Fluorine-based solvent composition

Abstract

To provide a novel composition usable in a wide range of applications.SOLUTION: The present invention provides an azeotrope(-like) composition containing perfluoroheptene and chlorotrifluoropropene and a method for cleaning an article using the same.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to azeotropic or azeotrope-like compositions containing a hydrofluoroether and a chlorotrifluoropropene. [Background technology]

[0002] Fluorinated solvents, including halogenated hydrocarbons such as chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), and hydrofluorocarbons (HFCs), have traditionally been used in a wide range of applications in many industries, including as aerosol propellants, refrigerants, solvents, cleaning agents, blowing agents for thermoplastic and thermoset foams, heat transfer media, gaseous dielectrics, fire extinguishing and suppression agents, power cycle working fluids, polymerization media, particulate removal fluids, carrier fluids, buffing compounds, and displacement drying agents.

[0003] However, CFCs and HCFCs are known to be ozone-depleting substances, and HCFCs, particularly HCFC-225, have been widely used due to their non-flammability, polymer compatibility, and stability. However, HCFCs have an ozone-depleting potential and a high global warming potential, so they were completely phased out in 2019. On the other hand, although HFCs do not pose a risk to the ozone layer, they do contribute to global warming as greenhouse gases, and therefore there is a demand for alternatives that have a lower environmental impact, i.e., zero ozone depletion potential and very low global warming potential.

[0004] Hydrochlorofluoroolefins (HCFOs), hydrofluoroolefins (HFOs), perfluoroolefins (PFOs) and hydrofluoroethers (HFEs) have been developed as such replacements. Of these, HCFO is excellent at removing oil, but it is known to have the problem of being highly polymer-attacking (causing cloudiness, cracking, dissolution, etc. of polymers), making it unsuitable for use as a cleaning agent in many products that contain polymers. On the other hand, HFEs such as 1,2,2,2-tetrafluoroethyl-heptafluoropropyl ether, 1,1,1,2,3,3-hexafluoro-2-heptafluoropropyloxy-3-(1,2,2,2-tetrafluoroethoxy)-propane, heptafluoropropyl methyl ether, ethyl-1,1,2,2-tetrafluoroethyl ether, methyl nonafluorobutyl ether, and ethyl nonafluorobutyl ether have zero ozone depletion potential, low global warming potential, and low polymer attack, and therefore have been proposed for use as solvents.

[0005] Furthermore, when used as a cleaning agent or the like, it is known that an azeotropic composition that does not fractionate during use or distillation during recovery, i.e., that has a constant boiling point property and does not fractionate during boiling or evaporation, is useful (e.g., Patent Document 3, Patent Document 4, and Patent Document 5). However, as also described in Patent Document 1, it is impossible to theoretically predict whether an azeotropic composition will be formed, and a search is ongoing for new azeotropic compositions with excellent properties for various combinations. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-110035 [Patent Document 2] International Publication No. 2019 / 213193 [Patent Document 3] Special Publication No. 6-501949 [Patent Document 4] Special Publication No. 2013-514444 [Patent Document 5] Special Publication No. 2012-528922 [Patent Document 6] International Publication No. 2018 / 092780 [Patent Document 7] Japanese Patent Application Publication No. 10-036894 [Patent Document 8] Japanese Patent Application Laid-Open No. 2002-256295 Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide a novel azeotropic or azeotrope-like composition that can solve the above problems and can be used in a wide range of industrial applications. [Means for solving the problem]

[0008] The present inventors have discovered that a composition containing a hydrofluoroether (HFE), which has an ozone depletion potential of 0 and a low global warming potential, and a chlorotrifluoropropene, which has excellent oil-removing properties, is highly safe and environmentally friendly, has excellent polymer compatibility (has reduced polymer attack), and forms an azeotropic composition or an azeotrope-like composition that behaves similarly to a single compound, thereby completing the present invention.

