The present invention relates to a refrigerant composition for cooling a beverage in a can and a process for producing the same. More specifically, the present invention relates to a refrigerant composition for a self-cooling beverage can (instantly self-cooling can provided with a small cooling chamber (refrigerant capsule) which can cool the beverage in the can by canning, and thus which can does not need to be stored in a refrigerator or a ice box) which comprises paraffin hydrocarbons and olefin hydrocarbons, and to a process for producing said composition.

DESCRIPTION OF THE PRIOR ART It is usual that a refrigerator or other cooling apparatus are used to keep a beverage fresh in a can. In an open field, an ice box is commonly used to enjoy a cool, refreshing beverage.

For a long time, much research has been made to develop a self-cooling can which makes it possible to enjoy a fresh beverage. However, most of the substances which were so far known as a refrigerant capable of cooling a beverage in a can within a very short time appear

to be weak in their cooling effects and to be environmentally unfriendly.

Cooling with an ice box is disadvantageous in that it is inconvenient to carry and handle the ice box because of its bulky volume and heavy weight. Examples of refrigerants which had been applied to put a self-cooling beverage can into commerce include HCFC-22 or HFC-134a (HPC-134a). However, since the global warming potential of the substances is high, they have been classified as an interim alternative substance, i. e., as a restricted substance, under"The Protocol of Montreal". Moreover, HCFC-22 or HFC-134a (HPC-134a) are known as a major causes of environmental damage and thus are not suitable as a refrigerant for a self-cooling beverage can to be consumed in mass.

Generally, a refrigerant for a self-cooling beverage can requires the following properties.

A. Thermodynamic Physical Properties 1) It should evaporate at a low temperature under pressure above atmospheric pressure, and should be easily liquefied at a normal temperature under low pressure.

If the evaporating temperature is low and the refrigerant pressure is lower than an atmospheric pressure, air penetrates the refrigerant receiving chamber installed within the self- cooling beverage can so that the can material is oxidized and rust forms.

In addition, it is preferred that a refrigerant is easily liquefied by water or air and has a low condensing pressure. The reason is that if the condensing pressure of the refrigerant is high, for example, carbonic acid gas, then the refrigerant receiving chamber installed within the self- cooling beverage can should be constructed so as to endure a high interior pressure. Table 1 a below shows the condensing pressures of several refrigerants.

Table la

Refrigerant Condensing Pressure (kg/cm2 abs, 25 ° C) Carbonic Acid Gas 65.69 Ammonia 10.23 HPC-134a 13.96 Methylchloride 5.80 Sulfuric Acid Gas 3.97 Composition of the Present 11.03 Invention 2) It should have a high critical point and should be liquefied at a normal temperature.

A refrigerant should be liquefied even when pressure is added at a temperature above the critical point. A refrigerant gas, such as carbonic acid gas, is not be liquefied even when the temperature of a beverage in the can is slightly higher than the critical temperature of the refrigerant. Then, the self-cooling beverage can does not function. Thus, it is preferred that the refrigerant has a critical temperature above a normal temperature. The refrigerant should be necessarily liquefied within a range of temperatures at which a beverage can is kept. Table lb below shows the critical temperatures of several refrigerants.

Table lb

Refrigerant Critical temperature (25-C) Carbonic Acid Gas 31 Ammonia 133 HPC-134a 101. 15 Methylchloride 143 Sulfuric Acid Gas 157 Composition of the Present 97.8 Invention 3) It should have a low condensing temperature.

If a refrigerant is condensed at a high temperature, then it is impossible to use the refrigerant. Thus, it is preferred that a refrigerant has a low condensing temperature. For instance, the condensing temperature of ammonia is-77.7°C and thus the lowest temperature at which ammonia can be applied as a refrigerant is-70°C. Composition of the present invention has a condensing temperature of-165°C, so it is possible to use it at a temperature of-80°C.

Table 1 c below shows the condensing temperatures of several refrigerants.

Table I e Refrigerant Condensing Temperature(°C) Carbonic Acid Gas-78.51 Ammonia-77.7 HPC-134a-101

Methylchloride-98 Sulfuric Acid Gas-73 Composition of the Present-165 Invention 4) It should have a high heat of vaporization and should have a low liquid specific heat and a low ratio of the liquid specific heat to the heat of vaporization.

If the heat of vaporization of a refrigerant is high, then a small volume of the refrigerant makes it possible to obtain the desired cooling effect. However, if the heat of vaporization of the refrigerant is low, it is necessary to evaporate a large volume of the refrigerant. Table 1 d below shows the heat of vaporization of several refrigerants. Where a liquid specific heat is higher than the heat of vaporization, as the temperature of the liquid is lowered, the refrigerant vapour is generated.

