JP6043831B2 - How to lubricate a rotary screw compressor - Google Patents

Description

  The present invention mainly relates to a lubricating oil for use in a rotary screw compressor that utilizes an ester-based lubricating oil, particularly a hydrofluorocarbon (HFC) containing no chlorine as a refrigerant.

  Heating, refrigeration or air conditioning systems that typically use a rotary screw compressor are commonly found in office buildings, hotels, shopping malls, food storage and processing equipment, chemical processing, a wide variety of manufacturing plants, and the like. Keeping operating costs low is an important task for building owners as well as manufacturing plant managers. In this regard, the ability to keep heating and cooling costs low is important; ASHRAE (American Society of Heating, Refrigeration and Air-Conditioning Engineers) is caused by heating or cooling for 50% of the building's energy consumption It is estimated that. Moreover, if energy efficiency can be improved, there are significant positive environmental and social effects.

  A rotary screw compressor is a type of positive displacement compressor. An important part of a conventional rotary screw compressor consists of two meshing parallel helically contoured rotors housed in a casing. The movement and design of the rotor allows the gas to be drawn in, sealed and compressed by moving the gas from its inlet to its outlet. In the design of a rotary screw compressor filled with oil, the lubricating oil fills the gaps between the rotors, thus providing a hydraulic seal and transferring mechanical energy between the drive motor and the driven motor.

  The fundamental requirements for a rotary screw compressor are robustness and reliability. This is because the rotary screw compressor is expected to have a service life of several years or decades, and during that time, it is expected to operate continuously with little maintenance work. The robustness and energy efficiency of rotary screw compressors has been achieved, and in order to better seal the compression cavities, mechanical engineers have made accurate fittings and tight clearances between the helical rotors and between the rotor and chamber. We are continuously pursuing accurate assembly by applying advanced digital materials and modern digital controllers with intelligent algorithms. However, lubricants can be a relatively cost effective way to achieve higher efficiency. The optimal result appears to be a lubricant that improves both the efficiency and reliability of the compressor.

  The evaporator is an important component in a cooling or air conditioning system; it is in the evaporator that the actual cooling or heat exchange takes place. An evaporator is a kind of heat exchanger that transfers heat between substances. In the case of an air conditioner, the substance is between a refrigerant and air cooled by the refrigerant. A common requirement for evaporators is that the heat transfer surface, whether inside or outside the evaporator, must be cleaned so as not to impede heat transfer by conduction. For example, defrosting is commonly used for this purpose. The effect on the heat transfer of the lubricating oil is due to the fact that the lubricating oil is pumped out of the outlet along with the exhaust gas. Many refrigeration systems or chillers typically have oil separators made downstream from the outlet, but these oil separators cannot capture all the lubricating oil molecules. It is inevitable that some lubricating oil will pass through the separator. The passing lubricating oil needs to be drawn back to the compressor; otherwise, the accumulation of lubricating oil in the area outside the compressor causes an oil bleed condition inside the compressor and / or May interfere with system functionality, such as heat transfer in cooling or air conditioning system evaporators. Lubricants that are designed to be compatible / miscible with the refrigerant, can circulate back to the compressor with the refrigerant, and have little tendency to accumulate on the evaporator surface are highly desirable.

  While having excellent compatibility / miscibility with refrigerants, lubricating oils capable of providing better hydraulic sealing have conflicting requirements. For example, high viscosity lubricants generally provide more effective hydraulic sealing and anti-wear properties, but they tend not to be particularly compatible or miscible with lower temperature refrigerants. . A serious inverse implication of this inadequate compatibility / miscibility is inadequate oil return and reduced heat transfer in the area of the low temperature evaporator / heat exchanger.

  The challenge in developing high viscosity, improved performance lubricants is further complicated by the adoption of environmentally friendly hydrofluorocarbon (HFC) refrigerants that do not deplete ozone. Conventional chlorofluorocarbon (CFC) or hydrochlorofluorocarbon (HCFC) refrigerants are inherently slightly polar due to the presence of chlorine atoms and are therefore usually good solvents. Hydrofluorocarbon (HFC) refrigerants that do not contain chlorine atoms are inferior solvents, thus making it more difficult to find compatible / miscible lubricants for high viscosity lubricants.

