Process for the stabilization of compositions containing hydrofluoroalkanes and stabilized compositions containing hydrofluoroalkanes

Process for the stabilization of compositions containing hydrofluoroalkanes by addition of at least one salt of at least one metal chosen from lithium and/or the alkaline-earth metals in a sufficient quantity to stabilize the hydrofluoroalkanes and stabilized compositions containing hydrofluoroalkanes.

The present invention relates to a process for the stabilisation of 
compositions containing hydrofluoroalkanes as well as stabilised 
compositions containing hydrofluoroalkanes. 
The entirely halogenated chlorofluorinated hydrocarbons (CFC), suspected of 
having a harmful effect on the ozone layer, can be substituted in many 
applications, such as, for example, the use as a blowing agent for the 
preparation of foams, as a liquid coolant or as a propellant, by partially 
halogenated fluorinated hydrocarbons, also called hydrofluoroalkanes 
(HFA). 
However, the HFA are generally less stable than the CFC, so that their use 
in the abovementioned fields still poses a problem of stability. 
The subject of the present invention is to provide new efficient 
stabilising agents for hydrofluoroalkanes in the compositions which 
contain them. 
The invention relates to a process for the stabilisation of compositions 
containing hydrofluoroalkanes, characterised in that there is added 
thereto at least one salt of at least one metal chosen from lithium and/or 
the alkaline-earth metals in a sufficient quantity to stabilise the 
hydrofluoroalkanes contained in the composition. 
The term hydrofluoroalkanes is generally intended to denote the saturated 
halogenated aliphatic hydrocarbons containing at least one fluorine atom 
and at least one hydrogen atom. These hydrofluoroalkanes may or may not 
additionally contain one or more chlorine atoms. Preferably, they contain 
at/least one chlorine atom. The hydrofluoroalkanes as defined generally 
contain from 1 to 3 carbon atoms. There may be mentioned, as an example of 
such hydrofluoroalkanes, 1,1-dichloro-1-fluoroethane. 
The process according to the invention can be used for the stabilisation of 
compositions containing one or more hydrofluoroalkanes. Moreover, it can 
be used for the stabilisation of compositions consisting essentially of 
one or more hydrofluoroalkanes. 
Among the alkaline-earth metals, there are used, in particular, magnesium, 
calcium, strontium and barium. More particularly, magnesia, calcium or 
strontium, and preferably magnesium or calcium, is chosen. Excellent 
results have been obtained with calcium. 
The salts used can be organic or inorganic salts. Among the inorganic 
salts, there may be used, in particular, nitrates or halides. Among the 
latter, fluorides, bromides or chlorides are more particularly retained. 
Excellent results have been obtained with chlorides. 
Stabilising salts according to the invention can be used in the anhydrous 
or hydrated form. They are preferably used in the solid state. 
The stabilising salts according to the invention can be used at variable 
doses. They are generally used at a content of at least 0.05% by weight 
with respect to the total weight of hydrofluoroalkanes contained in the 
composition. Preferably at least 0.1% of them are used. Moreover, there is 
not usually used more than 5% by weight of salt of at least one metal 
chosen from lithium and/or the alkaline-earth metals with respect to the 
total weight of hydrofluoroalkanes contained in the composition. 
Preferably, 2% is not exceeded. 
Other stabilising agents and/or other additives can also be added to the 
hydrofluoroalkanes in the stabilised compositions according to the 
invention. 
The present invention also relates to compositions containing 
hydrofluoroalkanes, characterised in that they contain at least one salt 
of at least one metal chosen from lithium and/or the alkaline-earth metals 
in a sufficient quantity to stabilise the hydrofluoroalkanes contained in 
the composition. 
The nature of the stabilising salts and the quantities in which these (are 
advantageously used, as well as the nature of the compositions containing 
hydrofluoroalkanes, are those described above in the context of the 
process according to the invention. 
The compositions according to the invention can advantageously be used as 
blowing agents, as liquid coolants, as propellants or also as solvents. 
The compositions according to the invention can, in particular, consist of 
premixtures, containing hydrofluoroalkanes as blowing agents, intended for 
the preparation of foams, such as polyurethane foams. These compositions 
more particularly consist of polyol-based premixtures, containing 
hydrofluoroalkanes as blowing agents, intended for the manufacture of 
polyurethane foams. Excellent results have been obtained with compositions 
consisting of polyol-based premixtures, containing 
1,1-dichloro-1-fluoroethane as blowing agent, intended for the manufacture 
of polyurethane foams. Such compositions can also contain one or more 
other blowing agents. They have proven to be particularly stable in the 
presence of calcium chloride, giving rise, in particular, to only a very 
limited formation of 1-chloro-1-fluoroethane. 
The examples which follow are given, in a non-limiting way, in order to 
illustrate the invention. Example 1 is given as reference.

EXAMPLES 
Example 1R (reference) 
A premixture for the preparation of polyurethane foams is prepared 
according to the following composition, by weight: 
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50 aminated polyol ARCOL 3770 from Arco 
50 aminated polyol VORANOL RA 640 from Dow 
1 water 
2 silicone-containing surfactant B 1048 from 
Goldschmidt 
2 N-methylmorpholine 
1.5 N,N-dimethylcyclohexylamine 
24 1,1-dichloro-1-fluoroethane 
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A predetermined quantity of this mixture is confined in a glass flask 
maintained at a constant temperature of 50.degree. C. for 10 days. 
A sample is then withdrawn and its analysis by gas phase chromatography 
shows the presence of 256 mg of 1-chloro-1-fluoroethane per kg of 
1,1-dichloro-1-fluoroethane. 
Example 2 
There is added to a premixture identical to that of Example 1R, before 
ageing, 0.5% by weight of anhydrous calcium chloride with respect to the 
weight of 1,1-dichloro-1-fluoroethane. 
After ageing under conditions identical to those of Example 1R, only 29 mg 
of 1-chloro-1-fluoroethane per kg of 1,1-dichloro-1-fluoroethane are 
measured by gas phase chromatography. 
Example 3 
There are added to a premixture identical to that of Example 1R, before 
ageing, 5% by weight of anhydrous calcium chloride with respect to the 
weight of 1,1-dichloro-1-fluoroethane. 
After ageing under conditions identical to those of Example 1R, the 
quantity of 1-chloro-1-fluoroethane present is below the detection 
threshold by gas phase chromatography, which is 5 mg per kg of 
1,1-dichloro-1-fluoroethane. 
By comparison with reference Example 1R, Examples 2 and 3 show that the 
quantity of 1-chloro-1-fluoroethane formed is very markedly less and thus 
the stability of 1,1-dichloro-1-fluoroethane is very substantially 
improved in the presence of calcium chloride according to the invention.