DD284255A5 - PROCESS FOR THE 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. The organic amine component used is a mixture of amines which represents the distillation residue of the fine distillation of crude N, N-dimethylcyclohexylamine (DMCHA). {Mixture of amines; economic method; Destillationsrueckstand; Corrosion inhibitors}

Description

is used.

2. The method according to claim 1, characterized in that is used as amine component of the distillation residue of the Femdestillation of Ν, Ν-dimethylcyclohexylamine optionally without further purification for the synthesis of the compounds suitable as corrosion inhibitors.

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 and non-ferrous metals are derived from amines

In this formula mean

R _{1 is} H, C ₁ -C ₁₂ -alkyl, cyclohexyl, methylcyclohexyl, dimethylcyclohexyl, polyoxyalkylene glycols of the degree of polymerization η = 1 to 5, phenyl, toluyl, xylene, benzyl

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

R ₂ and R ₃ may also together with the N-Atotn form a 5 to 7-membered, saturated or unsaturated ring, which may optionally be a structural element, for example, an indole or Imidazolderivates These amines are converted to salt-like compounds, which then represent the effective VPI The Reactants of the amines are preferably weak acids, such as the nitrous acid phenol, nitrophenols, dinitriphenols, benzoic acid, nitrobenzoic acids, dinitrobenzoic acids, but also linear and branched saturated and unsaturated carboxylic acids and hydroxycarboxylic acids having not more than 8C atoms

A detailed review 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 atomic-phase corrosion," published by Science, 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 from corrosion. In the vast majority of cases, uniform compounds are used. US Pat. No. 4,717,541 uses the reaction product of cyclohexylamine and / or a mixture of cyclohexylamine / dicyclohexylamine with toluuranol Corrosion inhibitors Mixtures of VPI are described far less frequently, as is the case for example in DE-OS 2 356888. According to this publication VPI are called on porous carriers, including salts of cyclohexylamine, diethanolamine, triethylamine, benzylamine, ethanolamine and dicyclohexylamine individually, as VPI -Mixed hexamethyleneimine and dicyclohexylamine or diethanolamine and dicyclohexylamine Defined mixtures of VPI are also called 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.

Explanation of the essence of the invention

The invention is to achieve the goal of the object to produce VPI, which have a characteristic vapor pressure and retard 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

Ν, Ν-dimethylcyclohexylamine at most 900 g / kg mixture

Ν, Ν-dimethylaniline at most 300 g / kg mixture

Ν, Ν-dicyclohexylamine at least 5Og / kg mixture

N-methyl-F ^ N-dicyclohexylamine at least 50 g / kg mixture

Process-related inert foreign substances not exceeding 100 g / kg mixture

is reacted with weak acids such as nitrous acid, phenol, nitrophenols, dinitrophenols, benzoic acid, nitrobenzoic acids, 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 residue obtained in the fine distillation of crude Ν, Ν-dimethylcyclohexylamine.

In the literature, CPIs used as pure substances are described far more often than mixtures of substances that are effective as VPIs. 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 residue with a very complex composition, when reacted with one of the acids mentioned, leads to a product which, in its effect as VPI, corresponds to the described prior art.

An advantage of the erfindungsgmäßen method further that a forced-on product whose disposal is complicated, is converted in a simple manner to a valuable material.

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. 3 g of a distillation residue of the composition (gas chromatographic)

Ν, Ν-Dimethylcyclohexylamine (DMCHA) 369 g / 1000 g of mixture

Ν, Ν-dimethylaniline (DMANL) 144 g / 1000 g mixture

Ν, Ν-dicyclohexylamine (DCHA) 95 g / 1000 g mixture

N-methyl-N, N-dicyclohexylamine (MDCHA) 62 g / 1000 g mixture

Foreign substances 80 g / 1 000 g mixture

are mixed with 2.8 g of dinitrophenol and briefly heated to about 353 K. The reaction proceeds quantitatively and a dark orange oil is formed which solidifies to yellow-orange crystals at room temperature.

Embodiment 2

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

DMCHA 650 g / 1 000 g mixture

DMANL 42 g / 1 000 g mixture

DCHA 134 g / 1000 g mixture

MDCHA 98 g / 1000 g mixture

Foreign substances 44 g / 1 000 g mixture

are mixed with 2.2 g of O-nitrophenol and briefly heated to about 353 K. It forms an orange oil that solidifies at room temperature to yellow crystals.

Embodiment 3

3g of a distillation residue acc. Embodiment 2 is mixed with 3.3 g of dinitrobenzoic acid dissolved in 10 ml of ethanol. It drops a yellow crystalline precipitate, which is quickly filtered and dried. Yield: 6.1 g

Embodiment 4

To test the effectiveness of gem. Embodiments 1 to 3 prepared corrosion inhibitors commercial steel nails are degreased with perchlorethylene, etched with 10% hydrochloric acid, rinsed with methanol and dried and placed in a tightly closing glass container (desiccator). In the container is a damp cotton cloth or

moist pulp and optionally 1 g of the substance intended for testing for its inhibitory effect. The container is tightly closed and left at 298 to 328K for 72 hours. Thereafter, the surface of the steel nails is assessed. This quick test gave the following result:

without inhibitor nails evenly rusted

Inhibitorgem. Example 1 Nails without rust marks

Inhibitor acc. Example 2 Nails without rust marks

Inhibitor acc. Example 3 Nails without rust marks

commercial inhibitor nails without rust marks

(Inhibitor DNP from VEB SpezialChemie Ueipzig)

Claims (1)

1. A process for the preparation of corrosion inhibitors by per se known equimolar reaction of organic amines with z. Nitrous acid, phenol, nitrophenols, dinitrophenols, benzoic acid, nitrobenzoic acid, dinitrobenzoic acids, linear or branched or saturated and unsaturated carboxylic acids, and hydroxy carboxylic acids having not more than 8C atoms, which have a characteristic vapor pressure and delay the corrosion of metal surfaces, characterized in that the organic amine component is a mixture of amines of the composition Ν, Ν-dimethylcyclohexylamine at most 900 g / 1 000 g of mixture N, N-dimethylaniline at most 300 g / 1000 g mixture Ν, Ν-dicyclohexylamine at least 50 g / 1000 g mixture N-methyl-N, N-dicyclohexylamine at least 50 g / 1000 g of mixture Process-related inert foreign substances maximum 100g / 1 000g mixture