JPH02227487A - Working medium for freezer and freezer using the same medium - Google Patents

Abstract

PURPOSE:To provide the subject working medium containing a fluorinated hydrocarbon and a fluorine-modified polysiloxane in a specified ratio, free from two-phase separation to low temperatures and destruction of the ozone layer, having a minimized moisture absorption and excellent in heat resistance and lubricity. CONSTITUTION:An objective working medium containing (A) 95-40wt.% fluorinated hydrocarbon (e.g. 1,1,1,2-tetrafluoroethane, 1,1,2,2-tetrafluoroethane or hexafluorocyclopropane) prepared by substituting a part or the whole of H of a 2-4C hydrocarbon with F and having >=40 deg.C critical temperature and (B) 5-60wt.% fluorine-modified polysiloxane preferably represented by the formula (m is 0-5; n is value where kinematic viscosity at 25 deg.C is 100-10000cSt). The above-mentioned working medium is effective for improving efficiency of a freezer of air-conditioners, refrigerators, etc., and for improvement of durability thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a refrigeration system equipped with a working medium containing a fluorine-based refrigerant and a refrigeration compressor using the working medium.

[Background Art] In recent years, in the field of refrigeration equipment such as refrigerators and air conditioners, refrigeration compressors have been made smaller and more efficient. In particular, there is an increasing demand for rapid freezing in refrigerators, and in order to meet this demand, the rotation speed of refrigeration compressors (hereinafter referred to as compressors) has been increasing.

Due to the high-speed rotation of the compressor, the discharge temperature of the refrigerant from the compressor is higher than ever before, so a working fluid consisting of a refrigerant and lubricating oil with excellent heat resistance is required.

As a refrigerant for refrigeration equipment such as refrigerators and air conditioners, dichlorodifluoromethane (CCl2F3; R12), which is a type of halogenated hydrocarbon, is used as a refrigerant for lubricating oils such as naphthenic and paraffinic mineral oils, which are internal lubricating oils. It is widely used because of its good compatibility.

However, the use of R,12 is about to be regulated due to environmental problems such as destroying the earth's ozone layer.

An alternative is required.

Possible refrigerants include hydrofluorocarbons or fluorocarbons having a boiling point close to that of R12.

However, the above-mentioned refrigerant has the disadvantage of extremely poor compatibility with general mineral oil-based lubricating oil [refrigeration: 60816 (19
1985)], this is thought to be because it does not have chlorine as a substituent for hydrogen in the molecule like R12 [ASHRE Guide and Data Book (ASHRE
Guide and Data Book, ) No. 307
(1969)).

As a lubricating oil that dissolves in the hydrofluorocarbon or fluorocarbon-based refrigerant, a bifunctional or higher-functional polyoxylene glycol having an OH group at the end has been proposed (U.S. Pat. No. 4,755,316). However, it has the drawbacks of being susceptible to oxidative deterioration and being highly hygroscopic.

In addition, fluorine-modified polysiloxane is known as a lubricating oil for low-temperature refrigeration equipment (Japanese Patent Application Laid-Open No. 63-256694
The refrigerants used in this are dichlorodifluoromethane (R12), monochlorotrifluoromethane (R13), and monochlorodifluoromethane (R2).
2) and monochloropentafluoroethane (R115) (h<502), or trifluoromethane (R23) and monochlorotrifluoromethane (R13
) is an azeotrope (R503).

All of the above refrigerants contain hydrofluorochlorocarbon or fluorochlorocarbon, and contain chlorine as a substituent, which is said to destroy the ozone layer in the atmosphere.

Furthermore, trifluoropropylmethylpolysiloxane is added to paraffinic and naphthenic mineral oils at O0],
A refrigerating machine oil has been proposed (Japanese Patent Application Laid-Open No. 105091/1989) in which 30 ppm of O is added to prevent foaming, but with this amount of addition, sufficient characteristics are obtained as a working medium for a high-speed rotation compressor. It is not possible.

[Problems to be Solved by the Invention] The problems to be solved by the present invention will be specifically explained using a car air conditioner as an example of a refrigeration system.

FIG. 1 shows a sectional view of a car air conditioner compressor, and FIG. 2 shows a schematic diagram of a refrigeration system.

