Plasticizers are substances which, when added to another material, make that material softer and more flexible. Generally, this means that there is an increase in flexibility and workability, in some cases brought about by a decrease in the glass-transition temperature, Tg, of the polymer. The polymer to which a plasticizer is added is generally referred to as a “base polymer”. One base polymer that is commonly plasticized is poly(vinyl chloride) (PVC), and another polymer is poly(vinyl butyral) (PVB).
Commonly-used plasticizers include phthalates, including, for example, diisobutyl phthalate, dibutyl phthalate, and benylbutyl phthalate; adipates, including di-2-ethylhexyl adipate; trimellitates, including tris-2-ethylhexyl trimellitate; and phosphates, including tri-e-ethylhexyl phosphate. However, the use of some of these have been curtailed due to potential toxicity issues. Polyester plasticizers have also been used, but those have generally been based on condensation products of propanediol or butanediol with adipic acid or phthalic anhydride, and therefore may exhibit very high viscosities which subsequently cause processing problems in blending with other polymers. Plasticization of polymers is disclosed, for example, in D. F. Cadogan and C. J. Howick in Kirk-Othmer Encylclopedia of Chemical Technology, John Wiley and Sons, Inc., New York, Dec. 4, 2000, DOI:    10.1002/0471238961.1612011903010415.a01.
Various monocarboxylic acid mono- and diesters of polytrimethylene ether glycol have properties that make them useful in a variety of fields, including as lubricants. U.S. patent application Ser. No. 11/593,954 discloses the production of these esters and their use in a variety of functional fluids.
Epoxidized vegetable oils are also widely used plasticizers for PVC and other polymer matrices. These materials can provide low migration into adjoining materials, synergistic stabilizing and better low-temperature flexibility of the plasticized polymer material. Some of the epoxidized vegetable oils have been approved for use in food packaging applications. In the epoxidation process soybean oil and tall oil fatty acids used to react hydrogen peroxide and acetic acid in the presence of a catalyst and generates performic acid and other undesirable impurities. Generally, vegetable oils (as soybean oils, or refined grades of tall oil fatty acids) are a mixture of different saturated/unsaturated fatty acids; therefore, to manufacture esters with controlled structure and molecular weight is very difficult.
A need remains for processes and compositions for plasticizing polymers while minimizing impurities and improving properties of the polymers.