CH623332A5 - Process for the preparation of sodium lactamoaluminates - Google Patents

Description

The invention relates to a process for the preparation of sodium lactam aluminates of the general formula (I)

Na Al (0CH2CH20CH3) x L4-x (I),

where x is in the range from 0 to 2 and L represents the residue formed by splitting off the active hydrogen from the lactam, which is of the general formula

-N- (CH2) n-CO,

where n is 3 to 11.

The best known compounds of lactams with metals are lactamates of alkaline metals, which are used as initiators of anion polymerization and which are obtained by reactions of the lactams with alkaline metals, their hydrides, hydroxides, or their alcoholates. The use of the lactamates of alkaline metals for initiation is complicated, however, because the water and / or the alcohol must be removed from the reaction mixture by distilling off the lactam feed at reduced pressure.

The above-mentioned shortcomings are not expressed when sodium lactam aluminates are used as initiators of the anion polymerization, which, however, have so far not been produced industrially.

It was therefore found to be expedient and advantageous to look for a technically and economically effective process for the production of sodium lactam aluminates.

The process according to the invention for the preparation of the sodium lactam aluminates of the general formula (I)

Na AI (0CH2CH20CH3> L4-x (I)

is defined in claim 1.

The invention takes advantage of the knowledge that according to the working method of this invention, sodium lactamates are produced during a single operation by slowly metering sodium hydride aluminate or sodium amino aluminate into excess lactam, whereby hydrogen or ammonia are released. During this process, no corresponding azacycloalkanes, which act as inhibitors of the polymerization of the lactams, are formed by reduction, and the reduction may not exceed the value of 1%.

From an economic point of view, it is advantageous

if only NasAlHfi or NaAl (NH2) 4 is used in the production according to the invention.

The hydrides NaAfflU and Na3AlH6 can be dosed to the lactam as a suspension, which can be prepared by direct synthesis from sodium, aluminum and hydrogen, whereby no isolation needs to be carried out. Only after the reaction with the lactam is the unreacted aluminum filtered off and a solution of the product obtained.

In the case that NaAlHt is used, this hydride can also be added in ether solution or in such a way that the reaction is carried out at the boiling point of the solvent, which is a mixture of an aromatic hydrocarbon with ether. The NaAlHt is extracted by the reflux of the evaporating solvent. The rate of dosing of NaAlH4 depends on the amount of ether added.

The sodium dihydrido-bis (2-methoxyethoxo) aluminate, which is commonly produced industrially, is usually dosed in toluene solution.

The sodium tetraaminoaluminate used as the starting material is obtained according to a procedure described by F.W. Bergstrom (J. Am. Chem. Soc. 45 [1923] 2788) and R.Brec and J.Rouxel (C.R. Acad. Sei. Ser. C 264 [1967] 512) were prepared from sodium, aluminum and ammonia.

The composition of the end product is given by the choice of the aluminates from which it is assumed. When using sodium dihydrido-bis (2-methoxyethoxo) aluminate, sodium dilaktamo-bis (2-methoxy-ethoxo) aluminates are formed; when using NaAlHi, Na3AlHs or NaAl (NH2) 4, sodium tetralactamoaluminates are formed. In the event that a mixture of sodium dihydridobis (2-methoxyethoxo) aluminate with one of the aluminates mentioned is used as the starting material, the end product is a sodium lactam aluminate of the general formula

NaAl (0CH2CH20CH3) xL4-x,

where x and L have the same meaning as described above. The finite composition (the size of the index x) is given by the molar representation of the starting aluminates and the sodium lactam aluminates resulting from them, as stated in the following equation.

xNaAl (0CH2CH20CH3) 2L2 + (2-x) NaAl Lt-s »

2 NaAl (0CH2CH20CH 3> L4-x

The compounds represented by this invention are soluble in aromatic hydrocarbons and are useful as catalysts for anion polymerization of lactams. Lactam is released through its reaction with the water present in the lactams, so that the polymerization with these compounds does not necessarily require an anhydrous environment, as in the case of sodium lactamates.

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Some examples of the practice of the invention are further described.

example 1

565 g of 6-caprolactam (5 mol) were placed in an inert atmosphere in a two-liter three-necked flask equipped with a stirrer, water-cooled reflux condenser and a dropping funnel, and 300 ml of toluene were added. A solution of NaAlH-i in dimethoxyethane was added over the course of 3 hours, with the evolution of hydrogen. The NaAlHU solution was obtained by dissolving 56.6 g of 98% NaAlEU (1.02 mol) in 350 ml of dimethoxyethane. After adding this solution, the dropping funnel was rinsed with 60 ml of dimethoxyethane and the resulting solution was added to the reaction mixture. The solution after the reaction was clear and pale yellow in color. This solution, thickened by evaporation of part of the solvent, gave 877.4 g of a 57.5% sodium tetrakaprolactamoaluminate solution.