The compressor is driven by transmitting the rotational force of the engine to the pulley 1 via the V-belt, and the drive and stop are performed by turning on and off the current to the coil 2 of the magnetic clutch.
F is performed to engage and disengage the clutch.

The rotational force of the engine rotates the swash plate 5 attached to the shaft 9 of the compressor, thereby causing the slipper 6 and the ball 7 to rotate.
The piston 4 is driven left and right through the . The piston 4 functions to compress low-pressure refrigerant to high pressure and send it out when driven.

The compressor is incorporated into a refrigeration system as shown in FIG.

First, the refrigerant vapor sucked into the compressor 12 weighs approximately 15 kg.
/cm" and reaches a high temperature, and enters the condenser 13 through the refrigerant distribution pipe 19 along the arrow in the figure. The compressed high-temperature refrigerant vapor is passed through the radiator fan 1 in the condenser 13.
8 and liquefied. The liquefied refrigerant is temporarily stored in a liquid tank 14, then sent to an expansion valve 15, ejected from a small hole, and enters an evaporator (heat exchanger) 16. The pressure becomes about 2 kg/am'', the temperature drops rapidly, and the evaporator 16 absorbs the surrounding heat and vaporizes it.

The cold energy obtained by the evaporator 16 is sent out as cold air by the blower 17 to cool the interior of the vehicle.

The vaporized refrigerant is returned to the compressor 12 and compressed. Car air conditioners are made up of these cycles.

Refrigeration devices such as room air conditioners and refrigerators are also constructed based on almost the same principle as described above. Although FIG. 1 shows an example of a swash plate layer compressor, there are other types such as a single swash plate type, a screw type, a rotary type, and a scroll type. In addition, for refrigerators, there are reciprocating types, rolling piston types, etc.
Their functions are the same as those of the car air conditioner.

By the way, these compressors are equipped with thrust bearings 3. There are sliding parts such as a swash plate 5 and slippers 6. Lubrication of these sliding parts.

This is done by pumping and supplying a working medium, which is a mixture of refrigerant and lubricating oil, from an oil chamber 10 provided at the bottom of the compressor using a gear pump 8.

However, if the compatibility between the refrigerant in the working medium and the lubricating oil is poor,
Both refrigerants are separated into two layers within the compressor, and the refrigerant with a higher specific gravity stays in the lower layer, so that only the refrigerant is supplied to the sliding parts.

However, because the refrigerant has a very low viscosity.

Even if oil is supplied to sliding parts, it may form an oil film, increasing friction, wear, or seizing.

On the other hand, as shown in Fig. 2, most of the refrigerant is compressed by the compressor 12 and transported to the condenser 13, expansion valve 15, evaporator 16 and refrigeration cycle where it takes part in the refrigeration work. A portion of the refrigerant also circulates within the cycle. At this time, since the temperature becomes low in the evaporator 16, if the refrigerant and lubricating oil have poor compatibility, they will separate, and high viscosity lubricating oil will stay and accumulate there, reducing the heat exchange efficiency of the evaporator 16. Furthermore, this causes a shortage of lubricating oil in the compressor 12.

The polyoxylene glycol has excellent compatibility with refrigerants, but since it easily contains water, it is not easy to dehydrate it. Therefore, if it is used without sufficient dehydration, the water contained in it will be lost. It may freeze in the evaporator 16 of the refrigeration system or clog the expansion valve provided in the vicinity.

Furthermore, when polyoxylene glycol is used in car air conditioners, etc., it is said that in addition to causing the above-mentioned problems due to moisture seeping in from rubber pipes and other piping, polyoxylene glycol is also prone to hydrolysis and self-degradation due to such moisture. There are drawbacks.

Furthermore, polyoxylene glycol inevitably has inferior lubrication performance in a high-temperature compressor compared to lubricating oils such as mineral oil.

The present invention has been made in view of these circumstances, and its purpose is to ensure that the hydrofluorocarbon or fluorocarbon refrigerant and the lubricating oil always have a stable homogeneous phase, thereby providing excellent heat resistance and lubricity. An object of the present invention is to provide a medium and a refrigeration device using the working medium.

[Means to solve the problem] The gist of the present invention is as follows.

(1) 95 to 40% by weight of a fluorinated hydrocarbon in which part or all of the hydrogen in a hydrocarbon having 2 to 4 carbon atoms is replaced with fluorine.
and 5 to 60% by weight of a fluorine-modified polysiloxane.