  In addition to finding lubricants that can provide better hydraulic sealing, anti-wear properties and better compatibility / miscibility to increase compressor system efficiency, these innovative lubricants Suitable hydrodynamic lubrication film thickness, high dielectric strength, excellent hydrolytic stability, good thermal stability, high flash point, low pour point, and high viscosity index (VI), etc. It is indispensable to maintain the properties that conventional cooling machine lubricants generally have.

  The main object of the present invention is a method of lubricating a rotary screw compressor in which a chlorine-free hydrofluorocarbon refrigerant is compressed, wherein the lubricant composition of the present invention is mixed with a chlorine-free hydrofluorocarbon refrigerant. Is to provide a method that includes:

  Another object of the present invention is to provide a lubricant composition and a refrigerant working fluid to improve the performance of a rotary screw compressor, such refrigerant working fluid being a lubricant of the present invention. And a hydrofluorocarbon refrigerant that does not contain chlorine.

  Still another object of the present invention is to provide a rotary screw compressor including the refrigerant working fluid of the present invention.

  It is a further object of the present invention to provide a cooling device, or heat pump system or air conditioner that includes the rotary screw compressor of the present invention.

  To achieve the above objective, the lubricant composition provided according to the present invention comprises a mixed polyester of formula (I) or (II):

In the above formula, each of R ^{1 to} R ⁸ is a carboxylate of a C5-C10 monocarboxylic acid, and the mixed polyester has two or more different carboxylates of a C5-C10 monocarboxylic acid.

Preferred embodiments of the present invention include (but are not limited to) the features listed in the following items:
1. Lubricating a rotary screw compressor in which a chlorine-free hydrofluorocarbon refrigerant is compressed (wherein the chlorine-free hydrofluorocarbon refrigerant is preferably R-134a, R-32, R-125 or a mixture thereof) A method,
Mixing a lubricant composition with the chlorine-free hydrofluorocarbon refrigerant,
The lubricant composition has the formula (I) or (II):

Wherein each of R ^{1 to} R ⁸ is a carboxylate of a C5-C10 monocarboxylic acid,
Wherein the mixed polyester has two or more different carboxylates of the C5-C10 monocarboxylic acid.

2. The mixed polyester is represented by the formula (I), the C5-C10 monocarboxylic acid includes a C5 carboxylic acid and a C9 carboxylic acid or a C10 carboxylic acid, and the carboxylate of R ^{1 to} R ⁵ is Item 2. The method of item 1, wherein the method has a ratio of 6: 1 to 1: 4 between the weight of the C5 carboxylic acid and the total weight of the C9 and C10 carboxylic acids.

  3. Item 3. The item 5, wherein the C5 carboxylic acid includes n-pentanoic acid or methylbutanoic acid, the C9 carboxylic acid includes 3,5,5-trimethylhexanoic acid, and the C10 carboxylic acid includes neodecanoic acid. Method.

  4). The carboxylate of n-pentanoic acid, methylbutanoic acid and 3,5,5-trimethylhexanoic acid, wherein the mixed polyester is in a weight ratio of about 1-3: 6-8: 2, preferably about 2: 7: 2. The method according to item 3, comprising:

  5. The mixed polyester is a reaction of tripentaerythritol with a mixed carboxylic acid composed of n-pentanoic acid, methylbutanoic acid and 3,5,5-trimethylhexanoic acid, or tripentaerythritol, n-pentanoic acid and methylbutanoic acid And a molar ratio of hydroxyl groups to carboxyl groups of about 1.0: 1.02 to 1.2, obtained from a reaction with 1, 2 or 3 carboxylic acids selected from 3,5,5-trimethylhexanoic acid. Preferably, the mixed polyester is a product mixture obtained from the reaction of tripentaerythritol with a mixed carboxylic acid consisting of n-pentanoic acid, methylbutanoic acid and 3,5,5-trimethylhexanoic acid. Item 5. The method according to Item 4.

6). The lubricant composition includes the mixed polyester represented by the formula (I) and the mixed polyester represented by the formula (II), and each of R ^{6 to} R ⁸ is a C5 monocarboxylic acid, preferably methylbutane. It is a carboxylate of an acid, and the weight ratio of the mixed polyester represented by the formula (I) and the mixed polyester represented by the formula (II) is 7: 3 to 1: 2, preferably about 1: 1. The method according to item 1, wherein

7). The C5-C10 monocarboxylic acid includes a C5 carboxylic acid and a C9 carboxylic acid or a C10 carboxylic acid, and the carboxylate of R ^{1 to} R ⁵ includes the weight of the C5 carboxylic acid, the C9 carboxylic acid, and the C10. Item 7. The method according to Item 6, having a ratio of 6: 1 to 1: 4 with respect to the total weight of the carboxylic acid.

