US 2084950 A
Description (OCR text may contain errors)
Patented June 22, 1937 PATENT' OFFICE COMPRESSION g FLUORINATED HYDRO- ARBON S Frederick Baxter Downing, Carneys Point, and Anthony Francis Benning, Pennsgrove, N. 3., assignorsto E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware v I No Drawing.
cation during such compression.
Gaseous fiuorinated aliphatic hydrocarbons,
particularly the fluorochloro hydrocarbons, have recently found rather wide use as refrigerants. Thesecompounds, while advantageous in many respects, have a definite disadvantage overthe 1o strongly polar refrigerants such as sulfur dioxide and ammonia in that they are generally miscible in all proportions with hydrocarbon lubricating oils. This property is disadvantageous because in a refrigeration system where the reserve supply of lubricant is in contact with the refrigerant vapor, the oil will dissolve the refrigerant resulting, particularly during shutdowns, in all of the refrigerant collecting in the oil reserve chamber. When now the machine is started up, violent ebullition of'the refrigerant from the oil carries the lubricant with it into other parts of the system, leaving the compressor without sufilcient oil to operate properly. This, of course, causes undue wear. Hence, under such conditions of operation, some means must be provided for the return of the lubricant to the compressor. In the case of sulfur dioxide and ammonia, the oil dissolves but a small quantity of refrigerant and the difficulty described above is not encountered.
It is an object of the present invention to provide a method of compressing gaseous fluorinated aliphatic hydrocarbons under new and improved lubricating conditions. A further ob- Ject is to provide a method of compressing gaseous fluorinated aliphatic hydrocarbon refrigerants in the ordinary type of refrigeration system wherein the reserve supply of lubricant is in contact with the refrigerant vapor, characterized by the use of a lubricating fluid which has good lubricating properties and which does not tend to dissolve excessive amounts of the fiuorinated aliphatic hydrocarbon. More specific objects are to accomplish the foregoing objects with fluorochloro aliphatic hydrocarbons, and more particularly difiuorodichloromethane. Other objects will appear hereinafter. I
These objects are accomplished by employing liquid organic esters of' phosphorus acids as lubricants. in systems for the compression of fluorinated aliphatic hydrocarbons.
Application March as, 1935, Serial No. 13,174
I Eramplel Difluorodichloromethane was compressed in the type of compressor ordinarily employed in household refrigerators using technical tricresyl phosphate as a lubricant. The proportions of technical tricresyl phosphate corresponded with the volume'proportions of oil normally employed in the usual sulfur dioxide household refrigerator compressor. Excellent results were obtained. The difiuorodichloromethane was not miscible with the technical tricresyl phosphate as in the case of oil, and although a study ofthe solubility properties 'of tricresyl phosphate, as given below, indicates that some of the fluorochloro hydrocarbon will be dissolved by the organic phosphate ester, nevertheless this solvent action did not interfere with the operation of the compressor and highly satisfactory results were obtained both before and after shut-downs. No undue wear on the compressor parts was evident.
Good results were also obtained in the compression of difiuorodichloromethane in a largesize compressor.
Technical tricresyl phosphate is a mixture of the esters and mixed esters of the isomeric cresols. Methods of obtaining it are known in the art. One method, for example, is to react a technical mixture of the isomeric cresols with phosphorous oxychloride.
Some of the properties of this material which affect its use for the purpose described above are given below:
Properties of technical tricresyl phosphate periinent to its use as a lubricant for fluorz'nated hydrocarbons Saybalt viscosity at F. seconds Saybolt viscosity at 210 F do 39. 6 Viscosity index. -50
. Pour point degrees F -20 Pour point saturated with CF2C12 d0 -20 Flash point (open cup) do 475 Fire point do 620 Almen film strength lbs. per sq. in 30, 000 Solubility in CFzClz (77 F.) per cent 12 Solubility CFzClz in tricresyl phosphate (77 F.) per cent 45 Of the properties given above, the high Almen film strength and non-miscibility with fluorochloro hydrocarbons may be noted as being especially desirable.
Example II Instead of difluorodichloromethane, mono- Example I with correspondingly good results.
Example III Tetrafluorodichloroethane may be compressed as in Example I with good results.
Similarly, the invention may be applied to the treatment of other gaseous fluorinated aliphatic hydrocarbons, as described, for example, in, Midgley, Henne and McNary, Reissue Patent 'No- 19,265, dated August 7, 1934.
Instead of technical tricresyl phosphate, other 1 liquid organic esters of phosphorus may be employed as, for example, any of the following: tri- (ortho-cresyl) phosphate; tri (meta cresyl) phosphate; tri-(para-cresyl) phosphate; phenyldi-(ortho-, meta-, or para-cresyl) phosphates;
' mixed isomeric di-cresyl-phenyl phosphates; di-
phate, dimyristyl phosphate, dibutyl phosphate and dicyclohexyl phosphate. Similarliquid organic esters of phosphorus, thiophosphoric,. meta-phosphoric and pyrophosphoric acids and mixtures containingthem may be used. In general, we prefer-to employ the neutral and acidic esters of the phosphorus acids;
The term lorol is used to describe a mixture ofv esters or mixed esters derived from a mixture of alcohols containing mostly lauryl alcohol but also containing some decyl and myristyl alcohols. The term ocenol is applied to a mixture-of primary aliphatic alcohols having 12 to 18 carbon atoms and consisting mainly of oleyl alcohol.
