Abstract (US 5928557):
This technology includes compositions of polymers that are useful as lubricants in heating and cooling compressor systems that use CFCs, HFCs and HCFCs as refrigerants. One key advantage is that the polymers are miscible with HFC refrigerants which are the desired replacements for environmentally damaging CFCs. By using more miscible and compatible lubricants the compressor efficiency is enhanced and the lifetime of heating and cooling systems can be extended.

Technology Benefits:
The diblock polymers are useful lubricants that are miscible or compatible with low-boiling, fluorine-containing halocarbons used as refrigerants, such as chlorofluorocarbons, hydrofluorocarbons, and hydrochlorofluorocarbons. However, it is preferable to use hydrofluorocarbons, an environmentally safer alternative to chlorofluorocarbons. Suitable hydrofluorocarbons include 1,1,1,2-tetrafluoroethane (HFC-134a), and 1,1,2,2-tetrafluoroethane (HFC-134). The lubricants are useful with the refrigerants for heating and cooling applications.
The diblock polymers may also be incorporated into lubricant compositions by covalent bonding to other chemical structures, for example, incorporated into a polymer backbone or appended to the polymer backbone. Further, the diblock polymer may be linked together in a repeating fashion, using various known synthetic approaches.
The diblock polymers may be blended with each other or with other lubricants, for example, perfluorocarbons, hydrofluorocarbons, fluorochlorocarbons, polyalkylene glycols, pentaerthyritol esters, other ester-based lubricants, naphthenic or paraffinic oils, alkylbenzenes, polyalkylbenzenes to modify viscosity, miscibility, and/or lubrication properties. For example, certain polyalkylene glycols, such as high molecular weight polypropylene glycol, may be immiscible in HFC-134a, although the lower molecular weight homologs are miscible. By blending the diblock polymers with these high molecular weight polymers a surprisingly large miscible temperature range is obtained. This feature provides important advantages when optimum miscibility and lubricity is desired within a required viscosity range.

Technology Uniqueness:
An advantage of this technology is maintenance of the chemical integrity and the desirable physical properties of the poly-a-olefin oligomer in the diblock polymer. Poly-a-olefins are excellent lubricants. However, if compatibilizing groups, that is groups that enable miscibility with refrigerants (such as fluoroalkene groups) were grafted to the hydrocarbon chain, such as described in U.S. Pat. No. 5,032,306, lubricant performance would be expected to suffer and the material cost would increase. It is known that properties of block copolymers can differ widely from random or graft copolymers or homopolymers of hybrid monomers. Surprisingly, the diblock polymers of the present invention retain the lubricity properties of the poly-a-olefins while the fluoroalkene oligomer facilitate miscibility with refrigerants.

Surprisingly, in addition to being useful as lubricants miscible with refrigerants, these diblock polymers have a remarkable ability to improve the miscibility of other lubricants known in the art, such as polyalkylene glycol, which in some cases are not sufficiently miscible in refrigerants due to chemical structure or molecular weight.
The temperature range for which a lubricant is miscible with the refrigerant is preferably -400 to 100° C. Generally, if the diblock polymer is miscible at low temperatures it will remain miscible at higher temperatures. However, this is not always true for some lubricants, which have immiscible regimes at both high and low temperatures. For any compositions, two critical solution temperatures, that is, lower and a higher temperature, may exist. That is, a relatively low temperature below which two distinct liquid phases are present and above which the two phases become miscible and a higher temperature at which the single phase disappears and two phases again may exist. Advantageously, these lubricants can extend the range of miscibility, that is, they tend to decrease the lower temperature and increase the higher temperature.

Intellectual Property Summary:
Patent No. US 5928557