Coolant containing organopolysiloxane

Abstract

To provide a coolant which exhibits relatively excellent fluidity even at low temperatures and can be easily handled and stored due to having a high flash point.SOLUTION: This coolant includes an organopolysiloxane represented by formula (1) (wherein R1 is a C1-8 alkyl group or a phenyl group, and R2 is the group of R1 or the group of formula (2)).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an organopolysiloxane for use as a refrigerant. That is, the present invention relates to a refrigerant containing an organopolysiloxane, and more particularly to a refrigerant for use in a cooling device having a mechanism for forced circulation of the refrigerant. [Background technology]

[0002] Cooling systems that use forced circulation pumps or other devices to circulate refrigerants are used in a wide range of applications, including cooling electronic devices, heat exchange in manufacturing plants, and air conditioning. Operating temperatures range from cryogenic temperatures of around -60°C to high temperatures of around 150°C. Known refrigerant oils include mineral oil, alcohols, and halogenated hydrocarbons. However, mineral oils become highly viscous at low temperatures, placing a heavy load on the circulating pump. Alcohols are toxic and flammable, and halogenated hydrocarbons contribute to global warming, leading to their use being restricted. For these reasons, fluorinated refrigerants, which have low viscosity and low flammability even at low temperatures, have been widely used as refrigerant oils. However, the persistence of fluorinated compounds has become a concern in recent years, and restrictions on their use are being considered.

[0003] Given these circumstances, there is a demand for alternative refrigerants to fluorocarbons, and silicone oils, which maintain fluidity even at low temperatures, have attracted attention. The use of silicone oils as refrigerants has been investigated in the past (Patent Document 1). However, the specification stipulated that a flash point of 60°C or higher would be sufficient, but this standard is insufficient in light of Japan's Fire Service Act and other regulations. Mixtures of decamethyltetrasiloxane and hexamethyldisiloxane have also been proposed, but these have low fluidity at low temperatures but high volatility and flash points below 100°C (Patent Document 2). Refrigerants primarily composed of siloxane oligomers have also been proposed, but they also have excellent fluidity at low temperatures but a low flash point (Patent Document 3). The development of alternatives to fluorocarbons for refrigeration applications is an urgent issue, and there is a need for refrigerants that maintain fluidity at low temperatures and have a high flash point. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 07-166061 [Patent Document 2] Japanese Patent Application Publication No. 02-242878 [Patent Document 3] Japanese Patent Application Laid-Open No. 2001-262168 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a refrigerant that has relatively good fluidity even at low temperatures, a high flash point, and is easy to handle and store. [Means for solving the problem]

[0006] The present invention was made possible by the discovery that organopolysiloxanes having the specific structure shown below have low viscosity, flowability at low temperatures, and a high flash point, making them suitable as refrigerants in refrigerant circulation systems.

[0007] That is, the present invention is [1] A refrigerant containing an organopolysiloxane represented by the following formula (1) is provided. [ka] (In formula (1), R 1 are each independently a group selected from an alkyl group having 1 to 8 carbon atoms and a phenyl group, and R 2 is the above R 1 or a group defined by the following formula (2): [ka] wherein m is an integer of 3 to 6; In equation (2), R 3 are each independently an alkyl group having 1 to 4 carbon atoms, x is an integer of 2 to 6, and n is an integer of 1 to 30; All R in the formula (1) 2 at least two of which are groups represented by the formula (2).

[0008] Furthermore, the present invention provides the above refrigerant, which further has at least one component selected from the following: [2] The organopolysiloxane has a kinematic viscosity of 4 to 30 mm at 25°C, measured using a Cannon-Fenske viscometer according to JIS Z803:2011. 2 The above refrigerant having / s. [3] The above refrigerant, which is a refrigerant for a cooling device. [4] The above refrigerant, wherein the cooling device has a mechanism for forced circulation of the refrigerant. More preferably, the present invention provides a refrigerant comprising an organopolysiloxane represented by the above formula (1). [Effects of the Invention]

[0009] The organopolysiloxane compound of the present invention has a high flash point while maintaining good fluidity at low temperatures, and therefore can be used as a refrigerant oil over a wide temperature range. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention is a refrigerant containing an organopolysiloxane represented by the following formula (1): [ka] (In formula (1), R 1 are each independently a group selected from an alkyl group having 1 to 8 carbon atoms and a phenyl group, and R 2 is the above R 1 or a group defined by the following formula (2): [ka] wherein m is an integer of 3 to 6; In equation (2), R 3 are each independently an alkyl group having 1 to 4 carbon atoms, x is an integer of 2 to 6, and n is an integer of 1 to 30; All R in the formula (1) 2 At least two of these are groups represented by the formula (2).