Table Id Refrigerant Heat of Vaporization (Kcal/Kg) Carbonic Acid Gas 62.57 Ammonia 309.64 HPC-134a 42.54 Methylchloride 99.31 Sulfuric Acid Gas 93.60 Composition of the Present 62.35 Invention Then, liquid heat having no cooling ability is passed over a port of the refrigerant receiving chamber installed within the self-cooling can to impede the heat transition action of the refrigerant and also to help reduce the pressure within the port of the chamber.

5) It should have a low viscosity and a low surface tension.

The higher the viscosity, the more increased the flow resistance is. Furthermore, when a refrigerant is passed through the port of a refrigerant receiving chamber installed within a self- cooling beverage can, the flow resistance is increased and as a result the volume efficiency of the port and the cooling ability of the refrigerant are decreased. If the surface tension of a refrigerant is low, the surface of the port can be made smaller by the liquefied refrigerant and thereby a good blowing action takes place when the liquefied refrigerant is passed through the port.

6) The cooling action of a refrigerant should not be effected by an incorporation of water therein.

A refrigerant having an ability to attract water, for example ammonia, may not be effected by water incorporated therein. However, where water is incorporated into a Freon refrigerant which is unable to attract water, the port of a refrigerant receiving chamber installed within a self-cooling can may be frozen and thereby the refrigerant may not be released through the port. Consequently, the cooling action of the refrigerant will be interrupted. Moreover, the Freon refrigerant is hydrolyzed to form an acid followed by generating rust or deposits.

7) It should not affect the can and packing materials.

Where ammonia is applied as a refrigerant, it is appropriate to utilize a packing for the vapour steam which is made by mixing rubber and asbestos since rubber is corroded by ammonia. However, a Freon refrigerant needs a packing to which an unusual rubber is combined. The refrigerant composition of the present invention was developed so as not to affect any currently available materials used for the can and the packing.

8) It should have an appropriate specific gravity and gradient.

Since a high gradient of a refrigerant may affect either the port size or release time, the appropriate specific gravity, molecular weight, and gradient are required for the refrigerant.

B. Chemical Properties 1) It should possess a powerful chemically binding force. It should be chemically stable and should not decompose.

Where a chemically unstable refrigerant is introduced into a refrigerant receiving chamber installed within a self-cooling beverage can, it may be decomposed under pressure, temperature and the like. As a result, the properties of the refrigerant change, so that the pressure of the blowing gas is increased or the cooling action is diminished.

2) It should not corrode metals.

If a refrigerant has the property to corrode metals, the refrigerant receiving chamber may be rusted. The rust formed therefrom may shorten the life of the chamber and deactivate the cooling action of the chamber. The refrigerant composition of the present invention does not

corrode any metals except for magnesium. Thus, it is possible to select any currently available metals as a material for a refrigerant receiving chamber according to the present invention 3) It should be nonflammable and nonexplosive.

If a refrigerant is inflammable and explosive, there are problems when it is used at public buildings, shelters, vessels, vehicles, and the like. For instance, an inflammable and explosive ammonia may be restricted at such places. The refrigerant R-22, nonflammable and nonexplosive, can be used in a mine tunnel 100 metres below the ground but is not environmentally friendly. However, the refrigerant composition of the present invention is environmentally friendly, nonflammable and nonexplosive.

C. Biological Properties 1) It should have an ozone depletion potential of zero (0).

The depletion of the ozone layer results in an increase in an ultraviolet radiation which is harmful to the human body and causes burn damage, eyesight loss, cataract, skin aging, skin cancer, and the like. Furthermore, as the immune system is adversely affected by such ultraviolet radiation, immunity to various cancers, and general resistance of the human body to various causative agents is alleviated. In addition, the occurrence of various diseases such as measles, varicella, herpes, eruption, tuberculosis, and leprosy is increased in line with the increased ultraviolet radiation. Accordingly, a refrigerant must have an ozone depletion potential of zero.

2) It should have a low global warming potential.

A refrigerant should not be classifie as a factor causing for a green house effect which is known to lead to the El Nino phenomenon, extraordinary temperature change, ecosystem destruction, and seawater level rising.

3) It should be harmless to the human body and, when released, should not be detrimental to a self-cooling beverage can.

In most aspects, ammonia is superior to fluorinated halohydrocarbon (HFC) as a refrigerant. Unfortunately, ammonia is inflammable, explosive and has a bad odor. It is gradually being replaced by a Freon refrigerant. As it was recently reporte that the fluorinated halocarbon refrigerant also bears a toxicity, there are problems using it as a refrigerant. It was now found that the refrigerant composition of the present invention does not cause damages to the cooling can when released, and also is harmless to the human body.

4) It should not emit a bad odor.

If a refrigerant has an unpleasant odor, there are some problems when the refrigerant is released through a port. There is still a need to develop an odor-free refrigerant.

