivalent or more, the effect of adding lithium hydroxide will not be particularly improved. Usually the preferred usage amount is 0.005 equivalent or more
It is 0.1 equivalent or less. The supply form of lithium hydroxide may be anhydrous lithium hydroxide, lithium hydroxide monohydrate, or even an aqueous solution of lithium hydroxide. Usually, monohydrate salt, which is industrially easily available, is used. The invention further uses calcium hydroxide or/and calcium oxide together with lithium hydroxide. The amount used is 0.7 equivalent or more based on the carbonyl group of the raw material lactam. If it is less than this, a sufficient conversion rate of lactams cannot be obtained, and therefore the yield and selectivity of ASB will be low. The more the amount is 0.7 equivalents, the better, and there is no need to specifically limit the amount, but 2 equivalents or less is sufficient mainly from an economical point of view. The normally preferred amount used is in the range of 0.8 equivalents to 1.6 equivalents. The reaction according to the present invention is achieved by heating and carbonizing a mixture of lactams, lithium hydroxide and calcium hydroxide or/and calcium oxide at a temperature range of 200 to 500°C to distill off the reactant ASB. Ru. The reaction temperature varies depending on the lactam, but below 200°C there is virtually no distillation of the product, while above 550°C there is no distillation of the target product.
This generally results in a decrease in the yield of ASB. This reaction can be carried out by any of the batch method, semi-batch method and continuous method. In other words, the batch method involves mixing lactams and the above dimerizing agent and charging the mixture into a reactor and raising the temperature to a predetermined temperature while stirring.The lactam and dimerizing agent are continuously supplied to the reactor, and the produced ASB is continuously produced. It is possible to carry out either a semi-batch method in which the by-product carbonate is not continuously discharged out of the reaction system, or a continuous method in which the supply of these raw materials and the withdrawal of the products and by-products are continuous. be. Furthermore, before supplying these raw materials to the reactor, they are mixed and preheated to a temperature below the decarboxylation dimerization reaction temperature to convert the raw lactams into calcium and lithium salts of ω-aminoalkane carboxylic acid, and then reacted. It is also a preferred embodiment to supply the liquid to a container. Thus, in the method of the present invention, as the reaction progresses,
ASB is distilled off, and in order to facilitate distillation, this reaction may be carried out under a stream of gas inert to the reaction, such as nitrogen or ammonia, or may be carried out under reduced pressure. Next, examples of the present invention will be shown. In the examples, the lactam reaction rate, ASB yield, and ASB selectivity are values calculated according to the following formula. Lactam reaction rate (%) = ([Supplied lactam (mol)] - [Recovered or by-produced lactam (mol)]) / Supplied lactam (mol) x 100 ASB selectivity (%) = Produced ASB (mol) )/([Supplied lactam (mol)] - [Recovered or by-produced lactam (mol)]) ×
2 x 100 ASB yield (%) = ASB produced (mol) / Lactam supplied (mol) x 2 x 100 Example 1 ε-caprolactam 1.0 mol, lithium hydroxide monohydrate 0.010 mol (carbonyl group of lactams) (hereinafter abbreviated as "C=0")) and 0.55 mol of calcium oxide (hereinafter abbreviated as "C=0")
(1.1 equivalents) was placed in a 500 ml four-necked stainless steel flask, and the temperature was raised to 250°C while stirring and flowing nitrogen at a rate of 20 ml/min. After distillation of water was completed, the temperature was raised to 340-350°C and the distillate was collected, and finally the nitrogen flow rate was increased to 100 ml/min to collect all the distillate. The reaction results were as shown in Example 1 in Table 1. The produced distillate was analyzed by gas chromatography (a 2.5 m glass column packed with 15% Apiezon Grease L and 4% KOH supported on Diasolid uH80-100 mesh was used. Column temperature was 200.