[0011] In the above formula (1), R 1 Examples of the alkyl group include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, and octyl groups, and phenyl groups. Methyl, ethyl, and propyl groups are preferred. m is an integer of 3 to 6, preferably 4 or 5.

[0012] R 2 is the above R 1 or a monovalent group represented by the above formula (2). 3 Examples of the alkyl group include methyl, ethyl, propyl, and butyl groups, with methyl being preferred. x is an integer of 2 to 6, and preferably 2. n is a number representing the degree of polymerization of the siloxane. n is an integer of 1 to 30, and preferably 2 to 10. If n is greater than 30, the viscosity will be too high.

[0013] All R in the above formula (1) 2 At least two of the R 1 Of these, organopolysiloxanes having less than two groups represented by formula (2) have excellent fluidity at low temperatures, but have a low flash point.

[0014] The organopolysiloxane of the present invention has a kinematic viscosity of 4 to 30 mm as measured at 25°C using a Cannon-Fenske viscometer according to JIS Z803:2011. 2 / s, and 4 to 20 mm 2 / s. In order to use it as a refrigerant for a cooling device, it is more preferable that the kinematic viscosity at -20°C is 150 mm 2 / s or less, and 10 to 100 mm 2 / s, preferably 10 to 80 mm 2If the kinematic viscosity at -20°C exceeds the upper limit, the load on the circulation pump increases. In the present invention, the kinematic viscosity at 0°C or below, for example, at -20°C and -40°C, is a value measured using a rheometer in an environmental test chamber cooled with liquid nitrogen under the following conditions. [Measurement conditions] Equipment: DHR-2, environmental test chamber (manufactured by TA Instruments) Shear rate::1,000s -1 Plate: Aluminum parallel plate (upper diameter 25 mm, lower diameter 40 mm, gap 0.5 mm) The absolute viscosity obtained as a measurement result was converted to kinematic viscosity using the following formula (a) from the absolute viscosity and specific gravity at the measurement temperature T°C. The specific gravity (T°C) at the measurement temperature T°C was calculated using the following formula (b). Kinematic viscosity (T℃) = Absolute viscosity (T℃) / Specific gravity (T℃) Formula (a) Specific gravity (T℃)=0.0009×(25-T)+specific gravity (25℃) Formula (b) If the refrigerant content falls within the above range, it can be used as a refrigerant with fluidity suitable for a cooling device having a mechanism for forced circulation of the refrigerant.

[0015] The polysiloxane of the present invention can be synthesized, for example, by addition reaction of a cyclic hydrogenpolysiloxane represented by the following formula (3) with a polysiloxane having an unsaturated bond at its terminal represented by the following formula (4) in the presence of a platinum catalyst or a rhodium catalyst. [ka] [ka]

[0016] The organopolysiloxane represented by the above formula (4) can be obtained by a commonly known method, for example, by ring-opening polymerization of hexamethylcyclotrisiloxane using a pentacoordinate silicon complex catalyst or an anionic polymerization catalyst, and then terminating the reaction with vinyldimethylchlorosilane.

[0017] The addition reaction can be carried out in an organic solvent or without a solvent. Examples of organic solvents include alcohols such as ethanol and 2-propanol, aromatic hydrocarbons such as toluene and xylene, hydrocarbons such as n-pentane and n-hexane, and cyclohexane. The addition reaction is not particularly limited, but it is desirable to carry out the reaction under reflux for 1 to 8 hours. If necessary, ethylene or propylene gas may be blown in to further carry out the addition reaction. After the addition reaction, the solvent and low-molecular-weight components can be removed by heating at 100°C to 120°C under reduced pressure to obtain the desired organopolysiloxane.