SUMMARY OF THE INVENTION The inventors made efforts to develop a new refrigerant which meets with the above requirements, and found that a refrigerant composition comprising (i) at least two components selected from a group consisting of paraffin hydrocarbons such as methane, dimethyl ether, ethane, propane, cyclopropane, n-butane, isobutane, n-pentane and cyclopentane and olefin

hydrocarbons such as ethylene, propylene and butylene, (ii) at least one component selected from a group consisting of methanol and ethanol, and (iii) a heat-stable silicone oil as a flame retardant is effective in cooling a beverage in a self-cooling can which is provided with a refrigerant receiving chamber, and thus enables consumers to conveniently and pleasantly enjoy a canned beverage. The refrigerant composition of the present invention is advantageously nonflammable and thus ensures both excellent cooling effects and safety for a self-cooling can.

It is also environmentally friendly.

BRIEF DESCRIPTION OF THE DRAWING Fig. 1 shows the gas chromatography analysis of the components of the refrigerant composition according to the present invention.

Fig. 2 is a schematically illustrated view of an apparatus which is used to produce the refrigerant composition according to the present invention.

Fig. 3 is a frontal sectional view of a self-cooling beverage can.

DETAILED DESCRIPTION OF THE INVENTION The refrigerant composition for a self-cooling beverage can according to the present invention comprises from 37.0% to 64.9% by weight of at least two components selected from a group consisting of paraffin hydrocarbons such as methane, dimethyl ether, ethane, propane, cyclopropane, n-butane, isobutane, n-pentane and cyclopentane and olefin hydrocarbons such as ethylene, propylene and butylene, from 35.0% to 60.0% by weight of at least one component selected from a group consisting of methanol and ethanol and from 0.1% to 3% by weight of

a heat-stable silicone oil as a flame retardant.

The refrigerant composition of the present invention can be prepared using an apparatus of the present invention with a mixing chamber (10) which is provided with a knitted mesh (20) made from nickel for forming a catalyst layer and a mixer (30) for blending the refrigerant components. The mixer is run by an electric motor (40). Each of the refrigerant components is reserved in tanks (50), respectively. The components in tanks are released through valves (60) and transferred by pump (71), via valve No. 5 (65), to the mixing chamber (10). First, a heat- stable silicone oil is supplied by pump (71) to the mixing chamber (10). Second, one component of methanol, ethanol and a mixture thereof is introduced by pump (71) into the mixing chamber (10) and the resulting mixture is blended by running the electric motor (40). Third, at least two components selected from a group consisting paraffin hydrocarbons (methane, dimethyl ether, ethane, propane, cyclopropane, neobutane, isobutane, neopentane and cyclopentane) and olefin hydrocarbons (ethylene, propylene and butylene) were together supplied by pump (71) to the mixing chamber (10) and the resulting mixture is blended by running the electric motor (40).

The blended composition is released through valve No. 6 (66) and is transferred by pump No.

2 (72) to a cooler (80) in which the composition is cooled and liquefied. Finally, the resulting liquefied composition is released through valve No. 7 (67) to tank (90) for storage.

A pressure indicator (101) is installed behind the supply pump (71) to measure the pressure of the components. The mixing chamber (10) is equipped with a pressure indicator (102), thermometer (110), heater (120) and component level measuring gauge (130). The outside of the mixing chamber (10) is equibbed with a thermowall (111) in which a thermocouple is inserted to measure and regulate the precise reaction temperature by sensor and regulator.

Examples Preparation of the Refrigerant Composition Example 1 Valve No. 1 (61) was opened to permit 1 % by weight of silicone oil reserved in tank No.

1 (51) to be released, via pump No. 1 (71) and valve No. 5 (65), to the mixing chamber (10).

Valve No. 2 (62) was opened to permit 46% by weight of ethanol reserved in tank No. 2 (52) to be released, via pump No. 1 (71) and valve No. 5 (65), to the mixing chamber (10). The electric motor (40) was turned on to blend the components by the mixer (30) for at least two hours. After opening valve No. 3 (63), 33% by weight of cyclopropane stored in tank No. 3 (53) was supplied, via pump No. 1 (71) and valve No. 5 (65), to the mixing chamber (10). The components were again blended by the mixer (30) for at least two hours. Subsequently, valve No. 4 (64) was opened to allow 20% by weight of isobutane stored in tank No. 4 (64) to be supplied, via pump No. 1 (71) and valve No. 5 (65), to the mixing chamber (10). The components were again blended by the mixer (30) for at least two hours. After opening valve No. 6 (66), the resulting composition was transferred by pump No. 2 (72) to the cooler (80).

The composition was then cooled and liquefied in the cooler. The resulting liquefied composition was passed through valve No. 7 (67) and kept in a storage tank (90).

Example 2 A refrigerant composition was prepared in the same manner as in Example 1 except that ethanol, cyclopropanol and isobutanol were used in the amounts of 46.5%, 32% and 20.5% by weight, respectively.

