DD284254A5 - PREPARATION OF CORROSION INHIBITORS - Google Patents

Abstract

The invention relates to a process for the preparation of vapor phase corrosion inhibitors, which are suitable for the protection of metallic surfaces. In this case, the organic amine component used is a mixture of amines which is the distillation feed of the fine distillation of crude N, N-dimethylcyclohexylamine (DMCHA). {Mixture of amines; economic method; Distillation fraction; Corrosion inhibitors}

Description

Field of application of the invention

The invention relates to a process for the preparation of vapor phase corrosion inhibitors (VPI = vapor phase inhibitors), which are suitable for the protection of metallic surfaces.

Characteristic of the known state of the art

It is known that VPI are substances which have a characteristic vapor pressure at normal temperature and which have the ability to protect metal surfaces from corrosion. The most effective compounds for protecting the surfaces of iron, steel, alloys in non-ferrous metals are derived from amines:

In this formula mean:

R ₁ : H, C, -C, _2- alkyl, cyclohexyl, methylcyclohexyl, dimethylcyclohexyl, polyoxyalkylene glycols of the degree of polymerization η = 1 to 5,

Toluyl, xylene, benzyl.

R ₂ : One of the groups mentioned under R ₁ , where R) and R _{2 may be} both identical or different. R ₃ : one of the groups mentioned under R ₁ , where R ₁ , R ₂ and R ₃ can be both identical or different, but R ₃ can not be H and C ₁ to C ₂ -alkyl,

R ₂ and R ₃ may also form, together with the N atom, a 5- to 7-membered, saturated or unsaturated ring which may optionally be a structural element of, for example, an indole or imidazole derivative.

These amino acids are converted into salt-like compounds, which then represent the effective VPI. The reactants of the amines are preferably weak acids, such as nitrous acid, phenol, nitrophenols, dinitrophenols, benzoic acid, nitrobenzoic acid, dinitrobenzoic acids, but also linear and branched, saturated and unsaturated carboxylic acids and hydroxycarboxylic acids having not more than 8C atoms. A detailed overview of the variety of possibilities that this group of VPI offers in terms of synthesis and applications can be found in I. L. Rosenfeld, "Inhibitors of Atmospheric Corrosion", Verlag Wissenschaft, Moscow, 1985.

The structural diversity of the VPI allows it to be adapted to the corrosive conditions and to the metal surfaces to be protected against corrosion. In the vast majority of cases uniform connections are used. US Pat. No. 4,717,541 uses the reaction product of cyclohexylamine and / or a mixture of cyclohexylamine / dicyclohexylamine with trifluoroethanol as corrosion inhibitors. Much rarer mixtures of VPI are described, as is the Beispieisv / eise in DE-OS 2 356888 the case. According to this publication VPI be called on porous carriers, including salts of cyclohexylamine, diethanolamine, triethylenamine, benzylamine, ethanolamine and dicyclohexylamine individually, as VPI mixtures hexamethyleneimine and dicyclohexylamine or diethanolamine and dicyclohexylamine. Defined mixtures of VPI are also named by Rosenfeld. They are today market products.

Object of the invention

The object of the invention is to produce effective corrosion inhibitors in an economical manner without great technological effort.

-2- 284 254 Explanation of the nature of the invention

The invention is to achieve the objective of the object ₍ VPI produce that a characteristic vapor pressure

own and delay the corrosion of metal surfaces.

According to the invention the object is achieved in that a mixture of amines of the following gas chromatically determined composition

N, N-dimethylcyclohexylamine at most 950 g / 1000 g mixture

Cyclohexyamine at least 20 g / 1 000 g mixture

N-methylcyclohexylamine at least 100g / 1 OOOgmixture

Process-related inert foreign substances at most 100 g / 1 COOg mixture

with weak acids such as nitrous acid, phenol, nitrophenols, dinitrophenols, benzoic acid, nitrobenzoic acid, dinitrobenzoic acids, linear or branched, saturated or unsaturated carboxylic acids

The amine mixture, which is reacted with the exemplified acids to effective VPI, is the distillation forerun, which is obtained in the fine distillation of crude N, N-dimethylcyclohexylamine.

In the literature, CPIs that are used as pure substances are described far more often al? Mixtures of substances that act as VPI. In the case of the mixtures, they are in any case well-defined and, in their effect, mutually compatible mixtures of chemically largely uniform compounds. It was surprising and unforeseeable for a person skilled in the art that a distillation feed with a very complex composition, when reacted with one of the abovementioned acids, leads to a product which, in its effect as VPI, corresponds to the described prior art.

A further advantage of the method according to the invention is that a forced-on product whose disposal is complicated is converted into a valuable substance in a simple manner.

The invention will be explained in more detail with the following exemplary embodiments:

embodiments

Embodiment 1

To ensure the equivalent reaction, the amine number of the amine mixture is determined titrimetrically.

3g of a distillation of the composition (gas chromatography)

N, N-dimethylcyclohexylamine 722 g / 1 000 g mixture of cyclohexylamine 36 g / 1 000gmixture

N-methylcyclohexylamine 178g / 1 OOOgmixture of foreign substances 64 g / 1000 mixture

are mixed with 4.3 g of o-nitrophenol and heated to about 353K. The reaction proceeds quantitatively and an orange oil is formed.

Embodiment 2

3g of a distillation forerun acc. Embodiment 1 is mixed with 5.6 g of dinitrophenol and heated to about 353K. It forms a deep red oil.

Ausführungsbelsple! 3

3g of a distillation forerun acc. Embodiment 1 are mixed with 6.5 g of dinitrobenzoic acid dissolved in 100 ml of water. It drops a yellow crystalline precipitate, which is quickly filtered and dried.

Embodiment 4

To test the effectiveness of gem. Embodiment 1 to 3 prepared corrosion inhibitors commercially available steel wire nails are degreased with perchlorethylene, etched with 10% hydrochloric acid and rinsed with methanol and dried and placed in a tightly closing glass container (desiccator). This container contains a damp cotton cloth or moist pulp and optionally a piece of filter paper about 10 cm × 10 cm in size, which is impregnated with the oily inhibitors or 1 g of the solid substance to be tested for inhibitor action. The container is tightly closed and left at 298 to 328 K for 72 hours. Thereafter, the surface of the steel nails is assessed

 This quick test gave the following result:

without inhibitor nails evenly rusted

Inhibitor acc. Example 1 Nails without rust

Inhibitor acc. Example 2 Nails without rust

Inhibitor acc. Example 3 Nails without rust

commercial inhibitor nails without rust

(Inhibitor DNP from VEB Spezialchemie Leipzig)

Claims (2)

1. A process for the preparation of Korrosionshinibitoren by per se known equimolar reaction of organic amines with z. As nitrous acid, phenol, nitrophenols, dinitrophenols, benzoic acid, nitrobenzoic acid, dinileic, linear or branched or saturated or unsaturated carboxylic acids and hydroxycarboxylic acids with not more than 8C atoms to salts that have a characteristic vapor pressure and the corrosion of metal surfaces retarding, characterized in that the organic amine component is a mixture of amines of the composition: N, N-dimethylcyclohexylamine at most 950 g / 1000 g mixture Cyclohexylamine at least 20 g / 1 000 g of mixture N-methylcyclohexylamine at least 100g / 1 000g mixture Process-related inert foreign substances maximum 100 g / 1 000 g mixture is used. 2. The method according to claim 1, characterized in that is used as the amine component of the distillation forerun the Feiesti-dilation of Ν, Ν-dimethylcyclohexylamine without further purification for the synthesis of the compounds suitable as corrosion inhibitors.