JP2001262168A - Silicone-based refrigerating machine oil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide silicon-based refrigerating machine oil suitable for a use at a low temperature up to -70 deg.C, having excellent mixing stability, containing no salts, alcohols, carbon halides and halogenated hydrocarbons. SOLUTION: This silicon-based refrigerating machine oil comprises a siloxane oligomer of the general formula, RSi(OSiR3)3 (Rs are each the same or different and a 1-8C substituted or nonsubstituted monofunctional hydrocarbon group) as a main component and is used at a low temperature to -70 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention is suitable for use at low temperatures down to -70 ° C, has excellent compounding stability, and does not contain any of salts, alcohols, halocarbons or halogenated hydrocarbons. Related to refrigeration oil.

[0002]

^2. Description of the Related Art The viscosity at 20 ° C. is 5 to 20 mm ² /
It is known that silicone oils in seconds can be used for freezing (W. Simmler, "GIT.
G-IT fachzeitschrift fr das Laboratori
m) ", 6, 101, 189, 278-1962).
The viscosity of the silicone oils described here is low (−40).
° C) (viscosity: 25 mm ² / sec),
Since its use is static in nature, high viscosity at low temperatures is not a problem.

On the other hand, halocarbon and halogenated hydrocarbon compounds such as trichloromonofluoromethane (CFC 11), dichlorodifluoromethane (CFC 12), and monochlorodifluoromethane (CFC 22) are used as refrigerants for freezing the mechanical circuit itself. Has been low (about-
(80 ° C.). Depending on the temperature (about −40 ° C.), aqueous solutions of alcohols (such as methanol, ethanol and propylene glycol) and salts (particularly inorganic salts such as calcium chloride and soda) are used. However, alcohols generally have a low flash point, so lower alcohols require safety precautions, and in some cases are toxic. Aqueous salt solutions are very corrosive and have excessive viscosity at low temperatures. On the other hand, halocarbons and halogenated hydrocarbon compounds have the problem of partially contributing to the photochemical degradation of the ozone layer, and in some cases are also toxic. Thus, mixtures of silicone oils with halocarbons and halogenated hydrocarbons are not very valid.

Japanese Patent No. 2839162 discloses a mixture of decamethyltetrasiloxane, hexamethyldisiloxane, cyclic silicone, and the like, which are different from the branched structure of the siloxane oligomer used in the present invention. Since it is a chain silicone, it has a disadvantage that siloxane bonds are easily broken. In addition, recent refrigerators have been operated under severe conditions (inverters) and the number of revolutions of the compressor has been increased, so that the refrigerant has lubrication properties such as anti-seizure and abrasion resistance. Improvement is becoming an increasingly essential requirement. As a measure for improving the lubricity of such a refrigerant, a phosphorus-based compound such as tricresyl phosphate (TCP) or a sulfur-based compound such as dialkyl sulfide is blended as an antiwear agent in the base oil of the refrigerant. These compounds have the disadvantage that siloxane bonds, especially diorganosiloxanes, are easily cleaved.

[0005]

As described above, conventional non-silicone refrigeration oils suitable for use at low temperatures usually contain salts, alcohols, halocarbons or halogenated hydrocarbons, etc. Had various unresolved disadvantages associated with it. On the other hand, the conventional silicone-based refrigerating oil suitable for use at low temperatures is based on a chain silicone as described above, and has a problem from the viewpoint of stability. Further, it has not been found that the siloxane oligomer having a branched structure of the present application has characteristics suitable as a refrigerating oil, and no application using such a silicone oil as a refrigerating oil has been known.

[0006]

In the present application, a siloxane oligomer having a specific branched structure is used as a refrigerating oil which is stable even in a wide temperature range and can be used even at a low temperature of about -70 ° C. Was found to be extremely suitable for the use of. This stability is further enhanced by the use of tricresyl phosphate (T
It contains a phosphorus compound such as CP) or a sulfur compound such as dialkyl sulfide, and has excellent oxidation stability even under conditions where siloxane bonds are easily cleaved. In addition, refrigeration oil requires volatility as a refrigerant, a small change in viscosity due to temperature, thermal stability, etc., and is also added to a compressor oil for the purpose of improving lubricity with a compressor, corrosion resistance, and noise reduction. The silicone-based refrigerating oil of the present invention is excellent in these respects, though it requires compatibility with and chemical stability.