Example 2

51 g of pyrrolidone (0.6 mol) were placed in an inert atmosphere in a 250 ml flask equipped with an extraction attachment (glass frit) and water-cooled reflux condenser, and 30 ml of toluene and 30 ml of tetrahydrofuran were added. 5.7 g of 98% NaAlHt (0.103 mol) were placed in the extraction head. The reaction mixture was then heated to boiling and the NaAlHU was metered in by slow extraction, during which hydrogen evolved. After all NaAIHU had been extracted, a clear, slightly yellowish solution was obtained which, after evaporation of part of the solvent, weighed 76.3 g and contained 52% sodium tetrapyrroli-donoaluminate.

Example 3

98.5 g of 12-laurolactam (0.5 mol) were placed in a 500 ml three-necked flask equipped with a stirrer, water-cooled reflux condenser and dropping funnel, and 120 ml of toluene were added. With stirring at the boiling point, a solution of 5.4 g of 98% NaAlH4 (0.098 mol) in 40 ml of dimethoxyethane was added dropwise to the solution over the course of two hours. The reaction proceeded with the evolution of hydrogen. After the reaction was complete, a clear, slightly yellowish solution was obtained which, after evaporation of part of the solvent, weighed 190 g and contained 43% sodium tetralaurolactamoaluminate.

Example 4

53.5 g of e-caprolactam (25% excess) and 25 ml of toluene were placed in a 250 ml three-necked flask equipped with a stirrer and water-cooled reflux condenser. A suspension of 5.75 g of powdered NaAlH4 (98.8%) in 50 ml of toluene was added continuously to this mixture over the course of 2 hours. The suspension was obtained by constant stirring and metered in using pressure nitrogen through a polyethylene capillary. Residues of the suspension were introduced into the reaction mixture by rinsing the vessel with 10 ml of toluene. Hydrogen and heat developed during the reaction. 135 g of solution were obtained, which contained 38.9% sodium tetracaprolactam aluminate.

Example 5

126 g of ra-laurolactam (20% excess) and 250 ml of benzene were placed in a 1000 ml three-necked flask equipped with a stirrer and water-cooled reflux condenser. To this mixture was added 100 ml of a suspension with stirring, which contained 10.18 g of 89% Na3AIH6, which was prepared by direct synthesis from sodium, aluminum and hydrogen. The Na3AlH6 suspension was added in the same manner as in Example 4 over 2.5 hours. It was rinsed with 20 ml of benzene. The reaction mixture was cooled, filtered and the filter cake washed with 20 ml of benzene. The overall yield was 461 g of solution containing 16.07% sodium tetralaurolactamoaluminate.

Example 6

68 g of y-butyrolactam (15% excess) were placed in a 250 ml three-necked flask equipped with a stirrer and reflux condenser. A suspension of 11.72 g of Na3AlHß (98.5% strength) in 100 ml of toluene was added dropwise to the liquid lactam (30 ° C.). The dropwise addition to the reaction mixture lasted 3 hours and proceeded in a similar manner as in Example 4. Residues of Na3AlH6 were brought into the reaction mixture by washing out the metering device with 20 ml of toluene. Hydrogen and heat developed during the reaction. 174 g of solution were obtained, which contained 25.0% sodium tetrabutyrolactamo-aluminate.

Example 7

1709 g of e-caprolactam and 600 ml of toluene were placed in a 61 three-necked flask with stirrer and reflux condenser. The reaction mixture from the direct synthesis of NaAIH4 in toluene was added dropwise to this suspension with stirring. 1800 g of this mixture, which contained 7.89% NaAfflU, 2.1% Na3AlH &, 3.36% NaAlH2 (0CH2CH20CH3), 2.2.5% Al and other solid impurities, were added over the course of 3 hours. Hydrogen evolved during the reaction. After cooling, the reaction mixture was filtered and the filter cake was washed with 200 ml of toluene. In total, 4100 g of filtrate containing 2.16% Al, which was a mixture of dissolved sodium tetra-caprolactam aluminate (36.23%) and sodium dikaprolak tam-bis (2-methoxyethoxo) aluminate (3.08%) and one Yield corresponds to 99.5%, won.

