Refrigerant containing organopolysiloxane

Abstract

[Problem] The purpose is to provide an organopolysiloxane that can serve as a fluorocarbon replacement and is suitable as a refrigerant for refrigerant applications, especially as a refrigerant for cooling devices having a mechanism for forcibly circulating a refrigerant. [Solution] This refrigerant contains a linear organopolysiloxane represented by formula (1) (wherein, R1 are each independently a C1-4 alkyl group and n is an integer of 5-80). The linear organopolysiloxane has a weight average molecular weight of 1,000-5,000 and a molecular weight distribution [weight average molecular weight (Mw) / number average molecular weight (Mn)] of 1.2 or less.

Description

Refrigerant containing organopolysiloxane

[0001] 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.

[0002] Cooling systems that use forced circulation pumps or other devices to circulate refrigerants have a wide range of applications, including cooling electronic devices, heat exchange in manufacturing plants, and air conditioning. Operating temperatures range from approximately -60°C to 150°C. Known refrigerant oils include mineral oils, alcohols, and halogenated hydrocarbons. Mineral oils become highly viscous at low temperatures, placing a heavy load on the circulating pump, while alcohols pose problems due to their toxicity and flammability. Among halogenated hydrocarbons, chlorinated hydrocarbons are regulated due to their contribution to global warming. For these reasons, fluorocarbons, which have low viscosity and low flammability even at low temperatures, have been widely used as refrigerant oils. However, the persistence of fluorocarbons has become a concern in recent years, and restrictions on their use are being considered.

[0003] For these reasons, there is a demand for alternative refrigerants to fluorocarbons, and silicone oils that 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 was sufficient, but in light of Japan's Fire Service Act, this standard is insufficient. 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 has been a need for refrigerants that maintain fluidity at low temperatures and have a high flash point.

[0004] JP 07-166061 JP 02-242878 JP 2001-262168

[0005] An object of the present invention is to provide an organopolysiloxane that is suitable for use as a refrigerant, particularly as a refrigerant for cooling devices having a mechanism for forced refrigerant circulation, and that can serve as a substitute for fluorocarbons.

[0006] The present inventors discovered that organopolysiloxanes that are non-reactive, have narrow molecular weight distributions, and are nearly monodisperse, exhibit fluidity at low temperatures while also having high flash points, and are therefore suitable as refrigerants, particularly as refrigerants for cooling devices that have a mechanism for forced refrigerant circulation.

[0007] That is, the present invention provides: [1] a refrigerant containing a linear organopolysiloxane represented by the following formula (1): (Here, R １ are each independently an alkyl group having 1 to 4 carbon atoms, and n is an integer of 5 to 80. The linear organopolysiloxane has a weight average molecular weight of 1,000 to 5,000, and a molecular weight distribution [weight average molecular weight (Mw) / number average molecular weight (Mn)] of 1.2 or less.

[0008] Furthermore, the present invention provides the above refrigerant further having at least one component selected from the following: [2] In the above formula (1), R １

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[0009] The linear organopolysiloxane of the present invention maintains good fluidity at low temperatures and has a high flash point, making it usable as a refrigerant over a wide temperature range.

[0010] The present invention relates to a compound represented by the following formula (1): The refrigerant is more preferably a refrigerant for use in a cooling device, and particularly preferably a refrigerant for use in a cooling device having a mechanism for forced circulation of the refrigerant.

[0011] In the above formula (1), R １ are each independently an alkyl group having 1 to 4 carbon atoms, preferably a methyl group or an n-butyl group, and n is an integer of 5 to 80, preferably an integer of 10 to 70.

[0012] The linear organopolysiloxane has a weight-average molecular weight of 1,000 to 5,000, preferably 1,200 to 4,500. The molecular weight distribution [weight-average molecular weight (Mw) / number-average molecular weight (Mn)] is 1.2 or less, preferably 1.05 to 1.15. If the weight-average molecular weight of the linear organopolysiloxane is greater than 5,000, the flash point is improved, but the viscosity increases at low temperatures, increasing the load on the pump. If the weight-average molecular weight of the linear organopolysiloxane is less than 1,000, the fluidity at low temperatures is improved, but the flash point is lowered. Furthermore, if the molecular weight distribution (Mw / Mn) exceeds 1.2, i.e., if the molecular weight distribution is broad, the amounts of low-molecular-weight components and high-molecular-weight components increase. An increase in the low-molecular-weight components lowers the flash point, while an increase in the high-molecular-weight components increases the viscosity at low temperatures.

