WO1995025775A1

WO1995025775A1 - Cooling compositions

Info

Publication number: WO1995025775A1
Application number: PCT/GB1995/000556
Authority: WO
Inventors: Timothy James Noakes; Maurice Joseph Prendergast
Original assignee: Imperial Chemical Industries Ltd
Current assignee: Imperial Chemical Industries Ltd
Priority date: 1994-03-22
Filing date: 1995-03-15
Publication date: 1995-09-28
Anticipated expiration: 1996-09-22
Also published as: GB9405594D0

Abstract

A cooling composition comprising at least one fluorine-containing compound having a boiling point below 0 °C selected from the (hydro)fluorocarbons and the (hydro)fluorocarbon ethers and at least one surface active agent is described. A method for cooling an article using the composition and a spray device containing the composition is also described.

Description

COOLING COMPOSITIONS

The present invention relates to cooling compositions which are delivered from a spray device for the direct cooling of an article such as an electronic component.

The rapid cooling of articles such as electronic components using a low boiling point fluid delivered from a spray device is known in the art. The low boiling point fluid is usually delivered by means of an aerosol and the aerosol product containing the fluid is often called a freezer spray or a freezer aerosol. In the electronics industry, these freezer sprays are used to cool electronic components so as to locate faults, assess low temperature performance or to prevent damage during soldering. Hitherto, various chlorofluorocarbons such as dichlorodifluoromethane (R-12) have found widespread use as the low boiling point fluid in these freezer sprays.

However, the chlorofluorocarbons such as dichlorodifluoromethane have been implicated in the destruction of the earth's protective ozone layer, and there is general agreement that their manufacture and use should be severely restricted and eventually phased out completely. It is important, therefore, to replace the chlorofluorocarbons with materials having low or zero ozone depletion potentials.

The use of certain hydrofluorocarbons in place of the chlorofluorocarbons has been proposed in the refrigeration industry. Thus, refrigerant R-12 is generally being replaced by a new refrigerant, 1,1,1,2-tetrafluoroethane (R-134a). However, R-134a cannot be satisfactorily used as a direct substitute for R-12 in freezer spray applications since it tends to result in the generation of large quantities of electrostatic charge on the surface of the article being sprayed. This build-up of electrostatic charge will not only damage delicate electronic components but is also unsafe.

The present applicants have investigated this problem and have developed a cooling composition comprising a low boiling point fluid having a low or zero ozone depletion potential which does not lead to the generation of excessive amounts of electrostatic charge.

According to the present invention there is provided a cooling composition comprising at least one fluorine containing compound having a boiling point below 0°C selected from the (hydro)fluorocarbons and (hydro)fluorocarbon ethers and at least one surface active agent.

The present invention also provides a process for cooling an article which comprises contacting that article with a cooling composition comprising at least one fluorine containing compound having a boiling point below 0°C selected from the (hydro)fluorocarbons and (hydro)fluorocarbon ethers and at least one surface active agent.

The cooling composition of the invention will usually be delivered from a spray device by means of pressure acting on the composition and will normally be delivered as a liquid.

Accordingly, the present invention also provides a spray device for delivering a composition under the action of pressure comprising a spray head and a container holding the composition to be delivered from the spray head characterised in that the said composition is a cooling composition comprising at least one fluorine containing compound having a boiling point below 0°C selected from the (hydro)fluorocarbons and (hydro)fluorocarbon ethers and at least one surface active agent.

Suitable spray devices include aerosols in which the cooling composition is stored under pressure in a container with the at least one fluorine containing compound not only functioning as the cooling fluid but also as the propellant by creating the pressure necessary to drive the cooling composition from the container.

In this specification, a (hydro)fluorocarbon is a compound selected from the group consisting of the hydrofluorocarbons and the perfluorocarbons, and a (hydro)fluorocarbon ether is a compound selected from the group consisting of the hydrofluorocarbon ethers and the perfluorocarbon ethers. The cooling composition may contain a mixture of two or more fluorine containing compounds, including a mixture containing a (hydro)fluorocarbon and a (hydro)fluorocarbon ether.

