DE1621581B2 - Stripping of tinplate waste to be detinned - Google Patents

Description

In addition to smelting tin ore, recovery plays a role in the production of metallic tin of the metal from scrap of tinned iron sheet, so-called tinplate, an essential one Role.

The recovery of tin from tinplate waste, which used to be after the chlorine detinning process took place, is now essentially a single-stage electrolytic process in alkaline Medium or two-stage by removing the tin with the help of sodium hydroxide solution in the presence of oxidizing agents and then carried out electrolytic deposition of the tin.

The detinning of lacquered tinplate waste according to the method just mentioned is compared to the Processing of non-lacquered, tinned iron sheets, depending on the lacquer application, sometimes with considerable Disadvantages associated.

For example, in the case of the immediate detinning of painted tinplate waste, without suitable pretreatment, poorer detinning, inevitably associated with poorer scrap quality, additional Consumption of oxidizing agents and, last but not least, higher expenditure of time and energy accepted will.

The invention is therefore based on the object of creating a method which makes it possible to apply layers of lacquer to be detached from the tinplate and a cheaper one in both the one-step and two-step process To ensure detinning and a higher quality scrap. ; ; ; ·.:> ·; ■; . ■ ■■■ '■■. ■; '

The use of a solution consisting of sodium hydroxide and / or sodium carbonate, 0.1 to 2 percent by weight of compounds of the general formula

HOC ₂ H ₄ OC ₂ H ₄ OR,

where R is an alkyl radical with 1 to 4 carbon atoms, the remainder is water, for paint stripping to detinning tinplate waste, the detinning and the recovery of the tin in itself be carried out in a known manner, proposed. In contrast, it has now been found that a considerable larger number of alkylene glycol ethers suitable for removing lacquer layers from tinplate is. ■ '..... ■'

The present invention is characterized by the use of a solution made up of sodium hydroxide and / or sodium carbonate, 0.05 to 1 percent by weight of compounds of the general formula

R ¹

■ O - [CH ₂ - CHR ² - O -] _e H

ίο in which R ^{1 is} an alkyl, aryl, alkaryl or aralkyl radical and R ^{2 is} a methyl or ethyl radical or a hydrogen radical and χ is any number from 1 to 25, excluding those compounds in which R ¹ is an alkyl radical with 1 to 4 carbon atoms, R ^{2 is} a hydrogen radical and χ = 2 , and there is water for the stripping of tinplate waste to be detinned, the detinning and the recovery of the tin being carried out in a manner known per se.

ao If R ^{1 is} an alkyl radical, this can, for. B. have the meaning of a methyl, ethyl, propyl, isopropyl, pentyl, octyl or dodecyl radical. If R ^{1 is} an aryl radical, the phenyl radical is preferred. The octylphenyl, nonylphenyl and dodecylphenyl radicals are preferred as alkaryl radicals. The radical derived from benzyl alcohol may be mentioned as an example of an aralkyl radical. The alkylene glycol ethers can be _her- in a manner known per se by addition of alkylene oxides to the corresponding hydroxy compounds

place. Particularly suitable alkylene oxide are ethylene oxide and propylene oxide. Mixtures of different alkylene oxides can also be added on. In such a product, R ^{2 can} e.g. B. have both the meaning of a methyl radical and a hydrogen atom.

The forces acting on the painted tinplate solutions should preferably have a temperature between 50 and 100 ⁰ C.
Depending on the type of paint and the compound used, different paint stripping times are required. In the course of the action of the solutions to be used according to the invention, the lacquer coatings are influenced physically and chemically in such a way that the lacquers easily come off the tinplate after a sufficient exposure time.

The use according to the invention of the solutions can be used both in the two-stage and in the single-stage Detinning process take place. In the two-stage process, the painted tinplate waste is first treated with the solution containing sodium hydroxide and / or sodium carbonate. Was there it is surprising for the person skilled in the art that even such extremely dilute solutions are sufficient, to attack the paint so far that it takes place in a second stage alkaline detinning in the presence of oxidizing agents, which involves electrolysis of the stannate solutions to recover the tin is downstream, allows. However, the use of those according to the invention is particularly economical Solutions for one-step, alkaline-electrolytic detinning. Even if the solubility of the previous Compounds in the detinning liquors is lower than in pure water, but it is sufficient to produce a To enable paint stripping within a technically sensible time.

A fully sufficient time is achieved during the usual detinning times of two or more hours Paint stripping. Since the connections are

3 4

tin lye also during the electrolysis prak- nungsbad, content 45 1, in which a lye (76 g

table are not attacked, only the for the NaOH / I, 50 g Na ₂ CO ₃ / l, 7 g Sn / 1 and 2 g polyoxy

actual paint stripping required amount of this ethylene butyl ether [butyl pentaglycol]) pumped around

bonds are added to the detinning liquors. is brought. The one with painted tinplate waste

In this one-step process it had to be the 5 filled iron basket during the electrolysis

Those skilled in the art are particularly surprised that not only the anode, while two iron sheets are cathodes. To

small amount of alkylene glycol monoethers effective 2-hour electrolysis (current density: 100 amps / m ²

is, but that, in addition, the electrolysis is not cathode surface) at 95 ° C is the residual tin content

is hindered, be it by oxidation of the paint-removing sheet metal scrap originally varnished 0.01% Sn.