[0018] It is desirable that the flash point of the refrigerant be higher than the temperature at which it is used. The organopolysiloxane of the present invention preferably has a flash point of 150°C or higher, more preferably 160°C to 300°C. The flash point in the present invention is measured by the Cleveland Open Method described in JIS K2265-4:2007. Because it is difficult to accurately measure the flash point at or above 300°C, the upper limit of the preferred flash point is set to 300°C, but flash points higher than this can also be used preferably.

[0019] The refrigerant of the present invention can be suitably used as a refrigerant for a cooling device having a mechanism for forced circulation of the refrigerant, such as a refrigerant storage tank, a refrigerant circulation device, a refrigerator for cooling the refrigerant, or a commonly known forced circulation cooling device using a heat exchanger. [Example]

[0020] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0021] [Example 1] A reaction vessel was charged with 162 g of an organohydrogensiloxane represented by the following formula (5) and 600 g of toluene, to which 1 g of a 0.5 wt % toluene solution of chloroplatinic acid was added, and the reaction was carried out for 5 hours under reflux while 544 g of an organosiloxane represented by the following formula (6) was added dropwise. After the reaction, the solvent and low-molecular-weight components were removed by heating to 100 to 120°C under reduced pressure, yielding 670 g of a colorless, transparent organopolysiloxane. [ka] [ka] The resulting organopolysiloxane is represented by the above formula (1), and R 1 are all methyl groups, m is 4, and two R 2 is a propyl group, and two R 2 is a group represented by the above formula (2), and in formula (2), R 3 are all methyl groups, x is 2, and n is 6.

[0022] [Example 2] A reaction vessel was charged with 72 g of an organohydrogensiloxane represented by formula (7) below and 600 g of toluene, to which 1 g of a 0.5 wt % toluene solution of chloroplatinic acid was added. 470 g of an organosiloxane represented by formula (8) below was added dropwise while refluxing the solvent, and the reaction was continued for 6 hours. Ethylene gas was then blown in while the reaction continued for an additional 4 hours. After the reaction, the solvent and low-molecular-weight components were removed by heating to 100-120°C under reduced pressure, yielding 510 g of a colorless, transparent organopolysiloxane. [ka] [ka] The resulting organopolysiloxane is represented by the above formula (1), and R 1 are all methyl groups, m is 4, and four R 2 is a group represented by the above formula (2), and in formula (2), R3 are all methyl groups, x is 2, and n is 4.

[0023] The properties of the organopolysiloxanes obtained in Examples 1 and 2 are shown in Table 1. The flash point was measured using a Cleveland open-type flask according to JIS K2265-4:2007. The kinematic viscosities at 20°C, 25°C, 50°C, and 100°C were measured using a Cannon-Fenske viscometer according to the method described in JIS Z8803:2011. The kinematic viscosities at 0°C, -20°C and -40°C were measured using a rotational rheometer according to the conditions described above.

[0024] [Table 1]

[0025] The organopolysiloxanes obtained in Examples 1 and 2 above were used as refrigerants in a cooling water circulation system (CCA-1112, manufactured by Tokyo Rikakikai Co., Ltd.) and operated at −20°C and 30°C for 30 days (12 hours / day), respectively, confirming that they could be used as refrigerants.

[0026] As described above, the organopolysiloxane of the present invention has low viscosity, good fluidity at low temperatures, and a high flash point, and therefore can be safely used as a refrigerant oil in cooling systems that have a mechanism for forced refrigerant circulation.

Claims

1. A refrigerant containing an organopolysiloxane represented by the following formula (1): 【Chemistry 1】 (In formula (1), R １ are each independently a group selected from an alkyl group having 1 to 8 carbon atoms and a phenyl group, and R ２ is the R １ or a group defined by the following formula (2): 【Chemistry 2】 wherein m is an integer of 3 to 6; In formula (2), R ３ are each independently an alkyl group having 1 to 4 carbon atoms, x is an integer from 2 to 6, and n is an integer from 1 to 30; All R in the formula (1) ２ At least two of these are groups represented by the formula (2).

2. The organopolysiloxane has a kinematic viscosity of 4 to 30 mm at 25°C as measured by a Cannon-Fenske viscometer according to JIS Z803:2011. ２ 10. The refrigerant of claim 1 having a .OMEGA. / s.

3. The refrigerant according to claim 1 or 2, which is a refrigerant for a cooling device.

4. The refrigerant according to claim 3, wherein the cooling device has a mechanism for forced circulation of the refrigerant.

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