(2) The working fluid for a refrigeration device as described in (1) above, wherein the fluorinated hydrocarbon has a critical temperature of 40° C. or higher.

(3) The above item, wherein the fluorinated hydrocarbon is at least one of 1,1,1,2-tetrafluoroethane, 1,1,2,2-tetrafluoroethane, and hexafluorocyclopropane. (1) or (2
) Working medium for refrigeration equipment.

(4) The fluorine-modified polysiloxane has the following general formula (
1) (In the formula, 1m is 0 to 5, and n is a value such that the kinematic viscosity at 25°C of the fluorine-modified polysiloxane is 100 to, ooo centistokes.) The working medium for a refrigeration device according to any one of the above items (1) to (3).

(5) A refrigeration compressor, a condenser that condenses the refrigerant compressed by the refrigeration compressor, an expansion valve that injects the refrigerant condensed by the condenser through small holes and expands it, and cools the refrigerant expanded by the expansion valve. In a refrigeration system equipped with a heat exchanger, the working medium of the refrigeration compressor is fluorinated hydrocarbon water in which part or all of the hydrogen in a hydrocarbon having 2 to 4 carbon atoms is replaced with fluorine. A refrigeration device comprising 195 to 40% by weight of a fluorine-modified polysiloxane and 5 to 60% by weight of a fluorine-modified polysiloxane.

(6) The refrigeration apparatus according to item (5) above, wherein the fluorinated hydrocarbon has a critical temperature of 40° C. or higher.

(7) The above item, wherein the fluorinated hydrocarbon is at least one of 1,1,1,2-tetrafluoroethane, 1,1,2,2-tetrafluoroethane, and hexafluorocyclopropane. (5) or (6
) refrigeration equipment.

(8) The fluorine-modified polysiloxane has the following general formula (
1) It is a fluorine-modified polysiloxane represented by (wherein, m is O to 5, and n is a value such that the kinematic viscosity at 25°C of the fluorine-modified polysiloxane is 100 to, ooo centistokes). The refrigeration apparatus according to any one of the preceding clauses (5) to (7), characterized by:

The fluorinated hydrocarbon used in the present invention has superior heat resistance compared to conventional dichlorodifluoromethane (R12) and does not contain a chlorine substituent, so there is no fear of environmental damage such as destruction of ozone in the atmosphere.

As the above fluorinated hydrocarbon, pentafluoroethane (
R125), 1,1,2,2-tetrafluoroethane (R134), 1,1. i, 2-tetrafluoroethane (R134a), 1,1.2-trifluoroethane (R143), 1,1.1-trifluoroethane (R1
43a), 1,1-difluoroethane (R152a)
, monofluoroethane (R161), hexafluoropropane (R216) and octafluorocyclobutane (R318).

These refrigerants have a critical temperature of 40°C or higher.

It can be used in general refrigeration equipment with a condensing temperature of 40°C or higher.

Among these, 1,1,2,2-tetrafluoroethane (R134), 1,1,1,2-tetrafluoroethane (R134a), hexafluoropropane (
R216) is ±10°C of the boiling point of R12 (29.8°C)
The discharge pressure is not much different from R12, so
Refrigeration equipment that uses conventional R12 can be used as is.

Note that two or more types of the above-mentioned refrigerants can be used in combination depending on the purpose.

As is clear from the examples below, the compatibility with the lubricating oil represented by the general formula (1) is as follows at any concentration:
They are compatible down to low temperatures (-50°C) and can achieve the object of the present invention.

In the working medium of the present invention, the general formula [! ] Examples of the fluorine-modified polysiloxane include FS-1265Fluid manufactured by Dow Corning, fluorosilicone oil FQF510 manufactured by Toshiba Silicone, or polymethyl-3,3,3-trifluoropropyl manufactured by Chisso Corporation. There are siloxanes, etc.

The saturated water content of the fluorine-modified polysiloxane is 3 to several hundred ppm of the polyoxylene glycol.
Extremely low at 0 ppm or less, and has excellent lubricity, heat resistance,
It also has excellent chemical resistance.

