PURPOSE: To provide a highly viscous oil for refrigerators having a low pour point as well as excellent lubricity, sealing properties, chemical stability, thermal stability and low-temp. properties, which comprises an ester of a specific polypentaerythritol with a fatty acid (or its mixture).
CONSTITUTION: Pentaerythritol dispersed in a solvent is dehydrocondensed at about 180°C in the presence of a catalyst to obtain a polypentaerythritol having an average degree of polymerization of 1.2W6.5. The polypentaerythritol is esterified with 15wt% or more 8W18C branched satd. fatty acid (e.g.: isooctanoic acid) and a fatty acid mixture thereof with a 12W18C straight-chain satd. fatty acid (e.g.: lauric acid) in the presence of a strong acid catalyst (e.g.: P-toluenesulfonic acid), a metallic chloride catalyst (e.g.: SnCl2) or an alkoxy metal catalyst (e.g.: tetrabutoxysilane) to obtain a highly viscous oil for refrigerators having a pour point of -20°C or below and comprising polypentaerythritol.
MAEDA KAZUHITO
KOBASHI HITOSHI
KADOMA YOSHIHITO
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