Recycling of flux material

Details Recycling of flux material Recycling of flux material

1999-05-25

2001-03-27

Dunn, Tom (Department: 1754)

Chemistry of inorganic compounds

Halogen or compound thereof

Hydrogen halide

C423S484000, C423S465000, C252S183140, C106S461000

Reexamination Certificate

active

06207125

ABSTRACT:

BACKGROUND OF THE INVENTION
The invention relates to the recycling of flux residues from soldering processes using solders composed of metal fluoroaluminates and fluorozincates.
As used herein, the term “soldering” includes both soft soldering and hard soldering (i.e., brazing).
In soldering, in particular of aluminium and aluminium alloys, fluxes composed of metal fluorometallates, e.g. composed of alkali metal fluorozincates and particularly of alkali metal fluoroaluminates, are used. Fluoroaluminates which contain potassium and/or cesium are particularly well suited. A considerable amount of the flux used for soldering is not consumed, but remains in the pipes, lines or apparatus. A further portion of the residues results from any cleaning of the soldered objects which may be carried out, from spent flux suspensions and from the regularly-performed cleaning of storage tanks. In the past these flux residues have not been re-used.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a process with which profitable re-use of the flux residues is possible.
This and other objects of the invention are achieved in accordance with the present invention by providing a method of recycling residue of an alkali metallate flux for soldering aluminum, the flux comprising at least one alkali metallate selected from alkali metal fluoroaluminates and alkali metal fluorozincates, the method comprising admixing the flux residue with fluorspar, and reacting the admixed fluorspar and flux residue with sulfuric acid or oleum to produce hydrogen fluoride and anhydrite.
According to a further aspect of the invention, the objects are achieved by providing a composition of matter useful as a reactant in the production of hydrogen fluoride, the composition comprising an admixture of fluorspar and a residue of an aluminum soldering flux comprising at least one alkali metallate selected from the group consisting of alkali metal fluoroaluminates and alkali metal fluorozincates.
In yet another aspect of the invention, the objects are achieved by providing anhydrite containing potassium sulfate and aluminum sulfate produced by treating a potassium fluoroaluminate containing flux residue according to the method described above.
The invention is based on the discovery that the flux residues can advantageously be added to the fluorspar, which is reacted with oleum to form hydrogen fluoride and CaSO
4
.


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