RU2844115C1 - Synthetic refrigerator oil - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to refrigerator oil which contains a polyol ester which is an ester of dipentaerythritol and a mixture of fatty acids. Fatty acids used are isononanoic and valeric acids in molar ratio (3.6÷4.4):(1.6÷2.4).

EFFECT: compatibility of the oil with fluorohydrocarbon and fluorocarbon refrigerants of the type R-134a, R-404a and analogues and compliance with the required parameters on kinematic viscosity, pour point, flash point, density, protective and lubricating properties.

1 cl, 2 tbl

Description

The invention relates to lubricating oils intended for piston compressors operating in refrigeration systems with ozone-sparing refrigerants.

Refrigeration oils based on polyol esters obtained by esterification of polyols with fatty acids are widely known.

A refrigeration oil is known that contains an ester of dipentaerythritol and an aliphatic acid in an amount of 20 mass% or more based on the total amount of the refrigeration oil, with a percentage of an aliphatic acid having 5 to 7 carbon atoms in the aliphatic acid constituting the ester of 20 mole% or more, and is used with a cooling liquid consisting of difluoromethane (JP 5919430 B2, 18.05.2016).

A refrigeration oil is known that contains the following components by volume: 28-76 parts of a first mixed solution of dipentaerythritol ether, 23-72 parts of a second mixed solution of dipentaerythritol ether, 0.8-1.2 parts of an antioxidant, 0.3-0.5 parts of an additive for lowering the pour point, 0.001-0.002 parts of a demulsifier, 0.002-0.005 parts of an antifoam, and 0.001-0.002 parts of an antiwear additive. The first mixed solution of dipentaerythritol ester is composed of dipentaerythritol, isononanoic acid, heptanoic acid and octanoic acid in equal volumes, and the second mixed solution of dipentaerythritol ester is composed of dipentaerythritol, isononanoic acid, pentanoic acid and heptanoic acid in successive corresponding volume ratios of 20-25/37-56/9-20/9-20. The refrigeration oil can meet the need for low pour point lubricant required in the field of HFC-404A refrigerant (CN 104152227 A, 2014-11-19).

The closest to the proposed refrigeration oil is a refrigeration oil that includes a base oil and an additive, wherein the base oil is a polyol ether, and the additive includes a thiophenol antioxidant (0.2-0.6%); the polyol ether is an ester of pentaerythritol and a mixture of fatty acids with a straight or branched chain C4-C9 or a mixed ester of dipentaerythritol and a mixture of fatty acids with a straight or branched chain C4-C9, in particular C5, C8 and C9; wherein the thiophenol antioxidant contains two phenolic hydroxyl groups -OH and two -S-sulfur bonds. The oil also contains an anti-wear phosphorus-containing additive, including tricresyl phosphate (0.1-2%), an acid scavenger selected from glycidyl ethers (0.1-2%), a corrosion inhibitor - benzotriazole or its derivatives. The oil can be used in a refrigeration machine with hydrofluorocarbon refrigerant (CN 112251272 A2, 22.01.2022). This technical solution is adopted as a prototype.

The technical problem solved by the invention consists in expanding the range of synthetic lubricating oils for piston compressors of refrigeration systems.

The technical result achieved by the invention consists in ensuring compatibility of oil with fluorocarbon and fluorocarbon freons of the R-134a, R-404a and analogues type and compliance with the required parameters for kinematic viscosity, pour point, flash point, density, protective and lubricating properties.

The technical result is achieved by a refrigeration oil containing a polyol ester, which is an ester of dipentaerythritol and a mixture of fatty acids, which, according to the invention, includes isononanoic and valeric acids as fatty acids in a molar ratio of (3.6÷4.4):(1.6÷2.4).

Synthetic polyol ester – refrigeration oil was obtained by esterification of dipentaerythritol (hexahydric alcohol) with a mixture of isononanoic and valeric acids in a molar ratio of (3.6÷4.4):(1.6÷2.4). The molar ratio of the alcohol and acids participating in the reaction is 1 to 6, respectively.

Table 1 presents examples of the compositions of the proposed refrigeration oil – dipentaerythritol ester.

Table 1

Name of components Polyol Ether Compositions 1 2 3 Molar ratio of dipentaerythritol and acids 1:6 1:6 1:6 Molar ratio of isononanoic and valeric acids 3.6:2.4 4.0:2.0 4.4:1.6

The polyol ester is obtained as follows:

The reactor, an enameled heated apparatus, is loaded with raw materials - dipentaerythritol, isononanoic and valerianic acids in the above proportions, and the reaction mass is heated to a temperature of 200-250°C. When the set temperature is reached, stirring is carried out for 10-18 hours. Throughout the process, water formed as a result of the interaction of polyol and fatty acids is removed.

Upon completion of the main process, unreacted components are removed at a temperature of 220-270°C.

Table 2 presents the refrigeration oil properties for the compositions presented in Table 1.

Table 2

Name
indicator Norm Typical indicators Method
tests composition 1 composition 2 composition 3 1. Appearance Clear liquid from transparent to light yellow color Clear transparent light liquid Visually 2. Density at 20°C, g/ ^cm3 , within 0.940-0.999 0.983 0.981 0.979 GOST 3900
ISO 12185 3. Kinematic viscosity, ^mm2 /s,
- at 40°C, within 167-183 167.5 175.4 182.1 GOST 33
ISO 3104 4. Viscosity index, not less than 100 101 102 104 GOST 25371
ISO 2909 5. Flash point, determined in an open crucible, °C, not lower 230 277 279 282 GOST 4333
ISO 2592 6. Acid number,
mg KOH/g, no more than 0.05 0,015 0,018 0.022 GOST 5985
ISO 6618 7. Mass fraction of water, %, no more than absence absence GOST 2477 8. Mass fraction of mechanical impurities, %, no more than absence absence GOST 6370 9. Content of water-soluble acids and alkalis absence absence GOST 6307

The proposed refrigeration oil meets all the requirements and has shown good compatibility with freons of the R-134a and R-404a types and analogues.

Refrigeration oil is safe for humans when it comes into contact with the skin, mucous membranes and when it enters the digestive system.

Claims (1)

Refrigeration oil containing a polyol ester, which is an ester of dipentaerythritol and a mixture of fatty acids, characterized in that it includes isononanoic and valeric acids as fatty acids in a molar ratio of (3.6÷4.4):(1.6÷2.4).