Example 3 A refrigerant composition was prepared in the same manner as in Example 1 except that ethanol, cyclopropanol and isobutanol were used in the amounts of 45%, 36% and 18% by weight, respectively.

Example 4 The refrigerant composition was prepared in the same manner as in Example 1 except that 47% by weight of ethanol and 34% by weight of cyclopropanol were used.

Example 5 The refrigerant composition was prepared in the same manner as in Example 1 except that ethanol, cyclopropanol and isobutanol were used in the amounts of 48%, 26% and 25% by weight, respectively.

The physical properties of the refrigerant compositions according to Examples 1-5 are shown in Tables 2a and 2b below.

Table 2a Refrigerant Example 1 Example 2 Example 3 Example 4 Example 5 Composition I Average 82.24 82.24 82.24 83. 34 82.24 MolecularWeight Specific Gravity (25°) 1.21 1. 21 1. 21 1. 31 1. 21

Boiling Point (°C)-42.98 -42.23 -42.85 43.65 -42.51 -164-164Condensing-165 -165 temperature(°C) Critical Temperature 97.8 97.8 97.1 97.9 97.8 (°C) Critical Pressure 48.9 48.7 48. 3 47.9 48.3 (kg/cm'-) Heat of Vaporization 62.35 61.84 62.11 82.08 63.05 (kcal/kg) Table 2b Refrigerant Example 1 Example 2 Example 3 Example 4 Example 5 Composition ODP(1) 0 0 0 0 0 GWP(2) 3 or less 3 or less 3 or less 3 or less 3 or less Usage Refrigerant Refrigerant Refrigerant Refrigerant Refrigerant Usable-20°C--20°C--20°C--20°C--20°C- Temperature 0°C 0°C 0°C 0°C 0°C SI Temperature (') Flammable Limit(4) Corrosiveness No No No No No (1) Ozone Depletion Potential (2) Global Warming Potential (GWP) is based on CO2 for one hundred years.

(3) The spontaneous inflammation (SI) temperature was determined by the ASTM E659-78 standard in a range of 400° C-700°C (The flask melts at temperatures of more than 700 °C) (4) The flammable limit was determined by the ASTM E681-85 standard within lowest and

highest limits of 0. 3-10% and 10-30%, respectively.

Gaseous organic products were collected from a port by a gas tight syringe and a gas chromatography was conducted to analyse the components of the refrigerant composition of the present invention. The analysis results of the composition in Example 1 according to the present invention were shown in Fig. 1.

The following experiments were carried out to confirm the cooling performance and effects of the refrigerant composition of the present invention. The two self-cooling beverage cans as depicted in Fig. 3 were filled with the refrigerant composition of the present invention.

After 10 days, the refrigerant composition was blown out of the can and the difference between the temperature of the beverage prior to the blowing and the temperature of the beverage after the blowing was measured. The results are shown in Table 3 below in which the compositions in Examples 1 to 5 according to the present invention are compared with R-134a as a control, so far known to have the best cooling performance.

The can (210) is internally provided with a refrigerant (251,252) receiving chamber (221,222). The refrigerant composition of the present invention is contained in the chamber (221,222), and water (241,242) is contained in the can. 170 g of water was contained in each of a cartridge-type can and a cup-type can (210). 80 g and 56 g of the refrigerant composition were contained in the chamber (221,222) within cartridge-type can and cup-type can (210), respectively. The experiments were carried out at normal temperature of 25°C. After the refrigerant composition was completely released out of the vaporizing aperture (230) by canning the beverage within the can, the temperature of the beverage was measured immediately.

Table 3.

Types Temperature of beverage after refrigerant Vaporizing vaporizing Time Theoretical Experimental Difference of (seconds) Temperature Example 1 Cup-4. 3 5. 80 19. 20 175 Cartridge 4.5 7. 80 17. 20 146 Example 2 Cup-4.3 5. 80 19. 20 175 Cartridge 4.5 7. 40 17. 60 146 Example 3 Cup-4. 3 6. 18 18. 82 181 Cartridge 4.5 7. 80 17. 20 141 Example 4 Cup-4. 3 6. 30 18. 70 185 Cartridge 4.5 8. 10 16. 90 147 Example 5 Cup-4.3 6. 30 18. 70 168 Cartridge 4.5 7. 91 17. 09 143 HPC-Cup 4.90 7. 95 17. 05 457 134a (') Cartridge 10.98 15. 91 9. 09 402 (1) HPC-134a was tested five times and the best values thereof were recorded.

Since a beverage in a can is usually at a temperature of 25°C, the refrigerant composition of the present invention can cool the beverage in the can to a temperature of 6 ° C to 9°C. Therefore, it is believed that the refrigerant composition of the present invention makes it possible to put a self-cooling beverage can into commerce.