The silicone-based refrigeration oil of the present invention (ie,
Medium) avoids the above-mentioned drawbacks of the conventional refrigeration oil.
Salt, alcohol, halogenated hydrocarbon or
And does not contain any of the carbons, and has the general formula RSi (OSiR₃)₃  (Wherein, R may be the same or different
And a substituted or unsubstituted monovalent hydrocarbon group having 1 to 8 carbon atoms.
Represent. The siloxane oligomer represented by
Oil) as a main component and, if necessary, a dye.
And features.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The silicone refrigeration oil of the present invention
General formula RSi (OSiR₃)₃  (Wherein, R may be the same or different
And a substituted or unsubstituted monovalent hydrocarbon group having 1 to 8 carbon atoms.
Represent. The main component is a siloxane oligomer represented by
Including. In the above general formula, specific examples of R include a methyl group,
Ethyl, propyl, butyl, pentyl, hexyl
Alkyl, cyclopentyl, cyclohexyl
Cycloalkyl group such as phenyl group, phenyl group, tolyl group,
Aryl group such as silyl group, benzyl group, phenethyl group, etc.
Aralkyl, trifluoropropyl, nonafluoro
Examples thereof include a fluoroalkyl group such as a rohexyl group. Up
Examples of the siloxane oligomer represented by the general formula include:
Ris (trimethylsiloxy) methylsilane, tris (g
Trimethylsiloxy) propylsilane, tris (trimethyl)
(Silyloxy) phenylsilane and the like.
Sub (trimethylsiloxy) methylsilane is preferred. Ma
As a siloxane oligomer component, if necessary
RSi (OSiR ₃)₃Besides, decamethyltetracy
Linear silico such as loxane and octamethyltrisiloxane
Or octamethylcyclotetrasiloxane, decamethi
Add cyclic silicone such as
You may.

[0009] The silicone refrigerating oil of the present invention may further contain a dye. As these dyes, for example, anthraquinone, 1-aminoanthraquinone, 1,4-bis-isobutylaminoanthraquinone, 1- (3-dimethylaminopropylamino) -4-methylaminoanthraquinone, 1- (4-methylphenylamino)- Anthraquinone, 1,4-bis- (2,6-diethyl-4-methylphenylamino) -anthraquinone, 1,4-bis- (4
-Tert-butylphenylamino) -anthraquinone, 1-methylamino-4- (3-methylphenylamino) -anthraquinone, 1-methylamino-4- (4
-Methylphenylamino) -anthraquinone, 1- (3
Anthraquinone dyes such as -dimethylaminopropylamino) -4- (4-methylphenylamino) -anthraquinone, and Celeslot 7B, Celesgerb CRN;
Natural dyes such as coquineal and Ceresbrau GN are exemplified. These dyes are usually added to the base oil with stirring at room temperature and its color is used to indicate possible leakage to the siloxane oligomers of the present invention. The content of the dye is usually 0.001 to 0.01% by weight, preferably 0.002% by weight based on the siloxane oligomer of the present invention.
~ 0.01% by weight. Further, the silicone-based refrigeration oil of the present invention may contain a phosphorus-based compound such as tricresyl phosphate (TCP) or a sulfur-based compound such as dialkyl sulfide in order to improve lubricating properties. Provides excellent stability without breaking.

The siloxane oligomer of the present invention is produced, for example, by the following method. (1) It can be obtained by re-equilibrating hexaorganosisiloxane and organotrichlorosilane in the presence of a mixed acid of an inorganic acid and a Lewis acid (JP-A-2-247186). (2) It is obtained by substituting hexaorganodisiloxane and organotrialkoxysilane with siloxy groups in hexaorganodisiloxane in the presence of an acid catalyst and a carboxylic acid (JP-A-11-217584). (3) It can be obtained by performing a cohydrolysis reaction of triorganochlorosilane with organotrichlorosilane and water in the presence of an acid equilibrium catalyst (JP-A-49-81351). Among these production methods, the method (2) is preferable because the reaction proceeds under mild reaction conditions and the desired product can be obtained with high selectivity and high yield. The silicone-based refrigeration oil of the present invention may be the siloxane oligomer of the present invention alone or may be obtained by adding the above-mentioned dye and other components to the siloxane oligomer while stirring at room temperature.