The (hydro)fluorocarbons and/or (hydro)fluorocarbon ethers which are used in the cooling compositions of the present invention will preferably have a boiling point below -10"C, more preferably below -15°C and particularly preferably below -20°C.

The preferred cooling compositions comprise one or more fluorine containing compounds selected from the hydrofluorocarbons and the hydrofluorocarbon ethers, and of these cooling compositions comprising one or more hydrofluorocarbons are particularly preferred.

Suitable hydrofluorocarbon ethers may be selected from the group consisting of trifluoromethyl difluoromethyl ether (CF.OCF H), pentafluoroethyl difluoromethyl ether (CF.CF_OCF_H) , 1,1,1,2-tetrafluoroethyl trifluoromethyl ether (CF CFHOCF ) and trifluoromethyl fluoromethyl ether (CF,OCFH_).

The preferred hydrofluorocarbons for use in the cooling compositions of the invention are selected from the C. , hydrofluorocarbons and particularly the C hydrofluoroalkanes. Examples of C _ hydrofluoroalkanes which may be used in the cooling compositions of the present invention include, inter alia, trifluoromethane, fluoromethane, difluoromethane, pentafluoroethane, 1,1,1-trifluoroethane, 1, 1,2,2-tetrafluoroethane,

1,1,1,2-tetrafluoroethane and 1, 1,1,3,3,3-hexafluoropropane. Cooling compositions comprising one or more hydrofluoroethanes form a particularly preferred embodiment of the present invention, and of these cooling compositions comprising 1,1,1,2-tetrafluoroethane (R-134a) are especially preferred.

The surface active agent, which also forms an essential component of the cooling compositions of the present invention, may be of the anionic, cationic, nonionic or amphoteric variety and may be selected from any of the surface active agents known in the art. Liquid surface active agents are preferred to solid surface active agents since solid materials may leave undesirable deposits on the surface of the article being sprayed. Additionally, of the four classes of surface active agents listed above, nonionic and especially cationic surface active agents have been found to be particularly effective in that only very small concentrations of these materials are needed in the cooling composition to adequately suppress the accumulation of electrostatic charge on the surface of the article being sprayed. Accordingly, the preferred cooling compositions comprise one or more nonionic and/or cationic surface active agents, and of these cooling compositions comprising one or more cationic surface active agents are particularly preferred. Mixtures of two or more surface active agents may be used if desired including mixtures comprising more than one class of surface active agent .

Suitable nonionic surface active agents include the polyethers. These materials, which are also known as alkoxylates, have a polyether chain which contains repeating units derived from an alkylene oxide, typically ethylene and/or propylene oxide.

The preferred cationic surface active agents for use in the cooling compositions of the invention are the quaternary ammonium salts since these materials have been found to be capable of providing the required suppression of electrostatic charge at extremely low concentrations in the cooling composition. Quaternary ammonium salts, as a class of surface active agents, are well known to those versed in the art. They typically contain a long chain aliphatic hydrocarbon group, such as a long chain alkyl group, and a selection of other organic moieties and possibly hydrogen bonded to the ammonium N atom. There will, of course, be a positive charge associated with the ammonium grouping, and so quaternary ammonium salts will also contain a salt forming counterion which will bring with it an associated negative charge. The long chain aliphatic hydrocarbon group will tend to be linear but may contain a degree of branching and will typically contain from 10 to 20 carbon atoms. A given material may, of course, contain both linear and branched hydrocarbon groups. Thus, a typical quaternary ammonium salt surface active agent will contain one or more compounds having the formula:

wherein

R is a linear or branched long chain aliphatic hydrocarbon group, particularly a linear or branched long chain alkyl group and especially a linear or branched C_ιn_„_n alkyl group; each of X, Y and Z are independently H or an organic moiety, particularly a short chain alkyl group or an alkoxylate group; and

A is a counterion.

As indicated above, each of X, Y and Z are preferably independently selected from the short chain alkyl groups and the alkoxylate groups containing repeating units derived from one or more alkylene oxides. Preferred short chain alkyl groups are the C, . alkyl groups, with methyl being an especially preferred short chain alkyl group. Preferred alkoxylate groups are selected from the ethoxylates, the propoxylates and the ethoxylates-propoxylates which contain repeating units derived from one or both of ethylene oxide and propylene oxide. The alkoxylate chain will typically contain from 1 to 100 and more typically from 1 to 50 repeating units derived from the alkylene oxide.