  8). The C5-C10 monocarboxylic acid includes methylbutanoic acid and 3,5,5-trimethylhexanoic acid, and the ratio of the weight of 3-methylbutanoic acid to the weight of 3,5,5-trimethylhexanoic acid is about Item 8. The method according to Item 7, which is 3: 7.

  9. Item 8. The method according to Item 7, wherein the C5-C10 monocarboxylic acid comprises methylbutanoic acid and neodecanoic acid, and the ratio of the weight of methylbutanoic acid to the weight of neodecanoic acid is about 1: 3.

  10. The mixed polyester has the formula (II), the C5-C10 monocarboxylic acid includes a C5 carboxylic acid and a C9 carboxylic acid, and the carboxylate of R6 to R8 has a weight ratio of 5: 1 to 1. A process according to item 1, having a weight of the C5 carboxylic acid and a C9 carboxylic acid of: 4, preferably 2: 1 to 1: 2, more preferably about 1: 1.

  11. The C5 carboxylic acid includes methylbutanoic acid, the C9 carboxylic acid includes 3,5,5-trimethylhexanoic acid, and the mixed polyester represented by the formula (II) includes dipentaerythritol, methylbutanoic acid, and Item 10, a product mixture obtained from the reaction of 3,5,5-trimethylhexanoic acid with a mixed carboxylic acid, wherein the molar ratio of hydroxyl groups to carboxyl groups is about 1.0: 1.05 to 1.2. The method described in 1.

  12 Item 2. The method of item 1, wherein the lubricant composition has a viscosity of 160 to 460 centistokes at 40 ° C, preferably 220 to 360 centistokes at 40 ° C.

  13. The chlorine-free hydrofluorocarbon refrigerant is R-134a, and in the hydrofluorocarbon refrigerant not containing chlorine, the lubricant composition is the lubricant composition and the chlorine-free hydrofluorocarbon. A temperature lower than −35 ° C., preferably lower than −45 ° C., more preferably lower than −60 ° C. when included at 5 wt%, 10 wt% and 20 wt% relative to the total weight of the refrigerant. 13. The method of item 12, wherein the lubricant composition is miscible with the chlorine-free hydrofluorocarbon refrigerant.

  14 The method of item 1, wherein another lubricant or base stock composition is blended with the lubricant composition in a ratio of less than 20% based on the weight of the lubricant composition.

  15. Oxidation resistance and thermal stability improver, corrosion inhibitor, metal deactivator, lubricity imparting agent, viscosity index improver, pour point and / or flock point depressant, detergent, dispersant, defoamer, acid scavenger One or more additives selected from the group consisting of an agent, an antiwear agent, and an extreme pressure resistor are the lubricant composition, the chlorine-free hydrofluorocarbon or the lubricant composition and the chlorine-free hydro A method according to item 1, wherein the mixture is mixed with a mixture of fluorocarbons in an amount of 3% or less than 3% based on the weight of the mixture.

  The present invention discloses an ester-based lubricating oil and a refrigerant working fluid for a rotary screw compressor containing the ester-based lubricating oil and a chlorine-free hydrofluorocarbon refrigerant. The working fluid of the present invention is capable of improving the performance / efficiency of a rotary screw compressor, which in turn improves the performance / efficiency of a cooling device, heat pump system or air conditioner that includes the rotary screw compressor.

  An ester-based synthetic lubricating oil comprises dipentaerythritol (DiPE), tripentaerythritol (TriPE) or a mixture thereof in the presence or absence of a catalyst, and a mixed monocarboxylic acid having a chain length of 5 to 10 carbon atoms. Contains the esterification product, followed by purification. In order to improve the efficiency or yield of chemical synthesis, an excess of acid is used to react with one or more polyols. Typical reaction temperatures range from 150 to 250 ° C. (preferably 180 to 240 ° C., more preferably 200 to 230 ° C.), and typical reaction times range from 6 hours to 18 hours (preferably from 8 hours to 14 hours, more preferably 8 hours to 12 hours). Typical catalysts that can be used in esterification include (but are not limited to) stannous oxalate, stannous oxide, tetra-n-butyl titanate, tetraisopropyl titanate, and methanesulfonic acid. Can be mentioned. The esterification product generally has a hydroxyl number lower than 10 mg KOH / g (preferably lower than 5 mg KOH / g, more preferably lower than 3 mg KOH / g). The purification process generally involves removing water by vacuum, removing acid by neutralization with NaOH, and discoloration by carbon black absorption. The final purified polyester product has a total acid number (TAN) of less than 0.1 mg KOH / g and a water content of less than 50 ppm. Low water content is achieved by bubbling dry nitrogen into the purified polyester product.

