CS277343B6 - Process for preparing n,n'-bis(2,2,6,6-tetramethyl-4-piperidyl)hexamethylenediamine - Google Patents

Abstract

A method of preparing N, N'-bis (2,2,6,6-tetramethyl-4- piperidylhexamethylenediamine by reaction of hexamethylenediamine with 2,2,6,6-tetramethyl-4-piperidone and with hydrogen in an aqueous medium, v the presence of a catalyst selected from the group consisting of including platinum, palladium, nickel, and cobalt, at a temperature of 50 to 100 ° C and a pressure of 1 to 15 MPa. The resulting reaction mixture was freed of the catalyst used is divided into water and organic layer at 75 to 100 ° C and organic When the layer is isolated, the final product which can be used as an intermediate for oligo- «My light stabilizers.

Description

The invention relates to a process for the preparation of N, N'-bis (2,2,6,6-tetramethyl-4-piperidyl) hexamethylenediamine. It is a known intermediate for the production of polyaminotriazine light stabilizers for synthetic polymers.

For the preparation of various N, N'-bis (2,2,6,6-tetraalkyl-4-piperidyl) diamines, the reaction of the corresponding diamine with 2,2,6,6-tetraalkylpiperidone and hydrogen under pressure and in the presence of a hydrogenation catalyst is generally used. . .

U.S. Pat. No. 4,104,248 describes a process for preparing N, N'-bis (2,2,6,6-tetramethyl-4-piperidyl) ethylenediamine using platinum supported on activated carbon as a catalyst and methanol as a solvent. The solution according to U.S. 4,605,743 is used as the hydrogenation catalyst, palladium metal or its oxide, and that of a reaction medium water, Ci to C _1Q aliphatic alcohols, _C2 to _Cg aliphatic glycols, or mixtures thereof. The solution works with the same solvents according to their mixture. The solution according to U.S. Pat. No. 4,607,104 also works with the same solvents, but it uses platinum metal, nickel or cobalt or their oxides as hydrogenation catalyst and uses 2,2,6,6-tetramethyl-4-piperidone in excess. In all the above processes, the obtained N, N'-bis (2,2,6,6-tetraalkyl-4-piperidyl) diamine is isolated from the resulting reaction mixture by filtering off the used hydrogenation catalyst and removing the solvent and impurities, including unreacted starting reactants, by vacuum by distillation.

Said known processes for the preparation of N, N'-bis (2,2,6,6-tetraalkyl-4-piperidyl) diamines, including N, N'-bis (2,2,6,6-tetramethyl-4-piperidyl) hexamethylenediamine , have several significant shortcomings. These include, in particular, considerable energy and investment intensity, related to the need for vacuum distillation of the resulting reaction mixture, the presence of significant amounts of impurities and unreacted starting materials in the final product, conditioned by close boiling temperatures, losses on the product in pre-drip, etc.

The process for the preparation of N, β'-bis (2,2,6-,6,6-tetramethyl-4-piperidyl) hexamethylenediamine by the reaction of hexamethylenediamine with 2,2,6,6-tetramethyl-4-piperidone and with hydrogen in an aqueous medium eliminates these drawbacks. in the presence of a catalyst selected from the group consisting of platinum, palladium, nickel and cobalt, at a temperature of 50 to 100 ° C and a talc of 1 to 15 MPa according to the invention.

The essence of the invention is that the resulting reaction mixture, freed of spent catalyst, is separated into an aqueous layer and an organic layer at a temperature of 75 to 100 ° C, and the final product is isolated from the organic layer by removing residual water.

The process of the invention is based on the surprising and as yet undescribed finding that N, N'-bis (2,2,6,6-tetramethyl-4-piperidyl) hexamethylenediamine is indefinitely miscible with water at a temperature of about 66.5 ° C, but at temperatures above 75 ° C it is already very slightly soluble in water. Its solubility in water at 75 ° C is 1.8%, at 80 ° C 1.2%, at 90 ° C 0.8%, at 95 ° C 0.6% and at 100 ° C 0.6%.

The process according to the invention has several remarkable advantages over known processes. These include lower energy and investment requirements, high yield and high purity of the final product - up to 99.4%, due to the significantly higher water solubility of impurities and unreacted starting reactants present in the final reaction mixture, compared to the product at temperatures above 75 ° C and lower losses on the final product.