Such a mixture usually has an iodine value of,
A preferred class ofthe organic phosphorus esters may be represented by the following general formula:
where X, Y and Z represent H or lower aliphatic hydrocarbon radicals such as methyl, ethyl, isopropyl and butyl but maynot all be --H at the same time, and m, n, and o are 1, 2 or 3. u
Another preferred class oforganic phosphorus esters for our purpose are the normally liquid long chain aliphatic hydrocarbon monoand diesters of phosphorus acids preferably having at least one carbon chain of eight or more carbon atoms, e. g., dioctyl phosphate, monoand dilorol phosphates, monoand diocenol phosphates, and 4 octyl-lauryl phosphate.
A third preferred class of compounds are the normally liquid mixed aliphatic-aromatic difluorotrichloromethane may be compressed as in esters of phosphorus acids, as, for example, mixed tertiary amyl-phenyl phosphate and lorol-cresyl phosphate.
The liquid organic esters of phosphorus acids are preferably employed in undiluted state, that is, without the-addition of material amounts of solvents or diluents, particularly those diluents which are poorer'lubricants or tend to dissolve the fluorinated aliphatic hydrocarbon. dilution is to be made non-polar lubricants rather than polar lubricants are preferred. Thus, polar lubricants typified by polyhydric alcohols such as glycerin are not as good lubricants as the organic phosphorus esterstypified by tricresyl phosphate.
This invention has been instrumental in solving one of the more diflicult problems in the compression of fluorinated hydrocarbons, particularly in the field of household refrigeration. It has also been satisfactorily used in larger scale compression systems. i
As many apparently widely different embodiments of this invention-may be made without dc parting from the spirit andscopethereof, it is" to be understoodthat we do'not limit ourselves to the'specific embodiments thereof except as defined inthe appended claims. i
We claim: v 1
1. The method'of' compressing gaseous fluorinated aliphatic hydrocarbons which comprises compressing the gaseous fiuorinated hydrocarbons in the presence of lubricants consisting of liquid organic esters of phosphorus acids, said If any liquid organic esters being substantially immiscible with the fluorinated aliphatic hydrocarbons. 2. The method of compressing gaseous diflu-' orodichloromethane which comprises compressing the difiuorodichloromethane in the presence'of a lubricant consisting. of liquid organic esters of phosphorus acids having the following general formula I where X, Y and Z represent -H or lower aliphatic hydrocarbonradicals but may'not all be H at the same time, and m, n, and '0 are 1, 2-or 3.
3. The method of compressing gaseous difluorodichloromethane which comprises compressing the difluorodichloromethane in. the presence of a lubricant consisting of technical tricresyl .phosphate.
in: the gaseous fluorinated hydrocarbons in the presence of liquid organic esters selected from the class consisting of aromatic diand triesters of phosphorus acids, normally liquid long chain aliphatic hydrocarbon monoand di-esters of phosphorus acids, and normally liquid mixed aliphatic-aromatic esters of phosphorus acids.
7. In the process of refrigeration which comprises condensing a gaseous fluorinated hydrocarbon refrigerant and then evaporating the same, the step which comprises compressing said refrigerant in the presence of liquid organic esters of phosphorus acids which are substantially immiscible in said refrigerant.
8. In the process of refrigeration which comprises condensing a gaseous fluorinated hydrocarbon refrigerant and then evaporating the same in the vicinity of a body to be cooled, the step which comprises compressing said refrigerant in the presence of liquid organic esters selected from the class consisting of aromatic diand tri-esters of phosphorus acids, normally liquid long chain aliphatic hydrocarbon monoand di-esters of phosphorus acids, and normally liquid mixed aliphatic-aromatic esters of phosphorus acids.
9. In the process of refrigeration which comprises condensing a gaseous fluorinated hydrocarbon refrigerant and then evaporating the same, the step which comprises compressing said refrigerant in the presence of a lubricant conlisting of liquid organic esters of phosphorus acids having the following general formula where x, Y and Z represent --H or lower aliphat- 15 ie hydrocarbon radicals but may not all be -H at the same time. and m, n and o are 1', 2 or 3.
10. In the process of refrigeration which comprises condensing a gaseous fluorinated hydrocarbon refrigerant and then evaporating the 20 same, the step which comprises compressing said refrigerant in the presence of a lubricant consisting of technical tricresyl phosphate.
11'. The process of refrigeration which comprises compressing a gaseous fluorinated hydrocarbon refrigerant in the presence of a lubricant consisting of liquid organic esters of phosphorus acids which are substantially immiscible in said refrigerant, condensing said refrigerant, and then evaporating the same in the vicinity of a body to 30 be cooled.
FREDERICK BAXTER DOWNING. ANTHONY F. BENNING.