  DiPE and TriPE may be purified or have a certain amount of polyol commonly found in commercially available DiPE or TriPE. Monocarboxylic acids, in particular C5 monocarboxylic acids and C9 monocarboxylic acids, may be linear or branched. C5 monocarboxylic acids preferably include (but are not limited to) 2-methylbutanoic acid, 3-methylbutanoic acid, and mixtures thereof; C9 monocarboxylic acids are preferably 3, 5, 5 -Trimethylhexanoic acid.

  Under some conditions of use, the ester (s) described herein will function well as a complete lubricant. However, complete lubricants include other materials commonly recognized in the industry as additives, such as oxidation resistance and thermal stability improvers, corrosion inhibitors, metal deactivators, lubricity enhancers, viscosity index It is usually preferred to contain improvers, pour and / or flock point depressants, detergents, dispersants, antifoaming agents, acid scavengers, antiwear agents, extreme pressure resistors and the like. Many additives are multifunctional. For example, certain additives can provide both antiwear and extreme pressure resistance, or can function as both metal deactivators and corrosion inhibitors. Cumulatively, all additives preferably do not exceed 8%, more preferably not exceed 5% by weight of the total formulated lubricant formulation.

  Effective amounts of the aforementioned additive types are typically 0.01-5% for the antioxidant component, 0.01-5% for the corrosion inhibitor component, and 0.001-0 for the metal deactivator component. 0.5% for lubricant imparting agents, 0.5-5% for acid scavengers, viscosity index improvers, and 0.01-2% for each of pour and / or flock point depressants, detergents and dispersants It is in the range of 0.1 to 5% for each, 0.001 to 0.1% for the antifoaming agent, and 0.1 to 2% for each of the antiwear and extreme pressure resistant components. All of these percentages are by weight and are based on the total lubricant composition. Less or more than the amount of additive mentioned may be more suitable for a particular environment, and a single molecular species or mixture of species is used for each type of additive component It will be understood that this may be done. Also, except as set forth in the appended claims, the examples listed below are merely illustrative and not limiting.

  Suitable oxidation resistance and thermal stability improvers are diphenyl-, dinaphthyl-, and phenylnaphthyl-amine, where the phenyl and naphthyl groups can be substituted, for example, N, N'- Diphenylphenylenediamine, p-octyldiphenylamine, p, p-dioctyldiphenylamine, N-phenyl-1-naphthylamine, N-phenyl-2-naphthylamine, N- (p-dodecyl) phenyl-2-naphthylamine, di-1-naphthylamine And di-2-naphthylamine; phenothiazines such as N-alkylphenothiazines; imino (bisbenzyl); and hindered phenols such as 6- (t-butyl) phenol, 2,6-di- (t-butyl) phenol, 4-methyl-2,6-di- (t- Chill) phenol, 4,4'-methylenebis (2,6-di - {t-butyl} phenol), and those like can be exemplified.

  Examples of suitable cuprous metal deactivators include imidazole, benzimidazole, 2-mercaptobenzothiazole, 2,5-dimercaptothiadiazole, salicylidene-propylenediamine, pyrazole, benzotriazole, toltriazole, 2-methylbenzimidazole, 3,5-dimethylpyrazole, and methylenebis-benzotriazole. Benzotriazole derivatives are preferred. Other examples of more common metal deactivators and / or corrosion inhibitors include organic acids and their esters, metal salts, and anhydrides such as N-oleyl-sarcosine, sorbitan monooleate, naphthenes Lead acid, dodecenyl-succinic acid and its partial esters and amides, and 4-nonylphenoxyacetic acid; primary and secondary, and tertiary aliphatic and alicyclic amines and amine salts of organic and inorganic acids, such as , Oil-soluble alkylammonium carboxylates; heterocyclic nitrogen-containing compounds such as thiadiazole, substituted imidazolines, and oxazolines; quinoline, quinone, and anthraquinone; propyl gallate; barium dinonylnaphthalene sulfonate; alkenyl succinic anhydride Acid spa And amide derivatives, dithiocarbamates, dithiophosphates; include amine salts and their derivatives of the acid phosphoric acid ester.