Kungsmittel, be it by precipitation or by io

Potential shifts at the cathode, as shown in the comparison test

z. B. of surface-active compounds from the It is according to Example 2, but without polyoxy

Polarography is known. ethylene butyl ether, worked. After 2 hours of elec-

The teaching according to the invention could the USA.- trolysis, the residual tin content is 0.77%.
Patent specification 2 710 843 cannot be taken because 15 _.
corresponding to the subject matter of this patent specification with B e 1 s ρ ι e 1 3
Tinned metal sheets coated with siloxane resins with 2 kg of lacquered tinplate waste with 1.07% Sn, practically anhydrous alkyl glycol compounds, are processed as indicated in Example 2 (current lacquer. Working in an aqueous phase, the density: 200 Amp./ m ² cathode area); However, the lye detinning of the tinplate and the recovery 20 stops instead of 2 g of polyoxyethylene butyl of the tin is not the subject of this patent specification. ether 1 g polyoxyethylene phenyl ether / 1. After 2 hours

Although the USA. Patent 3,168,477 relates likewise ended electrolysis at 75 ⁰ C, the Restzinngehalt,

if the paint stripping of tinplate waste in the case of the originally painted tinplate waste Ό, ΙΙ% ·? ' two-stage alkaline chemical paint stripping. Development

According to this patent specification, however, solutions are 25 comparative experiment
used for paint stripping, which condensed aroma It is carried out according to Example 3, but without polyoxytic ring systems, preferably those with two ethylene phenyl ethers. After 2 hours of eleic rings and small amounts of surface-active trolysis, the residual tin content is 0.65%
Substance that is both wetting and emulsifying. .
shafts used. The main weight of these 30 B e ι s ρ 1 e 1 4
The patent is based on the use of naphthalene 2 kg of lacquered tinplate waste with 1.07% Sn and its mono- and polyalkylated compounds. processed as indicated in Example 2 (current-these, however, hinder the deposition of the tin at a density: 200 amps / m ² cathode area); the lye or the subsequent electrolysis. In contrast to the teaching, however, instead of 2 g of polyoxyethylene butyl, this patent specification consists of 35 ethers of 1 g of polyoxyethylene nonylphenyl ether / l. After using a solution of fewer components and 2 hours of electrolysis at 75 ° C, the residual tin is ensured that this solution is not only at the level of the originally painted tinplate waste, a two-stage detinning process, but also at 0.41%.

the single-stage direct electrolysis can be used

can. 40 ■

The object of the present invention is to be carried out according to Example 4, but without polyoxy-

the following examples are explained in more detail, ethylene nonylphenyl ether, worked. After 2 hours

in these experiments polyoxyethylene butyl electrolysis the residual tin content is 0.65%.

ether (butyl pentaglycol) and polyoxyethylene benzyl. ..

ether prove to be particularly effective. , 45 examples

.... 2 kg of painted tinplate waste with 0.27% tin

Example 1 are placed in an iron basket in an iron

200 g of lacquered tinplate waste with a 0.48% tin bath, content 45 liters, in which a lye (76 g

put in a suitable glass or iron vessel NaOH / l, 50 g Na ₂ CO ₃ / l, 7 g Sn / 1 and 2 g polyoxy

2 hours with 21 paint stripping solution, which pumped 10 g of polyethylene benzyl ether [benzyl pentaglycol]) around

oxyäthylenbutyläther (butylpentaglycol) and 70 g is brought. The one with painted tinplate waste

NaOH / l contained, heated ^{to 100 ° C.} 'The filled iron basket is during the electrolysis

After the treatment, the tinplate waste becomes the anode, while 2 iron sheets are the cathode. To

by treatment with a lye for 2 hours, the 80 g of 2-hour electrolysis (current density: 100 amp./m ²

Contains NaOH / 1 and 15 g NaNOa / l, tinned. The remaining 55 of cathode area) at 75 ⁰ C, the Restzinngehalt

The tin content of the tinned iron sheet is 0.05% of the originally painted sheet metal waste 0.012% Sn.

Sn.

Comparative experiment

Comparative experiment. , ".. '. ,,, ^,

It is according to Example 5, but without polyoxy

200 g of lacquered tinplate waste with 0.48% tin 60 ethylene benzyl ether, worked. After 2 hours of elec-

if trolyse without treatment with a paint stripping solution, the residual tin content is 0.19% Sn.

directly with a lye containing 80 g NaOH / 1 and 15 g ·.

NaNO ₂ /! contains, tinned. The residual tin content in example 6

carries 0.35% Sn. 2 kg of painted tinplate waste with 0.27% tin

... 65 are put in an iron basket in an iron fuel

U e s 1 e ρ 1 1 I nungsbad, capacity 45 1, in which a liquor (76 g

2 kg painted tinplate waste with 0.85% tin NaOH / 1, 50 g Na ₂ CO ₃ / l, 7 g Sn / 1 and 2 g polyoxy

are pumped in an iron basket into an iron de-tin- ethylene-oxypropylene-butyl ether),

brought. The iron basket filled with painted tinplate waste is the anode during the electrolysis, while 2 iron sheets are the cathode. After 2 hours of electrolysis (current density: 100 amps / m ^{2 of} cathode surface) at 75 ° C., the residual tin content of the originally painted sheet metal waste is 0.016% Sn. Comparative experiment

It is according to Example 6, but without polyoxyethylene-oxypropylene-butyl ether worked. After 2 hours of electrolysis, the residual tin content is 0.19% Sn.

Claims (1)

Claim: Use of a solution consisting of sodium hydroxide and / or sodium carbonate, 0.05 to 1 percent by weight of compounds of the general formula R ¹ - O - [CH ₂ - CHR ² - O -] * Η in which R ^{1 is} an alkyl, aryl, aralkyl, alkaryl or aralkyl radical and R ^{2 is} a methyl or ethyl radical or a hydrogen radical and χ is any number from 1 to 25, the compounds being excluded in which simultaneously R ^{1 is} an alkyl radical with 1 to 4 carbon atoms, R ^{2 is} a hydrogen radical and χ = 2 , and there is water for the stripping of tinplate waste to be detinned, the detinning and the recovery of the tin being carried out in a manner known per se.