Mixed Ester Refrigerator Oil for Lubrication and Startability

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Solution Overview

Problem

Refrigerant dissolution in refrigerating machine oil decreases the kinematic viscosity, leading to poor lubrication and potential seizure, while increasing the kinematic viscosity of the oil itself can cause it to remain in the evaporator tubes and reduce startability.

Innovation Solution

A mixed ester comprising polyol esters and complex esters, specifically esters of polyhydric alcohols, pentaerythritol, and dicarboxylic acids with mixed fatty acids, is used to increase refrigerant dissolution viscosity without excessively raising the kinematic viscosity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the kinematic viscosity of the refrigerating machine oil itself is increased to maintain lubrication when refrigerant dissolves, then the lubrication performance is improved, but the oil tends to remain in the evaporator or evaporator tube and startability decreases

Engineering Contradiction:

Improvelubrication performanceVSAvoidstartability

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The invention changes the chemical composition parameters of the base oil by using specific ester combinations (polyol ester, pentaerythritol ester, and complex ester) with controlled fatty acid ratios (iC4 acid 10-50 mol%, iC8 acid 30-80 mol%, iC9 acid 10-50 mol%). This chemical parameter optimization allows the oil to achieve the right balance between viscosity retention and flow characteristics, preventing oil accumulation in evaporators while maintaining adequate lubrication.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention uses a composite base oil formulation combining three different ester types (polyol ester, pentaerythritol ester, and complex ester) with specific fatty acid compositions. This composite approach leverages the complementary properties of each ester type to achieve both adequate viscosity for lubrication and appropriate flow characteristics to prevent evaporator accumulation, thereby resolving the contradiction between lubrication performance and startability.

Inventive Principle:

Principle #40Composite materials

2Ease of manufacture

If a simple ester composition is used, then the manufacturing process is simple, but the refrigerant dissolution viscosity is insufficient leading to poor lubrication

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoidlubrication performance

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The invention employs a composite ester composition consisting of three specific ester types (polyol ester, pentaerythritol ester, and complex ester) with defined fatty acid ratios. This composite structure provides synergistic effects that enhance refrigerant dissolution viscosity and lubrication performance beyond what any single ester could achieve, while still maintaining manufacturing feasibility through established esterification processes.

Inventive Principle:

Principle #40Composite materials

Data Source

PatentEP4640795A1Ester for refrigerator oil, base oil for refrigerator oil, refrigerator oil, and working fluid composition

Publication Date: 2025.10.29 ENEOS CORP

AI summary

An ester for refrigerating machine oil comprising: a first ester that is an ester of a polyhydric alcohol and a fatty acid having 6 to 9 carbon atoms; a second ester that is an ester of pentaerythritol and a fatty acid; and a third ester that is an ester of pentaerythritol, a dicarboxylic acid, and a fatty acid, wherein both the fatty acid constituting the second ester and the fatty acid constituting the third ester are mixed fatty acids comprising at least one selected from the group consisting of branched butanoic acid, branched pentanoic acid, and linear pentanoic acid, and either branched octanoic acid or branched nonanoic acid.