°C, and the internal standard was dodecamethylenediamine). Compared to Comparative Example 1 and Comparative Example 2 shown later, ASB
It is clear that the yield and selectivity are significantly improved. Example 2 Lithium hydroxide 1 used in the previous Example 1
The amount of water salt is 0.067 mol (for "C=0"
Exactly the same experiment was carried out except that the amount was changed to 0.067 equivalents). The reaction results are also shown in Table 1. The yield and selectivity of ASB are further improved compared to Example 1, and as is clear from comparison with Comparative Example 3 shown later, equimolar to lactam (i.e., to "C=0")
It is clear that this is equivalent to the case where lithium hydroxide monohydrate (1.0 equivalent) is used. Comparative Example 1 The same experiment as in Example 1 above was conducted except that lithium hydroxide monohydrate was not used. The reaction results are also shown in Table 1. ASB yield and selectivity are shown in Examples 1 and 2.
It is clearly inferior to the case of In this experiment, the required stirring power was significantly higher than in Examples 1 and 2, and it was necessary to turn the stirring rod by hand for a period of time during the reaction. Comparative Example 2 The same experiment as Comparative Example 1 was conducted except that the amount of calcium oxide was increased to 3.0 equivalents relative to "C=0". The results are also shown in Table 1. It is clear that there is no improvement compared to Comparative Example 1 even if a large amount of calcium oxide is used. Comparative Example 3 1.0 mol of ε-caprolactam and 1.02 mol of lithium hydroxide monohydrate (1.0 equivalent relative to "C=0") were charged and treated in the same manner as in Example 1. The reaction results are also shown in Table 1. Although the yield and selectivity of ASB are similar to those in Example 2, this method cannot be implemented industrially due to the large amount of expensive lithium hydroxide used. Comparative Example 4 The same experiment as in Comparative Example 3 above was conducted except that 0.5 mol (0.5 equivalent for "C=0") of lithium hydroxide monohydrate was used. The reaction results are also shown in Table 1, with a small amount of lithium hydroxide.
Even compared to Example 1 using 0.01 equivalent, ASB yield,
Both ASB selection rates are significantly inferior. Example 3 ε-caprolactam 1.0 mol, lithium hydroxide monohydrate 0.01 mol (0.01 for "C=0"
equivalent) and 0.55 mol of calcium hydroxide (“C
Example 1
processed in the same way. The reaction results are lactam reaction rate,
ASB yield and ASB selectivity each 88.3%,
They were 85.7% and 97.0%. Example 4 Lactam oligomer recovered at an ε-caprolactam synthesis factory (ε-caprolactam 39%,
Composition of 58% cyclic oligomers and 3% chain oligomers. ε
114 g (equivalent to 1 mole of ε-caprolactam), 0.60 mole of calcium hydroxide (for "C=0")
1.20 equivalent) and 0.05 mol of lithium hydroxide monohydrate (0.05 equivalent for "C=0"),
It was treated in the same manner as in Example 1. The reaction results are lactam reaction rate, ASB yield, and ASB selectivity, respectively.
They were 89.1%, 85.3% and 95.7%. Comparative Example 5 The same experiment as in Example 4 was conducted except that lithium hydroxide monohydrate was not used. The reaction results were lactam reaction rate, ASB yield, and ASB selectivity of 81.6%, 75.8%, and 92.9%, respectively. Example 5 α-pyrrolidone 0.176 mol, calcium hydroxide
0.106 mol (1.20 equivalents for "C=0") and 0.0035 mol of lithium hydroxide monohydrate ("C=0")
(0.02 equivalents) into a 100 ml three-necked glass flask, and heated to 250°C while stirring and flowing nitrogen at 20 ml/min. When the distillation of ASB is no longer observed, the temperature is raised to 270℃, and the nitrogen flow is 150ml/min.
and continue collecting distillate for an additional hour. The reaction results were as shown in Table 2. The produced distillate was analyzed using gas chromatography (15% PEG20M and 5% KOH were analyzed using simalite).