[0009] That is, the present invention is characterized by the following points. 1. An azeotropic or azeotrope-like composition containing a hydrofluoroether and a chlorotrifluoropropene, wherein the temperature difference between the vapor phase temperature and the liquid phase temperature is within 2°C. 2. The azeotropic or azeotrope-like composition according to 1 above, which is a cleaning composition. 3. The azeotropic or azeotrope-like composition according to 1. or 2. above, wherein the hydrofluoroether is at least one selected from methyl nonafluorobutyl ether, ethyl nonafluorobutyl ether, 2,2,2-trifluoroethyl-1,1,2,2-tetrafluoroethyl ether, and isomers thereof. 4. The azeotropic or azeotrope-like composition according to 1. or 2. above, wherein the chlorotrifluoropropene is at least one selected from 1-chloro-2,3,3-trifluoro-1-propene, 1-chloro-3,3,3-trifluoro-1-propene, and isomers thereof. 5. The azeotrope or azeotrope-like composition according to any one of 1. to 4. above, which consists of 0.1 to 83.0 mass % of methyl nonafluorobutyl ether and 17.0 to 99.9 mass % of 1-chloro-2,3,3-trifluoro-1-propene. 6. The azeotropic or azeotrope-like composition according to any one of 1. to 4. above, which consists of 0.1 to 40.5 mass % of methyl nonafluorobutyl ether and 59.5 to 99.9 mass % of 1-chloro-3,3,3-trifluoro-1-propene. 7. The azeotropic composition or azeotrope-like composition according to any one of 1. to 4. above, which consists of 0.1 to 35.0 mass % of ethyl nonafluorobutyl ether and 65.0 to 99.9 mass % of 1-chloro-2,3,3-trifluoro-1-propene. 8. The azeotrope or azeotrope-like composition according to any one of 1. to 4. above, which consists of 0.1 to 99.9 mass % of 2,2,2-trifluoroethyl-1,1,2,2-tetrafluoroethyl ether and 0.1 to 99.9 mass % of 1-chloro-2,3,3-trifluoro-1-propene. 9. A method for cleaning an article using the azeotropic composition or azeotrope-like composition described in any one of 1. to 8. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a composition that has an ozone depletion potential of zero and a very low global warming potential. The azeotropic or azeotrope-like composition of the present invention has excellent oil removal properties with hydrofluoroether. The present invention also has the advantage that the azeotropic or azeotrope-like composition behaves similarly to a single compound and is non-flammable. [Brief explanation of the drawings]

[0011] [Figure 1] 1 shows the vapor-liquid equilibrium curve of Example 1. [Figure 2]1 shows a vapor-liquid equilibrium curve of Example 2. [Figure 3] The vapor-liquid equilibrium curve of Example 3 is shown. [Figure 4] 1 shows the vapor-liquid equilibrium curve of Example 4. [Figure 5] 1 shows the vapor-liquid equilibrium curve of Example 5. [Figure 6] 1 shows the vapor-liquid equilibrium curve of Example 6. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention will be described in detail below. The azeotropic composition or azeotrope-like composition of the present invention consists essentially of a hydrofluoroether (HFE) and chlorotrifluoropropene (HCFO-1233), and the combined amount of both components preferably accounts for 50% by mass or more, desirably 55% by mass or more, and more desirably 60% by mass or more of the composition.

[0013] In the present invention, the structural isomer or stereoisomer of HFE, which is one of the components, is not particularly limited, and may be a single isomer or a mixture of isomers. Preferably, HFE is at least one selected from methyl nonafluorobutyl ether, ethyl nonafluorobutyl ether, 2,2,2-trifluoroethyl-1,1,2,2-tetrafluoroethyl ether, and isomers thereof.

[0014] Regarding the other component, HCFO-1233, various isomers are known to exist, but the HCFO-1233 used in the present invention is not particularly limited in terms of its structural isomers or stereoisomers. The HCFO-1233 used may be a single isomer or a mixture of isomers. Specifically, 1-chloro-2,3,3-trifluoro-1-propene (HCFO-1233yd), 1-chloro-3,3,3-trifluoro-1-propene (HCFO-1233zd), or a mixture thereof is preferred. Furthermore, HCFO-1233yd is preferably cis-HCFO-1233yd or a mixture containing cis-HCFO-1233yd.

[0015] As recognized in the art, an azeotropic composition is a mixture of two or more distinct components which, when in liquid form at a given pressure, boils at a substantially constant temperature, which is either above or below the boiling temperatures of the individual components, and which provides a vapor composition that is essentially the same as the overall liquid composition during boiling (see, e.g., M.F. Doherty and (See MFMalone, Conceptual Design of Distillation Systems, McGraw-Hill (New York), 2001, pp. 185-186, 351-359).