[0013] In the present invention, the molecular weight distribution, weight average molecular weight, and number average molecular weight are measured by GPC (gel permeation chromatography) analysis using polystyrene as a standard under the conditions shown below. [Measurement conditions] Developing solvent: toluene Flow rate: 0.6 mL / min Detector: differential refractive index detector (RI) Column: TSK Guard column Super H-H TSKgel Super H5000 (6.0 mm I.D. x 15 cm x 1) TSKgel Super H4000 (6.0 mm I.D. x 15 cm x 1) TSKgel Super H3000 (6.0 mm I.D. x 15 cm x 1) TSKgel Super H2000 (6.0 mm I.D. x 15 cm x 1) (all manufactured by Tosoh Corporation) Column temperature: 40°C Sample injection volume: 50 μL (toluene solution with a concentration of 0.3% by mass)

[0014] In the present invention, the value of n was measured under the following conditions: ２９ It can be determined from the Si-NMR spectrum. [Measurement conditions] Measurement solvent: deuterated chloroform Sample concentration: 30 mass % Relaxation reagent: chromium (III) acetylacetonate Number of accumulations: 2000 Apparatus name: JNM-ECX-500II (manufactured by JEOL Ltd.)

[0015] The organopolysiloxane used in the present invention is non-reactive and has a narrow molecular weight distribution. It can be produced by any conventional method, for example, by ring-opening polymerization of hexamethylcyclotrisiloxane at 0°C to 50°C for 2 to 8 hours using an organolithium compound as an anionic polymerization initiator and tetrahydrofuran as a solvent, terminating the reaction with trimethylchlorosilane as a terminal terminator, and then heating to 80°C to 130°C under reduced pressure to remove the solvent and low-molecular-weight components.

[0016] It is desirable that the flash point of the refrigerant be higher than the temperature at which it is used. The linear organopolysiloxane of the present invention preferably has a flash point of 150°C or higher, more preferably 200°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.

[0017] The linear organopolysiloxane of the present invention has a kinematic viscosity of 30 mm at 25°C. ２ / s or less, and 5 to 26 mm ２ / s, preferably 5 to 10 mm ２ In order to be used as a refrigerant for a cooling device, the kinematic viscosity at -20°C should be 150 mm / s. ２ / s or less, preferably 10 to 100 mm ２ / s, more preferably 15 to 90 mm ２ / s, more preferably 30 to 80 mm ２ / s. If 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 25°C is a value measured using a Cannon-Fenske viscometer according to the method described in JIS Z8803:2011. In the present invention, the kinematic viscosity at 0°C or lower, for example, at -20°C, -40°C, or -60°C, is a value measured using a rheometer in an environmental test chamber cooled with liquid nitrogen under the following conditions. [Measurement conditions] Apparatus: DHR-2, environmental test chamber (manufactured by TA Instruments) Shear rate: 1000 s ー１ Plates: Aluminum parallel plates (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 measurement temperature T°C. Note that the specific gravity (T°C) at measurement temperature T°C was calculated using the following formula (b): Kinematic viscosity (T°C) = absolute viscosity (T°C) / specific gravity (T°C) Formula (a) Specific gravity (T°C) = 0.0009 x (25 - T) + specific gravity (25°C) Formula (b)

[0018] 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 forced circulation type cooling device using a heat exchanger.

[0019] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples. In the following, flash points were measured using a Cleveland open-type flask in accordance with JIS K2265-4:2007. The weight-average molecular weight and number-average molecular weight were measured by GPC using polystyrene as a standard under the conditions described above.

[0020] Example 1 Activated molecular sieve 4A (15 g), hexamethylcyclotrisiloxane (330 g), and dehydrated tetrahydrofuran (300 g) were charged into a reactor equipped with a thermometer and a stirrer and stirred at 20 to 30°C for 30 minutes. An n-butyllithium-hexane solution (1.6 mol / L, manufactured by Tokyo Chemical Industry Co., Ltd.) (136 g) was added dropwise, and the reaction was carried out at 20 to 40°C for 5 hours. Subsequently, trimethylchlorosilane (38.1 g) and triethylamine (2 g) were added, and the reaction was carried out at 20 to 40°C for 3 hours. The molecular sieve was then separated, and the mixture was heated to 100 to 120°C under reduced pressure to remove the solvent and low-molecular-weight components, yielding an organopolysiloxane (305 g). The resulting organopolysiloxane was represented by the above formula (1), and R １ were all methyl groups, and the average value of n was 8. The organopolysiloxane had a weight average molecular weight (Mw) of 1,600, a molecular weight distribution of 1.07, and a flash point of 180°C. The kinematic viscosity of the polysiloxane at -20°C was 18 mm ２ / s, and the kinematic viscosity at 25°C is 6.3 mm ２ This polysiloxane was used as a refrigerant in a cooling water circulation system (CCA-1112, manufactured by Tokyo Rikakikai Co., Ltd.) having a mechanism for forced circulation of the refrigerant, and was operated at −20°C and 25°C for 30 days (12 hours / day), confirming that it could be used as a refrigerant.

