DE1771842C3 - Corrosion inhibitor - Google Patents

Description

Manufacture of tetrahydrobenzotriazole

174 parts of pure benzotriazole. suitable for photographic purposes, were dissolved in 1000 parts of ethanol and shaken with 10 parts of Raney nickel hydrogenation catalyst for 30 minutes. This solution was then filtered to remove the catalyst, and the filtrate was placed in a pressure reactor equipped with an effective stirrer and a device for recording the internal temperature. 1.0 part of a rhodium / animal charcoal catalyst containing 5% by weight rhodium was also placed in the reactor. The reactor was filled with hydrogen up to a pressure of 130 atmospheres and then ^{heated to an internal temperature of 100 °} C. while the contents of the reactor were stirred vigorously.

After the hydrogenation was completed, as indicated by this; that the pressure in the reactor is no longer continued to drop, the reactor is hot to cool to 25 ° C. After the excess hydrogen had escaped, the reaction mixture was filtered to remove the catalyst to remove, and the filtrate was evaporated to dryness

In this way, 160 parts (89% of theory) of a white solid substance were obtained. Recrystallization this solid from water gave 140 parts (87.5% recovered) 4,5,6,7-tetrahydrobenzotriazole as white crystalline needles with a melting point in the range of 82 ° C to 85 ° C and with the following elemental analysis:

Found

Calculated
(RIrC ₆ H ₉ N ₃ )

C: 58.6% 58.52% H: 7.27O / o 7.37% N: 33.84% 34.12%

In an analogous manner, 45 parts (99% of the theoretical yield) were obtained from 50 parts of N-hydroxybenzotriazole obtained a white solid substance, 4,5,6,7-tetrahydrobenzotriazole when recrystallized from water gave white crystalline needles of melting point 82 ° C to 85 ° C.

Tetrahydrobenztriazole has valuable corrosion-inhibiting properties when applied to metal surfaces Anti-fogging or other protective properties. It can also be called metal corrosion or Fog inhibitor used in functional materials that come into contact with metal surfaces to be brought.

Examples of functional materials into which tetrahydrobenzotriazole can be incorporated, include natural and synthetic lubricants, hydraulic fluids, varnishes, and wax polishes polymeric substances such as rubber, polypropylene, polyvinyl chloride and acrylonitrile / butadiene / styrene terpolymer; and aqueous media, e.g. aqueous ethylene glycol or other glycol-containing compositions, which are used as antifreeze agents, or other cooling mixtures and aqueous detergents or cleaning compositions, especially those compositions that are partially or wholly composed of Polyphosphate, a per compound or a polyamino-polycarboxylic acid exist.

Tetrahydrobenztriazole is therefore a valuable additive for natural and synthetic lubricant compositions, z. B. in compositions in which one has the presence of an antioxidant wishes that, such as B. dioctyldiphenylamine, tends to corrode copper or copper alloys. Because the unexpectedly good solubility of tetrahydrobenzotriazole in mineral oils, its use in such Lubricants particularly advantageous. Other applications for which Tetrahydrobenztriazol with special Advantage due to its excellent solubility properties can be used the field of white spirit based paints.

Tetrahydrobenztriazole can also be used as a metal deactivator to prevent polymeric degradation To inhibit materials in contact with metals. It can for example be used with advantage in polypropylene material

incorporated willow for use as a covering material for button wire or other copper items is determined, but would be rapidly degraded in the presence of copper.

Other metals that are deactivated by tetrahydrobenzotriazole are ice, silver or cadmium or their alloys, but it is particularly useful for copper or copper alloys.

The addition of tetrahydrobenzotriazole in the areas of application mentioned is preferably in Range from 0.01% to 10%, in particular in the range from "Ö, 1 to 5% by weight, based on the total weight of the functional material.

Metal surfaces can be treated with tetrahydrobenzotriazole to prevent corrosion or misting to protect by contacting the surface with tetrahydrobenzotriazole in the vapor phase, or by the metal surface is contacted with the tetrahydrobenzotriazole in a solution, e.g. B. in aqueous, Glycol or polyglycol solvents; the 4,5,6,7-tetrahydrobenzotriazole can be applied in any conventional way for the treatment of metal surfaces, for example by spraying a Solution, by dipping the metal in a solution, or by wrapping the metal in paper or other packaging materials that contain the inhibitor. When the metal with a solution of tetrahydrobenzotriazole is treated, the solution preferably contains a proportion of 4,5,6,7-tetrahydrobenzotriazole in the range from 0.01% to 10%, in particular in the range from 0.1 to 5% by weight, based on the Total weight of the solution.

The tetrahydrobenzotriazole protects the metal surfaces treated in this way, e.g. B. iron, silver or cadmium or their alloys but especially copper and pure alloys against discoloration (fogging) in contact with hydrogen sulfide, ammonia or any other harmful atmosphere. Besides that can be the treatment of copper or copper alloy surfaces with the tetrahydrobenzotriazole Have the effect that water vapor or other vapors can condense on it in the form of droplets. The connection is therefore used to improve the heat transfer properties of capacitors or other objects made of copper or copper alloy are valuable.

The following examples illustrate the invention without however, to limit them. The parts by weight used here are in the same relationship ^ u Parts by volume such as kilograms to liters. Unless otherwise stated, the percentages are percentages by weight.

example 1

A sample of bare, acid-dipped copper metal foil was immersed in one of the following solutions:

an aqueous benzotriazole solution at 0.1 wt% / volume; and an aqueous solution of 4A6,7-tetrahydrobenzotriazole with 0.1% by weight / Vohunen. The two immersed samples were kept at 65 ° C for 2 minutes held and then in distilled water

ίο washed and dried in hot air

The dried samples were then placed in a hot ^{oven kept at 140 °} C. and the time until visible fogging occurred was determined

The results are given in the table below. For comparison, the data are also in the Table given, which refer to a copper sample that was immersed in an aqueous solution, which did not contain any additives

20th

Example additive

Time to formation of a fog (min.)

no 10 Benzotriazole 10-15 Tetrahydrobenzotriazole 30-40

These results demonstrate the superior resistance to fogging of a copper sample treated according to the invention at elevated temperature compared to a similar sample, which had been treated with a standard fogging inhibitor.