In the working fluid of the present invention, the content of the fluorine-modified polysiloxane is limited to 5 to 60% by weight because if it is less than 5% by weight, sufficient lubrication performance cannot be obtained, so the movable parts of the compressor may seize. This is because, if the content exceeds 60% by weight, it will no longer function as a refrigerant in a refrigeration system.

Note that an antifoaming agent, an extreme pressure agent for improving lubricity, or the like may be added to the working medium as long as it does not impede the object of the present invention.

[Function] In the present invention, the fluorine-modified polysiloxane has -CH, CH, -(CFyo)--CF3 groups in its molecule, and is a fluorinated hydrocarbon of the refrigerant used.

For example, 1,1,1,2-tetrafluoroethane (CF3
-CH,F) and is considered to have excellent compatibility because its molecular structure is similar.

As a result, the sliding parts of the compressor can be sufficiently lubricated, so that the rotation speed of the compressor of the refrigeration system can be increased.

Next, one embodiment of the present invention will be specifically explained using examples.

Examples 1 to 3 and Comparative Examples 1 to 8 The critical solubility temperatures of three types of fluorine-modified polysiloxanes having viscosities of 100 cSt, 300 cSt, and 10,000 cSt at 25° C. and fluorohydrocarbon refrigerants were measured. For comparison, we also measured the critical melting temperature of naphthenic mineral oil (viscosity 100 cSt at 40°C), alkylbenzene (viscosity 34 cst at 40°C), and various liquids used in conventional air conditioners and refrigerators and fluorohydrocarbon refrigerants. did.

The critical melting temperature was measured in the following manner.

Insert a thermometer into a sample container made of pressure-resistant glass (capacity 100 mj2) with a valve on the head so that liquefied gas can be sealed, and add a certain amount of lubricating oil (for example, 3.5 mff1 fluorine-modified polysiloxane). and weigh it. After attaching the container to the refrigerant introduction device and evacuating the system, introduce about 60 mm of fluorinated hydrocarbon refrigerant from the refrigerant cylinder into the container while cooling in a dry ice/methanol bath, and close the valve. Shake well to make a homogeneous phase. In this way, the lubricating oil concentration was determined by weighing each container containing the various working media.

Then, it is gradually cooled again in a dry ice/methanol bath. Remove from time to time during cooling and shake well. The temperature at the time when turbidity was observed in the working medium was measured with the thermometer inserted into the container, and was defined as the two-phase separation temperature.

Next, in order to change the lubricating oil concentration, the temperature of the container is raised to around room temperature, the amount of refrigerant is reduced by opening the valve of the container and some of the refrigerant is released, and after reweighing, the container is cooled in the same manner as above. Find the two-phase separation temperature.

By repeating the above operation, the relationship between the two-phase separation temperature and the lubricating oil concentration was determined. The 3rd tendency to be internal
As shown in the figure.

Generally, the highest critical melting temperature (U
Only curves with C8T) appear. No two-phase separation is observed above this critical melting temperature.

However, in the case of high-viscosity polyglycol, the curve shows a U-shaped minimum critical solution temperature (LCST) as shown by curve 1, indicating that there is a region where two phases separate even on the high temperature side.

The critical melting temperatures of Examples and Comparative Examples are summarized in Tables 1 and 2.

As is clear from Table 1, the following examples are shown in Examples 1 to 3: 1.
In the case of 1.1.2-tetrafluoroethane and fluorine-modified polysiloxane, no two-phase separation was observed within the temperature range of -50°C to 50°C at any lubricating oil concentration. That is, curves corresponding to curves A and H in FIG. 3 did not appear.

On the other hand, with the low viscosity polyglycol (n=16) represented by the following formula (II) of Comparative Example 1, no two-phase separation was similarly observed, but with the high viscosity polyglycol of Comparative Example 2 (n
=21), UC:ST knee 30℃, LC8T:
0°C was observed.

H,C:4O-(-CH2-CH-0-)n-H(n)
CH.

Among Comparative Examples 3 to 8, which one has the lowest critical melting temperature.

With dioctyl sebacate of Comparative Example 5, UC8T: 30°C
Met. In all other cases, UC5T is higher than 50°C.

Table 2 Table 2 shows 1,1,2,2-tetrafluoroethane, hexafluorocyclopropane, and isostatic compounds of 1,1°1,2-tetrafluoroethane and hexafluorocyclopropane, This is a comparison of the critical melting temperatures when the lubricating oils used in Example 1 and Comparative Example 5 are combined.