[0016] When the composition of the mixed liquid is varied and the vapor-liquid equilibrium relationship at constant pressure is measured, it is known that the boiling point of the mixture will be either maximum or minimum in a composition that forms an azeotropic composition.

[0017] Thus, the essential characteristics of an azeotropic composition are that, at a given pressure, the boiling point of the liquid composition is fixed, and the composition in the vapor phase of the composition during boiling is essentially the composition in the liquid phase during boiling (i.e., no fractionation of the components of the liquid composition occurs). When an azeotropic composition is subjected to boiling at different pressures, both the boiling point and the mass percentage of each component of the azeotropic composition change. It is also recognized in the art that azeotropic compositions may vary. Thus, azeotropic compositions may be defined in terms of a unique relationship that exists between the components, or in terms of a compositional range of the components, or in terms of the exact mass percentage of each component of a composition characterized by a fixed boiling point at a specified pressure.

[0018] The "azeotrope-like composition" of the present invention is a composition that behaves like an azeotrope (i.e., has constant boiling point properties or a tendency not to fractionate upon boiling or evaporation), meaning that the liquid and vapor phase compositions are as close as possible and are unlikely to change over time. Preferably, the difference between the liquid and vapor phase temperatures at a given pressure on the vapor-liquid equilibrium curve is 2°C or less, more preferably 1°C or less, and even more preferably 0.5°C or less. This is in contrast to non-azeotrope-like compositions, which undergo a significant change in vapor-liquid composition during boiling or evaporation.

[0019] The azeotropic or azeotrope-like composition of the present invention containing a hydrofluoroether and chlorotrifluoropropene desirably has a boiling point under atmospheric pressure in the range of 30 to 100°C, preferably 35 to 100°C, and more preferably 40 to 80°C.

[0020] In the present invention, when the chlorotrifluoropropene is 1-chloro-2,3,3-trifluoro-1-propene (HCFO-1233yd), the boiling point of the azeotropic composition or azeotrope-like composition of the present invention under atmospheric pressure is preferably 50 to 58°C, more preferably 51 to 58°C. The relative amounts of hydrofluoroethers are preferably methyl nonafluorobutyl ether:HCFO-1233yd=0.1-83.0:17.0-99.9% by mass, more preferably 2.0-80.0:20.0-98.0% by mass, ethyl nonafluorobutyl ether:HCFO-1233yd=0.1-35.0:65.0-99.9% by mass, more preferably 0.1-30.0:70.0-99.9% by mass, and 2,2,2-trifluoroethyl-1,1,2,2-tetrafluoroethyl ether:HCFO-1233yd=0.1-99.9:0.1-99.9% by mass, more preferably 1.0-99.0:1.0-99.0% by mass. If the HFE is less than 5.0 mass% (i.e., if the amount of HCFO is too large relative to the HFE), polymer attack may increase, and conversely, if the HFE is more than 95.0 mass% (i.e., if the amount of HCFO is too small relative to the HFE), the oil removal rate may decrease.

[0021] In the present invention, when the chlorotrifluoropropene is 1-chloro-3,3,3-trifluoropropene (HCFO-1233zd), the boiling point of the azeotropic composition or azeotrope-like composition of the present invention under atmospheric pressure is preferably 38 to 46°C, more preferably 39 to 45°C. When the chlorotrifluoropropene is 1-chloro-3,3,3-trifluoro-1-propene (HCFO-1233zd), the blending ratios of hydrofluoroethers are preferably methyl nonafluorobutyl ether:HCFO-1233zd=0.1-40.5:59.5-99.9% by mass, more preferably 0.1-35.0:65.0-99.9% by mass, ethyl nonafluorobutyl ether:HCFO-1233zd=0.1-11.0:89.0-99.9% by mass, and 2,2,2-trifluoroethyl-1,1,2,2-tetrafluoroethyl ether:HCFO-1233zd=0.1-38.0:62.0-99.9% by mass. Regarding the blending amount, if the HFE is less than 10.0 mass % (i.e., if the amount of HCFO is too large relative to the HFE), polymer attack may increase. Conversely, if the HFE is more than 75.0 mass % (i.e., if the amount of HCFO is too small relative to the HFE), ), a decrease in oil removal rate may occur.