The preferred counterions for A are the halide ions, especially bromide and chloride, and the methosulphate (CH.SO.) and ethosulphate (CH CH_?SO.) ions. The methosulphate and ethosulphate ions are particularly preferred on account of their low corrosivity.

Although the present cooling compositions may contain as much as 1.0 % by weight of the surface active agent, or even more, very small quantities of the surface active agent, e.g. of the order of 0.1 to 10,000 ppm (parts per million) by weight, have been found to be satisfactory in terms of providing a cooling composition which does not generate excessive amounts of electrostatic charge on the surface of the article on which it is being sprayed. This is clearly advantageous, since the problem of residual surface active agent remaining on the surface of the article can be much reduced or even eliminated. Typically, the cooling composition will contain from 0.1 to 5,000 ppm, preferably from 0.1 to 2,000 ppm, more preferably from 0.1 to 1,000 ppm and particularly preferably from 0.1 to 500 ppm of the surface active agent on a weight basis. Especially preferred cooling compositions contain less than 100 ppm by weight of the surface active agent.

The cooling composition may also contain a solubilising agent to aid the dissolution of the surface active agent in the one or more fluorine containing compounds constituting the cooling fluid. Suitable solubilising agents may be selected from the alcohols, particularly the C, alkanols, with ethanol being especially preferred. If a solubilising agent is employed in the cooling composition, it will usually be present in an amount of from 0.001 to 10.0 % by weight, preferably in an amount of from 0.001 to 1.0 % by weight on the total weight of the composition.

The present invention is now illustrated but not limited by the following examples. The cooling compositions tested were delivered using a spray device fitted with an aerosol valve.

Examples 1 to 5

In these examples, the performance of a series of cooling compositions comprising 1,1,1,2-tetrafluoroethane (R-134a) and varying amounts of Decon Neutracon (a product available from Decon Laboratories Ltd containing a blend of anionic and nonionic surface active agents) was investigated.

The surface active agent was dissolved in ethanol (a solubilising agent) to give a 10 % v/v solution, i.e. a solution containing 10 % by volume of the surface active agent and 90 % by volume of the ethanol. A certain volume of this solution, which was different for each example so as to vary the amount of the surface active agent in the cooling composition, was then charged to the spray device followed by about 40 g of the R-134a.

The various cooling compositions were then subjected to an electrostatic spray test as follows:

The electrostatic test rig comprised a stainless steel target disc which was electrically insulated and connected to an electrostatic voltmeter for recording the electrostatic charge generated on the surface of the disc as a result of the spraying operation. The spray device containing the cooling composition to be tested was held about 5 cm away from the stainless steel target disc and the cooling composition, which formed a liquid jet, aimed at the centre of the disc. Spraying was continued for 5 seconds. The charge generated on the surface of the disc as a result of the spraying was monitored by the electrostatic voltmeter and the maximum charge displayed on the digital read-out was recorded.

A control experiment was also conducted using neat R-134a as the cooling fluid. The neat R-134a was charged to an identical spray device and the electrostatic spray test was carried out using the same technique as described above.

The results of the electrostatic spray tests (in kilovolts (kV)) are shown in Table 1 together with the amounts of the surface active agent/ethanol solution and the amounts of the surface active agent contained in the cooling compositions of Examples 1 to 5.

TABLE 1

Examp1e Amount of solution (*) Amount of Electro¬ in cooling composition SAA (*) in static

(% by weight) cooling spray composition test (kV)

(ppm by weight)

1 2.0 2,000 0

2 1.0 1,000 0.02

3 0.1 100 0.1

4 0.05 50 0.15

5 0.01 10 1.8

Control 0 0 29.0

(*) In Table 1 above, the reference to solution means the solution of the surface active agent in the ethanol and SAA means surface active agent.