Example 8

1832 g of e-caprolactam (20% excess, calculated on the hydride) and 830 ml of toluene were placed in a 61 flask with reflux condenser, an effective stirrer and a 21 dropping funnel. 1949 g of 70% sodium dihydridobis (2-meth-oxyethoxo) aluminate was added dropwise to this suspension over 2.5 hours with stirring. Hydrogen evolved in the course of the reaction and the mixture warmed up to 85 ° C. 4450 g of a clear solution were obtained, which contained 64.35% sodium dikaprolaktamobis (2-meth-oxyethoxo) aluminate.

Example 9

255.4 g of a-pyrrolidone (y-butyrolactam) (50% excess) were placed in a 1000 ml V flask with reflux condenser and stirrer. 288.6 g of a 70% strength solution of sodium dihydridobis (2-methoxyethoxo) aluminate in toluene were added to the molten a-pyrrolidone at 30 ° C. over the course of 3 hours with stirring. During the reaction, hydrogen evolved and the reaction mixture warmed to 80 ° C. 530 g of a clear liquid were obtained, which contained 69.5% sodium dibutyrolactamobis (2-methoxyethoxo) aluminate.

Example 10

70 g of oj-laurolactam (20% excess) and 150 ml of benzene were placed in a 500 ml flask with reflux condenser and stirrer. 44.1 g of a 65% solution of sodium dihydridobis (2-methoxyethoxo) aluminate in benzene were added dropwise to the mixture over the course of two hours. The solution obtained weighed 300 g and contained 28.03% sodium dilaurolakta-mo-bis (2-methoxyethoxo) aluminate.

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Example 11

12.2 g of 97.5% NaAl (NH2) 4 (0.1043 mol) and 25 ml of benzene were placed in a 500 ml flask equipped with a dropping funnel and a reflux condenser, which was sealed with a drying tube filled with solid KOH. To this mixture was added 196.5 g of a 30% solution of 6-caprolactam (0.522 mol) in benzene and then heated in a boiling water bath for half an hour. Ammonia evolved during the reaction. In order to remove this, the mixture was barbotted with 41 dry nitrogen for 20 minutes. 196 g of a 26.5% solution of sodium tetrakis (6-kaprolaktamo) aluminate were obtained.

Example 12

6.35 g of 97.5% NaAl (NH2) 4 (0.0596 mol) and 20 ml of toluene were placed in a 250 ml flask with a reflux condenser, which was closed with a drying tube filled with solid KOH. Using the dropping funnel, 70.9 g of a 50% solution of 4-butyro-

lactam (0.417 mol) added. The reaction mixture was then heated in a boiling water bath for 45 minutes. After cooling to 20 ° C, the mixture was evacuated until the vacuum reached 20 Torr. 82.1 g of a 23% strength solution of sodium tetrakis (4-butyrolaktamo) aluminate were obtained.

Example 13

In a 250 ml flask with a reflux condenser, which was sealed against 10 atmospheric humidity with a drying tube filled with solid KOH, 4.52 g of 97.5% NaAl (NH2) 4 (0.0423 mol) and 20 ml of benzene were placed submitted. 115.7 g of a 32.5% solution of 12-laurolactam in benzene were added to this mixture over 45 minutes. 15 The mixture was then heated in a boiling water bath for 50 minutes. After the reflux condenser was replaced for a Lie cooler, 35 ml of benzene was distilled off from the reaction mixture. 97 g of a 36.4% solution of sodium tetrakis (12-Iaurolaktamo) aluminate 20 were obtained.

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Claims (2)

623 332 2 PATENT CLAIMS 1. Process for the preparation of sodium lactam aluminates of the general formula I Na AI (0CH2CH20CH3) x L-4-x (I), in which x is in the range from 0 to 2 and L is the radical of the general formula formed by splitting off the active hydrogen from lactam -N CO L (CH2) n means in which n has a value from 3 to 11, characterized in that in an aromatic hydrocarbon excess lactam of the general formula LH, in which L has the meaning given above, with at least one compound from the group NaAlH4, Na3AlH6, NaAlH2 (0CH2CH20CH3) 2 and NaAl (NH2) 4, the molar ratio of the lactam to the hydridic hydrogen H ~ or to the (NH2) group being reacted of the aluminates listed is 1: 1 to 2: 1. 2. Sodium lactam aluminates of the general formula I Na Al (0CH2CH20CH3) x L * -x (I), produced by the method according to claim 1.