[0022] The azeotropic composition or azeotrope-like composition of the present invention may optionally contain one or more stabilizers selected from the group consisting of nitroalkanes, epoxides, furans, benzotriazoles, phenols, amines, and phosphates, and the amount of the stabilizer added is 0.01 to 5.00% by mass, preferably 0.05 to 0.50% by mass, based on the total mass of the composition.

[0023] The azeotropic composition or azeotrope-like composition of the present invention may also contain other components, such as alcohols, ketones, ethers, esters, hydrocarbons, amines, glycol ethers, and siloxanes, as necessary, as long as the features of the present invention are not impaired.

[0024] The azeotropic or azeotrope-like composition of the present invention has an ozone depletion potential (ODP) of 0 and a global warming potential (GWP) of about 100 or less, preferably 50 or less, and more preferably 10 or less. Here, the ODP and GWP in the present invention are defined in the World Meteorological Organization report "Scientific Assessment of Ozone Depletion, 2002."

[0025] The azeotropic or azeotrope-like compositions of the present invention can be used in a wide range of applications where halogenated hydrocarbons have traditionally been used, such as aerosol propellants, refrigerants, solvents, cleaning agents, particulate removal fluids, blowing agents (foam expansion agents) for thermoplastic and thermoset foams, heat transfer media, gaseous dielectrics, fire extinguishing and suppression agents, power cycle working fluids, polymerization media, carrier fluids, buffing agents, and displacement drying agents.

[0026] When the present invention is used as a cleaning agent, the objects to be cleaned with the azeotropic composition or azeotrope-like composition of the present invention are not particularly limited. However, the composition can be suitably used for electronic, electrical, and machine parts, small automobile parts, and other items that need to be continuously produced and cleaned. In particular, the azeotropic composition or azeotrope-like composition of the present invention can be suitably used as a cleaning agent for cleaning solid surfaces having organic (oil) or inorganic contaminants on their surfaces, such as semiconductor surfaces, electronic substrate surfaces, electronic circuits, CMOS (Complementary Metal Oxide Semiconductors), MEMS (Micro Electro Mechanical Systems), hard disk surfaces, and other surfaces with fine structures.

[0027] In particular, the azeotropic composition or azeotrope-like composition of the present invention is highly safe and environmentally friendly, has excellent polymer compatibility (polymer attack is suppressed), has high oil removal properties and excellent cleaning properties, and forms an azeotropic composition or azeotrope-like composition that behaves similarly to a single compound, making it suitable for cleaning resin products.

[0028] The azeotropic or azeotrope-like composition of the present invention can also be suitably used as a refrigerant for cooling. In particular, since it exhibits azeotropy, it is also suitable as a refrigerant for use in a cooling method (boiling cooling) that includes a step of condensing the composition of the present invention and a step of evaporating it near an object to be cooled.

[0029] Furthermore, the azeotrope or azeotrope-like compositions of the present invention can be suitably used as blowing agents (foam expanding agents) for producing thermoplastic or thermoset foams. The present invention will be described in detail below with reference to examples. [Example]

[0030] A mixture of HFE and HCFO-1233yd or HCFO-1233zd The boiling point, surface tension, density, viscosity, and flash point of each of the above-mentioned compositions were measured and calculated, and an oil removal test and a resin compatibility test were carried out by the following methods.

[0031] [Boiling point (equilibrium reflux boiling point)] The boiling point (equilibrium reflux boiling point) was measured in accordance with JIS K 2233, except that the cooling water temperature was set to 5°C and heating was performed directly without any interposition between the hot plate and the flask.

[0032] Density: Amager's Law V m =Σx j V j V: Density x: mole fraction The density values ​​of the HFEs used were 1.52 g / ml for methyl nonafluorobutyl ether, 1.43 g / ml for ethyl nonafluorobutyl ether, and 1.47 g / ml for 2,2,2-trifluoroethyl-1,1,2,2-tetrafluoroethyl ether (manufacturer published values, set at 25°C). The density of HCFO-1233yd was 1.39 g / ml (quoted from AGC Research Report 69 (2019) "Development of Environmentally Friendly Fluorinated Solvent AMOLEA (registered trademark) AS-300"), and the density of HCFO-1233zd was 1.31 g / ml (quoted from Central Glass Co., Ltd., 1233Z, Excellent Environmental Performance, High Detergency, Next-Generation Fluorinated Solvent, October 2015).