Examples 6 to 10

In these examples, the performance of a series of cooling compositions comprising 1,1,1,2-tetrafluoroethane (R-134a) and varying amounts of Synprolam (TM) 35X15QS (a cationic surface active agent available from Imperial Chemical Industries PLC containing C₁₃ C₁₅ alkylmethylpoly(hydroxyethyl) ammonium methosulphate) was investigated.

The surface active agent was dissolved in ethanol (a solubilising agent) to give a 1 % v/v solution, i.e. a solution containing 1 % by volume of the surface active agent and 99 % by volume of the ethanol. A certain volume of this solution, which was different for each example so as to vary the amount of the surface active agent in the cooling composition, was then charged to the spray device followed by about 40 g of the R-134a.

The results of the electrostatic spray tests (in kilovolts (kV)) are shown in Table 2 together with the volumes of surface active agent/ethanol solution used and the amounts of the surface active agent contained in the cooling compositions of Examples 6 to 10.

TABLE 2

Example Volume of solution (*) Amount of Electro¬ added to the 40 g of SAA (*) in static

R-134a (μl) cooling spray composition test (kV)

(ppm by weight)

6 100 20 0.016

7 50 10 0.075

8 25 5 0.058

9 10 2 -0.024

10 5 1 -0.190

Control 0 0 29.0

(*) In Table 2 above, the reference to solution means the solution of the surface active agent in the ethanol and SAA means surface active agent.

Example 11

In this example, the performance of a cooling composition comprising 1,1,1,2-tetrafluoroethane (R-I34a) and cetyltrimethyl ammonium bromide (a cationic surface active agent) was investigated.

0.3 g of the surface active agent was dissolved in 5 ml of ethanol (a solubilising agent) and 50 μl of this solution were then charged to the spray device followed by about 40 g of the R-134a. The concentration of the surface active agent in the cooling composition was about 100 ppm on a weight basis. The cooling composition was then subjected to an electrostatic spray test as before. The charge generated on the surface of the disc as a result of the spraying was monitored by the electrostatic voltmeter and peaked at -0.140 kV.

Example 12

In this example, the performance of a cooling composition comprising 1,1,1,2-tetrafluoroethane (R-134a) and Lankrostat (TM) QAT (a cationic surface active agent available from Akcros Chemicals containing a quaternised fatty amine ethoxylate and an alcohol ethoxylate) was investigated.

1 μl of the surface active agent and 100 g of the R-134a were charged to the spray device to give a cooling composition comprising about 10 ppm of the surface active agent on a weight basis.

The cooling composition was then subjected to an electrostatic spray test as before. The charge generated on the surface of the disc as a result of the spraying was monitored by the electrostatic voltmeter and peaked at -100 volts (V).

Example 13

In this example, the performance of a cooling composition comprising 1,1,1,2-tetrafluoroethane (R-134a) and Lankrostat (TM) NP6 (a nonionic surface active agent available from Harcros Chemicals UK Ltd containing a polyether) was investigated.

The cooling composition was then subjected to an electrostatic spray test as before. The charge generated on the surface of the disc as a result of the spraying was monitored by the electrostatic voltmeter and peaked at -0.6 kV. Example 14

In this example, the performance of a cooling composition comprising 1,1,1,2-tetrafluoroethane (R-134a) and Catafor (TM) PU (a cationic surface active agent available from Rhone Pouienc Chemicals containing 80 % quaternary ammonium ethosulphate and 20 % 1,4-butane diol) was investigated.

The cooling composition was then subjected to an electrostatic spray test as before. The charge generated on the surface of the disc^' as a result of the spraying was monitored by the electrostatic voltmeter and peaked at -0.6 kV.

Examples 15 to 20

In these examples, the performance of a series of cooling compositions comprising 1,1,1,2-tetrafluoroethane (R-134a) and varying amounts of Lankrostat (TM) QAT (a cationic surface active agent available from Akcros Chemicals containing a quaternised fatty amine ethoxylate and an alcohol ethoxylate) was investigated.

A certain volume of the surface active agent, which was different for each example so as to vary the amount of the surface active agent in the cooling composition, was charged to the spray device followed by about 100 g of the R-134a.

The various cooling compositions were then subjected to an electrostatic spray test as before.