  Examples of suitable lubricity-imparting agents include long chain derivatives of fatty acids and natural oils such as esters, amines, amides, imidazolines, and borates.

  Examples of suitable viscosity index improvers include polymethacrylates, vinylpyrrolidone and methacrylate copolymers, polybutenes, and styrene-acrylate copolymers.

  Examples of suitable pour point and / or floc point depressants include polymethacrylates such as methacrylate-ethylene-vinyl acetate terpolymers; alkylated naphthalene derivatives; and Friedel-Crafts catalyzed condensation of urea with naphthalene or phenol. Products.

  Examples of suitable detergents and / or dispersants include polybutenyl succinic acid amides; polybutenyl phosphonic acid derivatives; long chain alkyl-substituted aromatic sulfonic acids and their salts; and metal salts of alkyl sulfides, metals of alkyl phenols Salts, and metal salts of condensation products of alkylphenols and aldehydes.

  Examples of suitable antifoaming agents include silicone polymers and some acrylates. Examples of suitable acid scavengers are glycidyl ethers and esters.

  Examples of suitable antiwear and extreme pressure resistance agents include sulfurized fatty acids and fatty acid esters, such as sulfurized octyl tartrate; sulfurized terpenes; sulfurized olefins; organic polysulfides; , Dialkyl phosphates, amine dithiophosphates, trialkyl and triaryl phosphorothioates, trialkyl and triaryl phosphines, and dialkyl phosphites such as amine salts of monohexyl phosphate, amine salts of dinonylnaphthalene sulfonate, tri Phenyl phosphate, trinaphthyl phosphate, diphenyl cresyl and dicresyl phenyl phosphate, naphthyl diphenyl phosphate, triphenyl phosphorothio Organic phosphorus derivatives including nates; dithiocarbamates such as antimony dialkyldithiocarbamates; chlorinated and / or fluorinated hydrocarbons; and xanthates.

  The invention will be better understood by the following examples which are merely to illustrate the invention and not to limit the scope of the invention. In the following examples, 2-methylbutanoic acid (MBA) was used; however, MBA can be replaced with 3-methylbutanoic acid or a mixture of 2-methylbutanoic acid and 3-methylbutanoic acid. Thus, methylbutanoic acid in the claims means 2-methylbutanoic acid, 3-methylbutanoic acid or a mixture of 2-methylbutanoic acid and 3-methylbutanoic acid.

Example 1. TriPE + (iC9, MBA, nC5)
In this example, mixed polyol ester (POE) is converted into TriPE (tripentaerythritol), 3,5,5-trimethylhexanoic acid (iC9 acid), 2-methylbutanoic acid (MBA) and n-pentanoic acid (nC5 acid). ) In a 2: 7: 2 weight ratio mixture.

  The POE synthesis procedure described in this example was also employed in the following examples, changing the reactants and their amounts. For example, Jiangsu Ruiyang Chemical Co. in China. , Ltd., Ltd. TriPE sold by Dow Chemical, for example, carboxylic acid, nC5 acid sold by Dow Chemical; for example MBA sold by Oxea Corporation of the United States; and iC9 acid sold by KH Neochem, Japan, for example, Was placed in a 1 liter flask equipped with a nitrogen purge tube and a stirrer and placed in a temperature controlled heating mantle. An excess stoichiometric amount of acid was used in the reaction; the ratio of hydroxyl groups in the alcohol to carboxyl groups in the mixed carboxylic acid was from 1: 1.1 to 1.2. The reaction between alcohol and acid was promoted by stirring and heating at 200 ° C. to 230 ° C. under a nitrogen atmosphere. During the reaction, water generated was removed by distillation and the hydroxyl number of the reaction mixture was monitored. When the hydroxyl number was below 3 mg KOH / g, the reaction was stopped by discontinuing heating and stirring, which took about 8-12 hours. The product mixture was further purified by removing water by vacuum, acid removal by neutralization with NaOH, and discoloration by carbon black absorption. Thereafter, nitrogen was bubbled at a temperature controlled to 50 ° C. to 100 ° C. to dehydrate the purified ester. The final polyester product has a total acid number (TAN) of less than 0.1 mg KOH / g and a water content of less than 50 ppm.