The hydrogenation catalyst selected from the group consisting of platinum, palladium, nickel and cobalt can be used in the process according to the invention in metallic form or in oxide form, preferably supported on a suitable support such as activated carbon, alumina and the like. The final product can be isolated from the resulting reaction mixture without the need for cooling over a sufficiently wide temperature range. Its extremely high degree of purity can be further enhanced by further extraction with water. The final product can be used either directly in the liquid state or in the form of a solid melt, or in the form of a solution in a suitable solvent such as toluene and a variety of other conventional solvents. The process according to the invention can be carried out batchwise or continuously.

The following examples illustrate but do not limit the scope of the invention.

Example 1

594.68 g (3.8 mol) of 2,2,6,6-tetramethyl-4-piperidone o were weighed into a 3.75 L Paar autoclave. purity of 99.2% and 276 g (1.9 mol) of an 80% aqueous solution of hexamethylenediamine, 1600 g of water and 5.6 g of 2% Pt on activated carbon were added as catalyst. After sealing, the autoclave was purged with nitrogen followed by hydrogen and the reaction mixture was stirred for 5.5 h at 80 ° C and a talc of 1.0 MPa. After completion of the reaction and filtration of the spent catalyst, the resulting reaction mixture was separated in a separatory funnel at 80 ° C into an aqueous and organic layer, and distillation of residual water from the organic phase gave 736.0 g of N, Ν'-bis (2,2,6, Of 6-tetramethyl-4-piperidyl) hexamethylenediamine with a purity of 98.9% in the form of a very slightly colored melt with a melting point of 61.5 to 63.5 ° C, which represents a yield of 98.2%.

Example 2

598.90 g (3.8 mol) of technical grade 2,2,6,6-tetramethyl-4-piperidone with a purity of 98.5% and 368 g (1.9 mol) were weighed into a 3.75 l Paar autoclave. A 60% aqueous solution of hexamethylenediamine was added 1600 g of water and 2.3 g of 5% Pt on activated carbon as a catalyst. After sealing, the autoclave was purged with nitrogen followed by hydrogen and the reaction mixture was stirred for 2.5 h at 50 ° C and a talc of 15 MPa. After completion of the reaction, filtration of the spent catalyst and separation of the resulting reaction mixture at 99 ° C in a tempered separator into an aqueous and organic layer, the aqueous layer was discarded, 1000 g of water was added to the organic layer, and after phase separation at 95 ° C, the aqueous layer was added. abbot released. Vacuum distillation of the residual water from the resulting organic layer gave 718.0 g of N, N'-bis (2,2,6,6-tetramethyl-4-piperidyl) hexamethylenediamine with a purity of 99.2% in the form of a very faint color.

of the most crystalline solid, m.p. 62.5-64.0 ° C, which represents a yield of 95.8%.

Example 3

23.88 kg (0.15 kmol) of technical grade 2,2,6,6-tetramethyl-4-piperidone with a purity of 97.5%, 14.53 kg (0.075 kmol) of 60% were metered into a 100 l Jahndorf autoclave. of an aqueous solution of hexamethylenediamine and 25 kg of water and 84 g of 5% Pt on activated carbon were added as catalyst. After sealing, the autoclave was purged with nitrogen followed by hydrogen and the reaction mixture was stirred for 3.5 h at 100 ° C and 2 MPa hydrogen pressure. After completion of the reaction, filtration of the spent catalyst and phase separation at 90 ° C, 20 kg of water was added to the organic layer, and after phase separation at temperature, residual water was removed from the resulting organic layer by vacuum distillation to give 29.16 kg of N, N'- of bis (2,2,6,6-tetramethyl-4-piperidyl) hexamethylenediamine with a purity of 99.4% in the form of a crystalline melt with a melting point of 61.5 to 64.0 ° C, which represents a yield of 95.2%.

Claims (1)

Process for the preparation of N, N'-bis (2,2,6,6-tetramethyl-4-piperidyl) hexamethylenediamine by reacting hexamethylenediamine with 2,2,6,6-tetramethyl-4-piperidone and with hydrogen in an aqueous medium, in the presence of a catalyst selected from the group consisting of platinum, palladium, nickel and cobalt, at a temperature of 50 to 100 ° C and a hydrogen pressure of 1 to 15 MPa, characterized in that the resulting reaction mixture freed of spent catalyst is separated into an aqueous layer and an organic layer at a temperature of 75 to 100 ° C and the final product is isolated from the organic layer.