[0033] The viscosity of the composition was calculated using the following formula. Viscosity: McAllister's method lnη m =Σx i f(η i ) η: Viscosity x: mole fraction f(η): logarithm of viscosity The viscosities of the HFEs used were 0.58 mPa·s for methyl nonafluorobutyl ether, 0.57 mPa·s for ethyl nonafluorobutyl ether, and 0.65 mPa·s for 2,2,2-trifluoroethyl-1,1,2,2-tetrafluoroethyl ether (manufacturer-published values, set at 25°C). The viscosity of HCFO-1233yd was 0.57 mPa·s (quoted from AGC Research Report 69 (2019) "Development of Environmentally Friendly Fluorinated Solvent AMOLEA® AS-300"), and the viscosity of HCFO-1233zd was 0.41 mPa·s (quoted from Central Glass Co., Ltd., 1233Z, Excellent Environmental Performance, High Detergency, Next-Generation Fluorinated Solvent, October 2015).

[0034] [surface tension] The surface tension of the composition was calculated using the following formula. Surface tension: Macleod-Sugden correlation σ 1 / 4 =[P](ρ L -ρ V ) / MW σ; surface tension P: Parachor coefficient ρ L :Liquid specific gravity ρ v :Vapor specific gravity, MW: molecular weight The surface tension values ​​of HFE are 13.6 mN / m for methyl nonafluorobutyl ether, 13.6 mN / m for ethyl nonafluorobutyl ether, and 16.4 mN / m for 2,2,2-trifluoroethyl-1,1,2,2-tetrafluoroethyl ether (manufacturer published values, set at 25°C). The surface tension of HCFO-1233yd is 21.7 mN / m (quoted from AGC Research Report 69 (2019) Development of Environmentally Friendly Fluorinated Solvent AMOLEA (registered trademark) AS-300), and the surface tension of HCFO-1233zd is 1 8.6 mN / m (quoted from Central Glass Co., Ltd., 1233Z, Excellent environmental performance, high cleaning power, next generation fluorine-based solvent, October 2015).

[0035] [flash point] The flash point was measured by the Tag closed cup and Cleveland open cup flash point tests in accordance with JIS K 2265-1980.

[0036] [Oil removal rate] The oil removal rate is used as an index of cleaning performance and was calculated using the following formula:

number

[0037] [Cleaning conditions] The cleaning agent used was the composition shown in Table 1. As the equipment, a tabletop ultrasonic cleaner (three-frequency ultrasonic cleaner VS-100III type) was used, and cleaning was performed at an ultrasonic frequency of 28 kHz, an output of 100 W, a cleaning time of 3 minutes, and room temperature.

[0038] [Resin compatibility test (Polycarbonate (PC))] A test piece (2×20×100 mm) made of PC resin was immersed in the composition shown in Table 1 at room temperature for 15 minutes, and the weight change and hardness change were measured.

[0039] The HFE, HCFO-1233yd, and HCFO-1233zd used in the examples and comparative examples are as follows: HFE Methyl Nonafluorobutyl Ether (3M (registered trademark), Novec (registered trademark) 7100) Ethyl Nonafluorobutyl Ether (3M (registered trademark), Novec (registered trademark) 7200) 2,2,2-trifluoroethyl-1,1,2,2-tetrafluoroethyl ether (AGC (registered trademark), Asahiklin (registered trademark) AE3000) HFO-1233 HCFO-1233yd (AGC (registered trademark) AMOLEA (registered trademark) AS-300) HCFO-1233zd (Central Glass (registered trademark), Serefine (registered trademark) 1233Z) The oils and resins used in the examples and comparative examples are as follows: ·Oils Silicone oil (Shin-Etsu Chemical Co., Ltd., KF-96-100) ·Resins PC resin (Standard Test Piece)