  The POE prepared in this example is not only high viscosity, which is a contradictory requirement, but also an HFC refrigerant such as R-134a (1,1,1,2-tetrafluoroethane, which is To achieve high miscibility with the The POE of Example 1 has the following physical properties.

Example 2 TriPE + (MBA, iC9) and DiPE + MBA blend (50/50)
The innovative POE prepared in this example has a viscosity of ISO 220 at 40 ° C., a weight ratio of 50:50, a polyester derived from TriPE + (MBA and iC9 acid in a weight ratio of 30:70), It is composed of polyester derived from DiPE + MBA. This mixed POE oil can be made by blending two separately made POEs or by reacting TriPE and DiPE with MBA and iC9 acid under controlled conditions. In this example, the mixed POE oil was produced by mixing two POEs prepared separately as in Example 1. The mixed POE prepared in this example has the following physical properties:

Example 3 DiPE + MBA and TriPE + (Neo 10 + MBA) blend (45/55)
The innovative POE prepared in this example has a viscosity of ISO 400 at 40 ° C., a weight ratio of 45:55, DiPE + MBA, and TriPE + (neodecanoic acid (neo 10) + MBA, weight ratio 3: 1). And a blend.

  In this example, the mixed POE oil was produced by blending two separately prepared POEs as in Example 1. Even at a very high viscosity of 400 cSt at 40 ° C., the POE produced in this example surprisingly has high miscibility with HFC refrigerants such as R-134a, as shown in Example 4. Was found. This POE has the following physical properties:

Example 4 Comparison of miscibility A comparison of the compatibility / miscibility of the R-134a refrigerant between the lubricating oils prepared in Examples 1, 2 and 3 and a conventional POE lubricating oil is shown in this example. Two commonly used commercial POE lubricants—ISO 68 and ISO 120 POE lubricants—was chosen for comparison.

  The phase separation temperature measured at low temperature is used to indicate the compatibility / miscibility. Taking an oil concentration of 20% as an example in the refrigerant, 0.6 g of sample oil and 2.4 g of refrigerant R-134a are placed in a thick PYREX® tube (total length 300 mm, outer diameter 10 mm, and inner diameter 6 mm). And cooled in an ethanol bath containing dry ice and warmed. Next, the two-phase separation temperature was measured visually within the temperature range of + 60 ° C to -60 ° C. The results are shown in Table 1.

  POE lubricants tend to be more compatible / miscible with R-134a refrigerant as the viscosity is lower (although not necessarily). However, the lubricating oils prepared in Examples 1, 2 and 3 show much better miscibility / compatibility at oil concentrations of 5%, 10% and 20% in the refrigerant. This compatibility / miscibility facilitates oil return from the evaporator or piping in the cooling or air conditioning system.

Example 5 FIG. Critical Cool Lubricity-Water Specification, Total Acid Number (TAN) and Dielectric Strength Measurements To meet the requirements of closed loop cooling, air conditioning or heating systems, compressor lubricants have been recognized by industry It is necessary to meet quality standards. Important among them are water composition, total acid number (TAN) and dielectric strength. Since water reacts with esters to form acids, the water content of the POE lubricating oil should be minimal. Moreover, excess water in the oil can freeze on the metal surface and hinder heat transfer. The total acid number (TAN) in the POE lubricating oil should also be minimal because the acid not only causes corrosion but can also catalyze the decomposition of the ester. Dielectric constant is important because POE lubricant is in frequent contact with electrical components such as system motors. If the dielectric constant is low (high conductivity), the probability of a short circuit will increase. In the following table (Table 2), these properties of the POEs prepared in Examples 1, 2 and 3 are shown, and the POEs prepared in accordance with the present invention meet stringent lubricant requirements in cooling, air conditioning and heating systems. Can be seen from the data in the table.

Example 6 Sealed tube stability test Lubricant stability in cooling, air conditioning or heating systems is important because the decomposed product can clog the filter and cause corrosion or wear problems. In addition, problems due to the decomposition of the lubricant will be exacerbated by the closed loop circulation design. One of the main differences between lubricants used in closed loop cooling, air conditioning and heating systems and lubricants used in engine or gear applications is used in closed loop cooling, air conditioning and heating systems Lubricating oil is to operate in a refrigerant environment instead of the normal atmospheric environment. Thus, for example, to evaluate the stability of a POE lubricant used with R-134a, it is only meaningful to perform the test in an R-134a environment, and therefore a sealed tube test is employed.