Example 2

Two S.A.E 20 mineral oil compositions based on paraffin with a content of 0.01% by weight (maximum solubility) benzotriazole or 0.2 wt% 4,5,6,7-tetrahydrobenzotriazole were produced

Copper and steel samples were immersed in the appropriate oils, which were then heated to 170 ° C heated up and at diesel temperature for 48 hours were held while blowing air through the hot oils at a rate of 15 liters / hour let through it.

After this time had elapsed, the change in viscosity of the oils was determined and the final acid value of the oils was determined and the weight loss of the immersed samples was determined. The results obtained are summarized in the following table.

Example additive

Viscosity modification

Acid value

(Centistoks) (mg KOH / s)

Sample weight loss (milligrams) copper steel

Benzotriazole

Tetrahydrobenzotriazole 5.06

1.8
0.8

1.5 0.7

The results in the table above show that tetrahydrobenzotriazole in mineral oil medium is a much more effective corrosion inhibitor for copper and steel than benzotriazole itself, which is only weakly ii: h;

Example 3

The following dry powder compositions were prepared:

80 parts by weight of pentasodium tripolyphosphate,
20 parts by weight of sodium dodecylbenzenesulphonate

80 parts by weight of pentasodium tripolypbosphate,
1938 part by weight of sodium dodecylbenzenesulphonate, 0.02 part of benzotriazol

80 parts by weight of pentasodium tripolyphosphate,
19 ^ 8 parts by weight of sodium dodecylbenzenesulphonate, 0.02 parts of 4,5,6,7-tetrahydrobenzotriazol

From each of the compositions A, B and C were aqueous solutions containing 0.5 wt .-% / volume prepared and heated to 70 ⁰ C heated Cestecke made of nickel silver (62% Cu, 15% Ni, 23% Zn) were then placed in each of the immersed in the appropriate solutions and kept in the hot solutions for a period of three hours. The appearance of each nickel silver item was recorded periodically during this time. After 15 minutes, the items in the composition A solution had tarnished a deep yellow color, those in the composition B solution a light yellow color, while those in the composition solution C were not started.

After three hours the cutlery in the solutions of compositions A and B had one assumed deep yellow to brown color, while that in the solution of composition C showed practically no discoloration.

Example 4

Filter papers (Whatman No. 1) are so impregnated by immersion in tetrahydrobenzotriazole solutions of various concentrations and subsequent drying that a dry content of 0.25, 0.50, and \% tetrahydrobenzotriazole results.

Sheet copper strips of 3 χ 1.5 cm were CCU S degreased, dried with filter paper and placed in a gloss bath for 10 seconds (mixture of 500 ml 88-90% Phosphoric acid, 200 ml conc. Sulfuric acid and 250 ml glacial acetic acid). Then the sheets are immersed Immediately rinsed in running water with filter paper

ίο dried and - without direct contact with the Fingers - bent into a semicircle. Then it will be each sheet is wrapped in impregnated filter paper (7x7 cm) and lightly tied with cotton thread

Γη a wide-necked flask with a capacity of approx. 500 ml

is a) a smaller flask that holds 2 ml of a saturated aqueous sodium sulfate solution, and b) two parallel samples of the packed copper sheets (with the Bow up) and the flask is hermetically sealed. After 48 hours at room temperature the samples are taken and placed in a drying cabinet at 80 ° C. for 24 hours

The metal sheets were then unwound and the staining was assessed visually with 7 grades. Grade 0 means no stretching, at grade 6 the whole surface is tarnished. Here the inside and the outside of the bow judged separately

, ₀ % tetrahydrobenzotriazole (based on the weight of the paper)

Staining inside Outside

0.25
0.5
1.0

6th 6th 1 0 1 0 1 0

Claims (1)

Claim: Use of 4,5,6,7-tetrahydrobenzotriazole as a metal deactivator and as a corrosion inhibitor. The present invention relates to the use of tetrahydrobenzotriazole as a metal deactivator and Corrosion inhibitor for protecting metal surfaces, especially copper surfaces that come into contact stand with functional fluids. The use of triazole compounds and especially of benzotriazole as copper deactivators is very well known. Benztriazole has widespread use as a copper deactivator in such systems found such. B. Antifreeze solutions, synthetic ester lubricants for jet aircraft, wax polishes, Casing material for protecting copper objects, etc. So far, however, it has not been possible to successfully base benzotriazole in functional fluids to use mineral oils, as their solubility is too low It has now been found that 4,5,6,7-tetrahydrobenzotriazole is an excellent corrosion inhibitor suitable for metals, although it can also be used in solution in mineral oils Use as a metal deactivator for plastics that are in constant contact with metals, such as B. Insulation of copper wires. The present invention therefore consists in the use of 4,5,6,7-tetrahydrobenzotriazole as Metal deactivator and as a corrosion inhibitor. The 4,5,6,7-Tetrahydrobenztriazol is a known compound, for example by catalytic Hydrogenation of benzotriazole or of N-hydroxybenzotriazole can be produced. Suitable as a catalyst platinum metals, especially rhodium. Usually the catalysts are used on supports, such as B. on S1O2, AI2O3 or coal. The following Example may illustrate such a manufacturing process in more detail.