When the fluorine-modified polysiloxane of Example 1 is combined, the UC8T is lower than -50°C in all cases, and the compatibility is much better than when combined with dioctyl sebacate of Comparative Example 5. I understand that.

[Effects of the Invention] In the working fluid containing the specific fluorinated hydrocarbon refrigerant and fluorine-modified polysiloxane of the present invention, two-phase separation between the two does not occur even at low temperatures, and even if the refrigerant leaks into the atmosphere, ozone destruction will occur. Since there is no need to worry about this, it is extremely suitable as a working medium for refrigeration equipment.

In addition, the fluorine-modified polysiloxane, which is the lubricating oil of the working medium of the present invention, has extremely low hygroscopicity and excellent heat resistance and lubricity, so it can improve the efficiency and extend the lifespan of refrigeration equipment such as air conditioners and refrigerators. It is extremely effective for improvement.

[Brief explanation of the drawing]

Figure 1 is a vertical cross-sectional view of a swash plate compressor for a car air conditioner, Figure 2 is a schematic diagram of the refrigeration cycle of a car air conditioner, and Figure 3 is a schematic diagram of the refrigeration cycle of a car air conditioner.
The figure is a graph showing the relationship between the two-phase separation temperature of refrigerant and lubricating oil and oil concentration. 1... Pulley, 2... Coil, 3... Thrust bearing, 4... Piston, 5... Swash plate, 6...
Slippers, 7...balls, 8...gear pumps, 9.
... Shaft, 10... Lubricating oil chamber, 11... Shaft seal, 12... Compressor, 13... Condenser, 14
...Liquid tank, 15...Expansion valve, 16...Evaporator (heat exchanger), 17...Blower, 18...Radiator fan, 19...Refrigerant delivery pipe. 20 19-Pulley 2--Coil 5--Piston 5--← Machine 1--Ball 9--Shaft 10-Issho slide 5 Yui Oil 1 Associate (! amount

Claims (1)

[Claims] 1. 95 to 40% by weight of a fluorinated hydrocarbon in which part or all of the hydrogen in a hydrocarbon having 2 to 4 carbon atoms has been replaced with fluorine, and 5 to 60% by weight of a fluorine-modified polysiloxane. A working medium for a refrigeration device, comprising: 2. The working fluid for a refrigeration system according to claim 1, wherein the fluorinated hydrocarbon has a critical temperature of 40° C. or higher. 3. A claim characterized in that the fluorinated hydrocarbon is at least one of 1,1,1,2-tetrafluoroethane, 1,1,2,2-tetrafluoroethane, and hexafluorocyclopropane. The working medium for a refrigeration device according to item 1 or 2. 4. The fluorine-modified polysiloxane has the following general formula [
I ] ▲ There are mathematical formulas, chemical formulas, tables, etc. 4. The working fluid for a refrigeration system according to claim 1, wherein the working fluid is a fluorine-modified polysiloxane represented by: 5. A refrigeration compressor, a condenser that condenses the refrigerant compressed by the refrigeration compressor, an expansion valve that injects the refrigerant condensed by the condenser through small holes and expands it, and exchanges the cold heat of the refrigerant expanded by the expansion valve. In a refrigeration system equipped with a heat exchanger, the working medium of the refrigeration compressor is 95 to 40% by weight of a fluorinated hydrocarbon in which part or all of the hydrogen in a hydrocarbon having 2 to 4 carbon atoms is replaced with fluorine. , fluorine-modified polysiloxane 5
A refrigeration device comprising ~60% by weight. 6. The refrigeration system according to claim 5, wherein the fluorinated hydrocarbon has a critical temperature of 40° C. or higher. 7. A claim characterized in that the fluorinated hydrocarbon is at least one of 1,1,1,2-tetrafluoroethane, 1,1,2,2-tetrafluoroethane, and hexafluorocyclopropane. The refrigeration device according to item 5 or 6. 8. The fluorine-modified polysiloxane has the following general formula [
I ] ▲ There are mathematical formulas, chemical formulas, tables, etc. 8. The refrigeration device according to claim 5, wherein the refrigeration device is a fluorine-modified polysiloxane represented by the following formula.