[0021] Example 2 Activated molecular sieve 4A (15 g), hexamethylcyclotrisiloxane (260 g), and dehydrated tetrahydrofuran (220 g) were charged into a reactor equipped with a thermometer and a stirrer and stirred at 20 to 30°C for 30 minutes. A hexane solution of n-butyllithium (1.6 mol / L, manufactured by Tokyo Chemical Industry Co., Ltd.) (62.6 g) was added dropwise, and the reaction was carried out at 20 to 40°C for 5 hours. Subsequently, trimethylchlorosilane (17.5 g) and triethylamine (1 g) were added, and the reaction was carried out at 20 to 40°C for 3 hours. The molecular sieve was then separated, and the mixture was heated to 100 to 120°C under reduced pressure to remove the solvent and low-molecular-weight components, yielding an organopolysiloxane (210 g). The resulting organopolysiloxane was represented by the above formula (1), and R １were all methyl groups, and the average value of n was 30. The organopolysiloxane had a weight average molecular weight (Mw) of 3,800, a molecular weight distribution of 1.08, and a flash point of 260°C. The kinematic viscosity of the polysiloxane at -20°C was 79 mm ２ / s, and the kinematic viscosity at 25°C is 26 mm ２ This polysiloxane was used as a refrigerant in a cooling water circulation system (CCA-1112, manufactured by Tokyo Rikakikai Co., Ltd.) having a mechanism for forced circulation of the refrigerant, and was operated at −20°C and 25°C for 30 days (12 hours / day), confirming that it could be used as a refrigerant.

[0022] Example 3 A reaction vessel was charged with hexamethyldisiloxane (80 g) and decamethylcyclopentasiloxane (1,500 g). Under a nitrogen atmosphere, 97% sulfuric acid (15 g) was added as an acid catalyst and stirred at 25-30°C for 4 hours. Ion-exchanged water (6 g) was then added and stirred at 25-30°C for 30 minutes. The waste acid was then separated and neutralized by washing with water. Low-molecular-weight components were removed at a reduced pressure of 0.5 kPa or less and an internal temperature of 260°C or higher, yielding a colorless, transparent organopolysiloxane (980 g). The resulting organopolysiloxane was a mixture of the above-mentioned formula (1), R １ were all methyl groups, and the average value of n was 46. The organopolysiloxane had a weight average molecular weight (Mw) of 4,800, a molecular weight distribution of 1.14, and a flash point of 290°C. The viscosity of the polysiloxane at -20°C was 113 mm ２ / s, and the viscosity at 25°C is 39 mm ２ This polysiloxane was used as a refrigerant in a cooling water circulation system (CCA-1112, manufactured by Tokyo Rikakikai Co., Ltd.) having a mechanism for forced circulation of the refrigerant, and was operated at −20°C and 25°C for 30 days (12 hours / day), confirming that it could be used as a refrigerant.

[0023] Comparative Example 1 A reaction vessel was charged with hexamethyldisiloxane (180 g) and decamethylcyclopentasiloxane (830 g), reacted in the presence of an acidic catalyst under a nitrogen atmosphere, neutralized by washing with water, and then heated at 100 to 120°C under reduced pressure. Low molecular weight components were removed by stripping, yielding a colorless, transparent dimethylpolysiloxane (820 g). The resulting organopolysiloxane was represented by the above formula (1), and R １ were all methyl groups, and the average value of n was 10. The weight average molecular weight (Mw) was 1,500, the molecular weight distribution was 1.30, and the flash point was 146°C. The kinematic viscosity of the polysiloxane at -20°C was 21 mm ２ / s, and the kinematic viscosity at 25°C is 8.1 mm ２ / s.

[0024] As described above, the linear organopolysiloxane of the present invention is capable of maintaining fluidity at low temperatures and has a high flash point. Therefore, a refrigerant containing this linear organopolysiloxane can be suitably used as a refrigerant in a circulation-type cooling system having a mechanism for forced circulation of the refrigerant.

Claims

1. A refrigerant containing a linear organopolysiloxane represented by the following formula (1): (Here, R １ are each independently an alkyl group having 1 to 4 carbon atoms, and n is an integer of 5 to 80. The linear organopolysiloxane has a weight average molecular weight of 1,000 to 5,000 and a molecular weight distribution [weight average molecular weight (Mw) / number average molecular weight (Mn)] of 1.2 or less.

2. In the above formula (1), R １ The refrigerant of claim 1, wherein is a methyl group or an n-butyl group.

3. The refrigerant according to claim 1, wherein the linear organopolysiloxane has a flash point of 150°C or higher.

4. The linear organopolysiloxane has a flash point of 150°C or higher and a kinematic viscosity of 150mm at -20°C. ２ 10. The refrigerant of claim 1 having a refrigerant mass per square meter (m / s) or less.

5. The refrigerant according to any one of claims 1 to 4, which is a refrigerant for a cooling device.

6. The refrigerant according to claim 5, wherein said cooling device has a mechanism for forced circulation of the refrigerant.

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