2.5 supported and filled on W402D80−100 mesh
A m glass column was used. The column temperature was 180°C, and the internal standard agent was cyclododecane. The yield and selectivity of ASB are significantly improved compared to Comparative Example 6 shown later. Comparative Example 6 The same experiment as in Example 5 was conducted except that lithium hydroxide monohydrate was not used. The reaction results are also shown in Table 2. It is clearly inferior to Example 5. Comparative example 7 α-pyrrolidone 0.176 mol, lithium hydroxide
Monohydrate 0.180 mol (1.02 equivalent for "C=0")
was charged and treated in the same manner as in Example 5. however,
In this case, it was necessary to raise the reaction temperature to 300°C in order to distill off all of the produced ASB. The reaction results are also shown in Table 2. Although the ASB yield and selectivity are almost the same as in Example 5, they are not suitable for industrial use in that they require a large amount of expensive lithium hydroxide and a higher reaction temperature. It is difficult to implement on a large scale. Comparative Example 8 In Example 3 above, potassium hydroxide was added in place of lithium hydroxide at a concentration of 0.20% for "C=0".
Exactly the same experiment as in Example 3 was conducted except that equivalent amounts were used. The reaction results are lactam reaction rate, ASB yield,
and ASB selection rates were 93.0%, 62.9%, and 67.6%, respectively. The results were also similar when sodium hydroxide was used instead of potassium hydroxide. The reaction results are not only significantly inferior to the results of Example 3 using lithium hydroxide, but also clearly inferior to the results of Comparative Example 5 using only calcium hydroxide. That is, potassium hydroxide and sodium hydroxide do not have a desirable catalytic effect like lithium hydroxide in the present invention, and on the contrary, it is considered that they exhibit a poor catalytic effect. Example 6 ε-caprolactam 1.0 mol, lithium hydroxide monohydrate 0.01 mol (0.01 mol for "C=O"
equivalent), 0.275 mol of calcium oxide (“C=O”
0.55 equivalents) and calcium hydroxide
0.275 mol (0.55 equivalent to "C=O") was charged and treated in the same manner as in Example 1. The reaction results were lactam reaction rate, ASB yield, and ASB selectivity of 89.5%, 82.8%, and 92.5%, respectively. Example 7 ε-aminocaproic acid 1.0 mol, lithium hydroxide monohydrate 0.01 mol (0.01 mol for "C=O"
equivalent), and 0.55 mol of calcium oxide (1.1 equivalent to "C=O") were charged, and the same treatment as in Example 1 was carried out. The reaction results were lactam reaction rate, ASB yield and ASB selectivity of 91.8% and 80.3%, respectively.
It was 87.5%. Example 8 Nylon 6 polymer (ηr=2.4) 113g (C=
1.0 mol as O), 0.01 lithium hydroxide monohydrate
mole (0.01 equivalent to "C=O"), calcium oxide 0.55 mole (1.1 equivalent to "C=O")
It was prepared and treated in the same manner as in Example 1. The reaction results were lactam reaction rate, ASB yield, and ASB selectivity of 93.8%, 70.8%, and 75.5%, respectively. Example 9 0.176 mol of γ-aminobutyric acid, lithium hydroxide
0.0035 mol of monohydrate (0.02 equivalent to "C=O"), 0.106 mol of calcium hydroxide ("C=O")
1.2 equivalents) and treated in the same manner as in Example 5. The reaction results were lactam reaction rate, ASB yield, and ASB selectivity of 83.0%, 45.1%, and 54.3%, respectively. Example 10 Nylon 4 polymer (ηr = 2.2) (0.176 mole as C=O), 0.0035 mole of lithium hydroxide monohydrate (0.02 equivalent to "C=O"), 0.10 mole of calcium hydroxide (0.10 mole as "C=O") = 1.2 equivalents for O”)
It was prepared and treated in the same manner as in Example 5. The reaction results were lactam reaction rate, ASB yield, and ASB selectivity of 85.1%, 40.3%, and 47.4%, respectively.

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【table】

Claims (1)

[Scope of Claims] 1. A raw material selected from a 5- to 7-membered ring lactam, a lactam oligomer, a ring-opening polymer thereof, or a ring-opening monomer thereof, ω-aminoalkane carboxylic acid, is per equivalent
The following general formula (characterized by heating and carbonization in the temperature range of 200 to 550 ° C. in the presence of 0.003 equivalents or more and 0.2 equivalents or less of lithium hydroxide and 0.7 equivalents or more of calcium hydroxide and/or calcium oxide) ) A method for producing amino Schiff base. (In the formula, n represents an integer of 4 to 6.)