[0011] The silicone-based refrigerating oil thus produced can be used at a low temperature of -70 ° C, preferably -70 to -3.
It is suitable for use as a refrigerant for freezing at a temperature of 0 ° C. and has a viscosity of 4 to ²⁰ mm ² / sec at these temperatures. That is, while this silicone-based refrigeration oil is preferably used for low-temperature storage and high-freezing equipment freezers, other heating / frozen liquids related to soil probes and heat pumps, as well as conventionally known It is also used for other heating / refrigeration liquids that can be cooled considerably after removing heat on the evaporator side of the heat pump, such as: Until now, these so-called saline systems, which are produced from a mixture of water and ethylene glycol, do not reach low temperatures. The silicone-based refrigeration oil of the present invention has the advantage of this type of application that it is non-corrosive and toxic safe. Under normal conditions, 19
Due to the high boiling point of 1 ° C., applications are also conceivable which are subjected to extreme temperature loads, such as, for example, automotive coolants or transformer oils in climates where a wide range of temperatures are encountered.

[0012]

【Example】Example 1  Tris (trimethylsiloxy) methylsilane 100 weight
To 0.5 parts by weight of tricresyl phosphate
Refrigeration oil and kept at -40 ° C.
Had an appropriate viscosity (viscosity: 5.7 mm²/
Seconds). In addition, this refrigeration oil is used in a refrigerator (Tokyo Rika Kikai Co., Ltd.)
Manufactured by CA-1500).
Functions as a refrigerant without any problems when operated under operating conditions
did. Conditions: Circulation volume 8 liters / min, 12 hours / day x 31 days

[0013]Example 2  The frozen oil was placed in a closed container and dried at 70 ° C.
Chromatography for 5 days with heat
As a result, no particular change was observed. Comparative
Instead of tris (trimethylsiloxy) methylsilane
Decamethyltetrasiloxane or octamethylcycline
Prepare the same frozen oil using rotetrasiloxane,
Test showed that the siloxane bond was broken.
(Ie, low molecular weight products are formed and
Viscosity was also reduced. ).

As can be seen from these results, the silicone refrigerating oil of the present invention comprising a branched siloxane oligomer represented by tris (trimethylsiloxy) methylsilane is used in a refrigerating apparatus which can be as low as about -70 ° C. Silicone refrigeration oil suitable for This silicone-based refrigeration oil does not contain salts, alcohols, halogenated hydrocarbons, and halocarbons, and is used as a base oil in a phosphorus-based compound such as tricresyl phosphate (TCP) or dialkyl as an antiwear agent. It has excellent oxidation stability even under conditions where a sulfur-based compound such as sulfide or the like is blended and siloxane bonds are easily cleaved.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C10N 30:20 C10N 30:20 40:30 40:30 F term (Reference) 4H104 BJ03A LA04 LA10 PA20 4J002 CP031 CP051 EE056 EN066 FD096 FD171 4J035 CA01N LA02 LB06

Claims (4)

[Claims] 1. The following general formula: RSi (OSiR₃)₃  (Wherein, R may be the same or different
And a substituted or unsubstituted monovalent hydrocarbon group having 1 to 8 carbon atoms.
Represent. The main component is a siloxane oligomer represented by
Silicone refrigeration used at temperatures as low as -70 ° C
oil. 2. The silicone-based refrigeration oil according to claim 1, further comprising 0.0001 to 0.01% by weight of a dye based on the siloxane oligomer. 3. The silicone refrigerating oil according to claim 1, which does not contain any of salts, alcohols, halocarbons and halogenated hydrocarbons. 4. The silicone refrigeration oil according to claim 1, wherein the siloxane oligomer is tris (trimethylsiloxy) methylsilane.