  Lubricants that fail to pass the sealed tube stability test may form acids, deposits, insoluble materials, which lead to corrosion, valve sticking, filter clogging, capillary tube clogging or viscosity changes Sometimes. All of these can result in excessive energy consumption, poor system performance and / or expensive maintenance operations.

  Table 3 shows the results of the sealed tube test of the lubricating oil prepared in Examples 1, 2, and 3. The data in Table 3 shows that the lubricating oil of the present invention is stable in the refrigerant environment based on industry standard tests. These results show that the lubricating oil of the present invention works long and without problems when the cooling, air conditioning or heating system is properly assembled.

Example 7 Comparison of compatibility / miscibility between the lubricating oil prepared in Example 2 and two conventional POE lubricating oils having the same viscosity grade in R-134a Same compatibility used in Example 4 The miscibility test was repeated separately for the two conventional ISO 220 POE lubricants (RB220 and RL220) and the lubricant prepared in Example 2. The results are shown in Table 4. In the table, RB220 of the two conventional ISO 220 POE lubricants is composed primarily of branched acid-derived polyesters, while RL220 is more linear. The lubricating oil prepared in Example 2 is also ISO 220 grade. The data in Table 4 clearly shows the miscibility differences between the two conventional ISO 220 POE lubricants and the lubricant prepared in Example 2. The surprisingly high miscibility of the lubricant prepared in Example 2 will result in a cleaner metal surface in a closed loop system and thus less heat transfer compared to conventional POE cooled lubricants. Provides impedance.

Example 8 FIG. Hydrolysis stability test (ASTM 2619)
Closed loop cooling, air conditioning and heating systems should be assembled with great care to minimize contamination and water contamination. In addition, these systems generally employ a filter / dryer to absorb water as an additional safety design. However, it is difficult to seek perfection in all cases because there are a large number of systems currently in use or built in the future, and the contractor's skills are not consistent. . As a result, water may inevitably enter some of these closed loop systems. Therefore, as a result, it is always preferable that the lubricating oil has a high level of hydrolysis resistance. A commonly used hydrolysis stability test is ASTM 2619, where water and oil are placed together under mechanical mixing at elevated temperatures for extended periods of time. Lubricating oils that are susceptible to hydrolysis can form acids (insoluble) or suffer a loss of viscosity. Table 5 shows the test results for the lubricating oils prepared in Examples 1, 2, and 3.

  From Table 5, it can be clearly seen that the POE lubricating oils prepared in Examples 1, 2 and 3 demonstrate sufficient hydrolytic stability in the ASTM 2619 test. These can be said to be a result of providing further reliability even when the POE lubricating oil of the present invention is used on a large scale.

Example 9 DiPE + (iC9, MBA)
In this example, by reacting DiPE (dipentaerythritol) with a 1: 1 weight ratio mixture of 3,5,5-trimethylhexanoic acid (iC9 acid) and 2-methylbutanoic acid (MBA). A mixed polyol ester (POE) was synthesized.

  The same synthetic procedure described in Example 1 was applied to this example by making the necessary changes in the reactants and their amounts. DiPE, MBA and iC9 acid were placed in a 1 liter flask equipped with a thermometer, nitrogen purge tube, and stirrer, which was placed in a temperature controlled heating mantle to initiate the synthesis reaction. Similarly; finally, the product mixture was further purified by water removal by vacuum, acid removal by neutralization with NaOH, and discoloration by carbon black absorption. Then, nitrogen bubbling was performed at a temperature controlled to 50 ° C. to 100 ° C. to dehydrate the purified ester. The final polyester product has a total acid number (TAN) of less than 0.1 mg KOH / g and a water content of less than 50 ppm.

  The POE prepared in this example not only has high viscosity, which is a contradictory requirement, but also realizes high miscibility with HFC refrigerants such as R-134a. The POE obtained in this example has the following physical properties.