A control experiment was also conducted using neat R-134a as the cooling fluid. The neat R-134a was charged to an identical spray device and the electrostatic spray test was carried out using the same technique. The results of the electrostatic spray tests are shown in Table 3 together with the amounts of the surface active agent contained in the various cooling compositions (in ppm by weight).

TABLE 3

Example Amount of Electrostatic

SAA (*) in spray test cooling composition

(ppm by wt. )

15 1000 57 V

16 100 160 V

17 30 58 V

18 10 150 V

19 3 350 V

20 1 _320 V

Control 0 -11 kV

(*) In Table 3 above, SAA means surface active agent.

Claims

Claims :

1. A composition comprising at least one fluorine containing compound having a boiling point below 0°C selected from the

(hydro)fluorocarbons and the (hydro)fluorocarbon ethers and at least one surface active agent.

2. A composition as claimed in claim 1 wherein the

(hydro)fluorocarbons and (hydro)fluorocarbon ethers from which the at least one fluorine containing compound is selected have a boiling point below -10°C.

3. A composition as claimed in claim 2 wherein the

(hydro)fluorocarbons and (hydro)fluorocarbon ethers from which the at least one fluorine containing compound is selected have a boiling point below -15°C.

4. A composition as claimed in claim 3 wherein the

(hydro)fluorocarbons and (hydro)fluorocarbon ethers from which the at least one fluorine containing compound is selected have a boiling point below -20^βC.

5. A composition as claimed in any one of claims 1 to 4 wherein the at least one fluorine containing compound is selected from the hydrofluorocarbons.

6. A composition as claimed in claim 5 which comprises at least one C. , hydrofluorocarbon.

7. A composition as claimed in claim 6 which comprises at least one C. , hydrofluoroalkane.

8. A composition as claimed in claim 7 which comprises at least one hydrofluoroethane.

9. A composition as claimed in claim 8 which comprises 1,1, 1,2-tetrafluoroethane.

10. A composition as claimed in any one of the preceding claims wherein the at least one surface active agent is a liquid.

11. A composition as claimed in any one of the preceding claims which comprises at least one nonionic surface active agent.

12. A composition as claimed in claim 11 wherein the at least one nonionic surface active agent comprises a polyether.

13. A composition as claimed in any one of claims 1 to 10 which comprises at least one cationic surface active agent.

14. A composition as claimed in claim 13 wherein the at least one cationic surface active agent comprises a quaternary ammonium salt.

15. A composition as claimed in claim 14 wherein the quaternary ammonium salt comprises one or more compounds having the formula:

wherein

R is a long chain aliphatic hydrocarbon group; each of X, Y and Z are independently H or an organic moiety; and

A is a counterion.

16. A composition as claimed in claim 15 wherein the quaternary ammonium salt comprises one or more compounds of Formula I in which R is a long chain alkyl group.

17. A composition as claimed in claim 16 wherein the quaternary ammonium salt comprises one or more compounds of Formula I in which R is a C₁₀_₂₀ alkyl group.

18. A composition as claimed in any one of claims 15 to 17 wherein the quaternary ammonium salt comprises one or more compounds of Formula I in which each of X, Y and Z are independently selected from the C, . alkyl groups and the alkoxylate groups.

19. A composition as claimed in claim 18 wherein the quaternary ammonium salt comprises one or more compounds of Formula I in which each of X, Y and Z are independently selected from methyl, ethoxylate groups, propoxylate groups and ethoxylate-propoxylate groups.

20. A composition as claimed in any one of claims 15 to 19 wherein the quaternary ammonium salt comprises one or more compounds of Formula I in which A is a methosulphate or ethosulphate ion.

21. A composition as claimed in any one of the preceding claims wherein the surface active agent constitutes from 0.1 to 10,000 ppm by weight of the total weight of the composition.

22. A composition as claimed in claim 21 wherein the surface active agent constitutes less than 100 ppm by weight of the total weight of the composition.

23. A process for cooling an article which comprises contacting that article with a cooling composition as claimed in any one of claims 1 to 22.

24. A spray device containing a cooling composition as claimed in any one of claims 1 to 22.

25. An aerosol containing a cooling composition as claimed in any one of claims 1 to 22.