The availability of refrigerants is impacted by an international treaty called the Montreal Protocol. The treaty is designed to protect the ozone layer by phasing out substances known to deplete it.
Under the treaty, early CFC refrigerants (like R-11) have been successfully phased out of use in most of the world. Newer HCFC refrigerants (like R-22) are on a phase out schedule that reduces how much R-22 can be imported each year.
No more R-22 will be imported into the US by the end of 2020.