  The miscibility of the HFC refrigerant into R-134a etc. of the POE prepared in this example is shown as follows:

Claims (12)

A method of lubricating a rotary screw compressor, wherein a chlorine-free hydrofluorocarbon refrigerant is compressed,
Mixing a lubricant composition with the chlorine-free hydrofluorocarbon refrigerant,
The base oil of the lubricant composition is a mixed polyester represented by the formula (I), or a mixed polyester represented by the formula (I) and a mixed polyester represented by the formula (II):
Wherein each of R ^{1 to} R ⁸ is a carboxylate of a C5-C10 monocarboxylic acid,
Consists of
The mixed polyester represented by the formula (I) has two or more different carboxylates of the C5-C10 monocarboxylic acid,
The C5-C10 monocarboxylic acids consists of a C5 carboxylic acid, a C9 carboxylic acid or C10 carboxylic acids,
The carboxylate R ¹ to R ⁵ is, and weight of the C5 carboxylic acids, between the total weight of the C9 acid and C10 acids, 6: 1 to 1: have a ratio of 4,
When the lubricant composition includes the mixed polyester represented by the formula (I) and the mixed polyester represented by the formula (II),
Each of R ^{6 to} R ⁸ is a carboxylate of a C5 monocarboxylic acid;
A method in which a weight ratio between the mixed polyester represented by the formula (I) and the mixed polyester represented by the formula (II) is 7: 3 to 1: 2 . The C5 carboxylic acid comprises n-pentanoic acid or methylbutanoic acid,
The C9 carboxylic acid comprises 3,5,5-trimethylhexanoic acid;
The method of claim 1, wherein the C10 carboxylic acid comprises neodecanoic acid.   The mixed polyester represented by the formula (I) has the carboxylate of n-pentanoic acid, methylbutanoic acid and 3,5,5-trimethylhexanoic acid in a weight ratio of 1 to 3: 6 to 8: 2. The method of claim 2.   The mixed polyester represented by the formula (I) is a reaction of tripentaerythritol with a mixed carboxylic acid composed of n-pentanoic acid, methylbutanoic acid and 3,5,5-trimethylhexanoic acid, or tripentaerythritol, Obtained from the reaction with 1, 2 or 3 carboxylic acids selected from n-pentanoic acid, methylbutanoic acid and 3,5,5-trimethylhexanoic acid, the molar ratio of carboxyl groups to hydroxyl groups is 1.02-1 The process of claim 3, wherein the product mixture is .2: 1.0.   The mixed polyester represented by the formula (I) is a product mixture obtained from a reaction of tripentaerythritol with a mixed carboxylic acid composed of n-pentanoic acid, methylbutanoic acid and 3,5,5-trimethylhexanoic acid. The method of claim 4. The method of claim 1 , wherein each of R ^{6 to} R ⁸ is a methylbutanoic acid carboxylate. The C5-C10 monocarboxylic acid contains methylbutanoic acid and 3,5,5-trimethylhexanoic acid, and the ratio of the weight of methylbutanoic acid to the weight of 3,5,5-trimethylhexanoic acid is 3: is 7, the method of claim 1 or 6. The method according to claim 1 or 6 , wherein the C5-C10 monocarboxylic acid comprises methylbutanoic acid and neodecanoic acid, and the ratio of the weight of methylbutanoic acid to the weight of neodecanoic acid is 1: 3.   The method of claim 1, wherein the lubricant composition has a viscosity of 160-460 centistokes at 40 ° C. The chlorine-free hydrofluorocarbon refrigerant is R-134a,
-35 ° C when the lubricant composition is contained in the chlorine-free hydrofluorocarbon refrigerant at 20% by weight based on the total weight of the lubricant composition and the chlorine-free hydrofluorocarbon refrigerant. 10. The method of claim 9 , wherein at a lower temperature, the lubricant composition is miscible with the chlorine-free hydrofluorocarbon refrigerant.   The method of claim 1, wherein another lubricant or base stock composition is blended with the lubricant composition in a ratio of less than 20% based on the weight of the lubricant composition.   Oxidation resistance and thermal stability improver, corrosion inhibitor, metal deactivator, lubricity imparting agent, viscosity index improver, pour point and / or flock point depressant, detergent, dispersant, defoamer, acid scavenger One or more additives selected from the group consisting of an agent, an antiwear agent, and an extreme pressure resistor are the lubricant composition, the chlorine-free hydrofluorocarbon or the lubricant composition and the chlorine-free hydro The method of claim 1, wherein the method is mixed with a mixture of fluorocarbons in an amount of 3% or less than 3% based on the weight of the mixture.