[0040] [Examples 1 to 6, Comparative Examples 1 to 5] The boiling points, surface tensions, densities, viscosities, and flash points of the compositions of the present invention, as well as HFE, HCFO-1233yd, and HCFO-1233zd, are shown in Table 1. The oil removal rates of Examples 1 to 6 and Comparative Examples 1 to 3, as well as the results of the PC resin compatibility test, are also shown in Table 1. The vapor-liquid equilibrium curves of Examples 1 to 6 are shown in Figures 1 to 6, respectively. The liquidus and dashed lines indicate the vapor line. Except for Figure 3, the squared temperatures in the figures are the maximum values ​​of the composition range for each composition (the larger value of the composition percentages in the squared boxes in the figures), and are the temperatures indicated by the liquidus and vapor line. In Figure 3, the squared temperatures are the temperatures at the composition with the largest difference between the vapor line and the liquidus line (83.0% by mass of 2,2,2-trifluoroethyl-1,1,2,2-tetrafluoroethyl ether).

[0041] In FIG. 1, it was confirmed that when the mass ratio of methyl nonafluorobutyl ether / HCFO-1233yd was 45 / 55, an azeotrope with a minimum boiling point of 51°C was formed, and that in the range of 0.1 / 99.9 to 83.0 / 17.0, an azeotropic state was observed, with the temperature difference between the vapor phase and liquid phase being within 2°C. In Figure 2, it was confirmed that when the mass ratio of ethyl nonafluorobutyl ether / HCFO-1233yd was in the range of 2.8 / 97.2 to 11.5 / 88.5, an azeotropy with a minimum boiling point of 54.9°C was observed, and when the mass ratio was in the range of 0.1 / 99.9 to 35.0 / 65.0, an azeotropic-like state was observed, and the temperature difference between the vapor phase and liquid phase was within 2°C. In FIG. 3, it was confirmed that when the mass ratio of 2,2,2-trifluoroethyl-1,1,2,2-tetrafluoroethyl ether / HCFO-1233yd was 45 / 55, an azeotropic mixture with a minimum boiling point of 53°C was formed, and when the mass ratio was in the range of 0.1 / 99.9 to 99.9 / 0.1, an azeotropic state was formed, and the temperature difference between the vapor phase and liquid phase was within 2°C.

[0042] In FIG. 4, it was confirmed that an azeotropic state was observed when the mass ratio of methyl nonafluorobutyl ether / HCFO-1233zd was in the range of 0.1 / 99.9 to 40.5 / 59.5, and the temperature difference between the vapor phase and liquid phase was within 2°C. In FIG. 5, it was confirmed that an azeotropic state was observed when the mass ratio of ethyl nonafluorobutyl ether / HCFO-1233zd was in the range of 0.1 / 99.9 to 11.0 / 89.0, and the temperature difference between the vapor phase and liquid phase was within 2°C. In FIG. 6, it was confirmed that an azeotropic state was observed when the mass ratio of 2,2,2-trifluoroethyl-1,1,2,2-tetrafluoroethyl ether / HCFO-1233zd was in the range of 0.1 / 99.9 to 38.0 / 62.0, and the temperature difference between the vapor phase and liquid phase was within 2°C.

[0043] Furthermore, in Table 1, polymer attack (significant change in hardness of polycarbonate resin) was observed in Comparative Example 4, but suppression of polymer attack (change in hardness) was observed in Examples 1 to 6. As shown in Table 1, the compositions of the examples exhibit an excellent oil removal rate, high detergency, and very low polymer attack.

[0044] [Table 1]

Claims

1. An azeotropic or azeotrope-like composition containing ethyl nonafluorobutyl ether and 1-chloro-3,3,3-trifluoro-1-propene, wherein the temperature difference between the vapor phase temperature and the liquid phase temperature is within 2°C.

2. 10. The azeotrope or azeotrope-like composition of claim 1, which is a cleaning composition.

3. The azeotrope or azeotrope-like composition of claim 1, comprising 0.1 to 11.0% by mass of ethyl nonafluorobutyl ether and 89.0 to 99.9% by mass of 1-chloro-3,3,3-trifluoro-1-propene.

4. A method for cleaning an article using the azeotropic or azeotrope-like composition of any one of claims 1 to 3.

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