Compositions – Vaporization – or expansion – refrigeration or heat or energy... – With lubricants – or warning – stabilizing or anti-corrosion...
Reexamination Certificate
1992-12-17
2001-04-17
Ogden, Necholus (Department: 1751)
Compositions
Vaporization, or expansion, refrigeration or heat or energy...
With lubricants, or warning, stabilizing or anti-corrosion...
C252S067000, C252S062200, C252S062200
Reexamination Certificate
active
06217791
ABSTRACT:
BACKGROUND OF THE INVENTION
i) Field of the Invention
The present invention relates to a lubricant for use in refrigerators and to a composition for use in refrigerators using said lubricant. More specifically, the present invention relates to a lubricant for use in refrigerators employing a chlorine-free Flon-type coolant such as Flon 134a (1,1,2,2,2-tetrafluoroethane), Flon 32 (difluoromethane), Flon 125 (1,1,2,2-pentafluoroethane), Flon 143a (1,1,1-trifluoroethane), Flon 152a (1,1-difluoroethane), Flon 134 (1,1,2,2-tetrafluoroethane), and the like, and a composition for use in refrigerators using said lubricant.
ii) Description of the Related Art
Flon-type coolants have conventionally been excellent for use as a coolant for refrigerators as they are chemically stable and have low toxicity. However, the recent Montreal Protocol decided that among these Flon-type coolants the use of chlorofluorocarbons such as Flon 12 (dichlorodifluoromethane) shall be totally abolished by the year 2000, because chlorofluorocarbons are a source of damage to the ozone layer in the stratosphere and contribute to global warming.
In such circumstances, Flon-type coolants not having chlorine in the molecules thereof, i.e. chlorine-free Flon-type coolants have been developed and are representatively illustrated by Flon 134a, described above, as an alternative to Flon 12.
However, because the polarity of chlorine-free Flon-type coolants without chlorine in molecules thereof such as Flon 134a and the like is higher than Flon 12, these chlorine-free Flon-type coolants have poor compatibility with naphthene mineral oils, alkylbenzene and the like which have been employed as lubricants for refrigerators and cause poor lubricity and frictional wear in the compressors of refrigerators. Therefore, a lubricant having good compatibility with Flon 134a and the like has been sought.
As a lubricant for refrigerators using Flon 134a as a coolant, polyoxyalkylene glycol has been disclosed in U.S. Pat. No. 4,755,316, Japanese Patent Laid-Open Nos. 01-271491, 02-129294, 03-103496 and the like, polyoxyalkylene glycol containing an acyl group as a modified compound of polyoxyalkylene glycol has been disclosed in Japanese Patent Laid-Open Nos. 01-198694, 03-33193, 03-79696, 03-81396 and the like, and polyoxyalkylene glycol containing halogen group has been disclosed in Japanese Patent Laid-Open Nos. 02-180987 and 02-132176.
However, since the above polyoxyalkylene glycols are highly hygroscopic and have poor stability, those modified compounds of polyoxyalkylene glycol have problems with corrosiveness and also, dialkylethers of polyoxyalkylene glycol have poor lubricity, so all of these lubricants have not been practical.
On the other hand, Japanese Patent Laid-Open Nos. 01-259093, 01-259095, 02-43290, 02-84491, 02-102296, 02-182780, 02-242888, 02-277097, 02-281098, 03-50297, 03-103496, 03-103497, 03-50297 and the like disclose monoalkylethers of polyoxyalkylene glycols that have good stability and no corrosive properties and are expected to be practicable.
However, the publicly known monoalkylethers of polyoxyalkylene glycol, described above, still have insufficient lubricity and further have poor compatibility with chlorine-free Flon-type coolants such as Flon 134a and the like.
Accordingly, it is an object of the present invention to provide a lubricant for use in refrigerators having superior compatibility with chlorine-free Flon-type coolants, good lubricity and resistance to hygroscopicity and also a composition for refrigerators using said lubricant.
SUMMARY OF THE INVENTION
The present inventors, as a result of having made various studies regarding lubricants for refrigerators employing chlorine-free Flon-type coolants, have achieved the present invention.
According to the present invention, there is provided a lubricant for use in refrigerators employing a chlorine-free Flon-type coolant whose molecules do not contain chlorine characterized in that said lubricant contains a monoethylether of polyoxyethyleneoxypropyleneglycol where the end group at the hydrogen terminal is an oxyethylene group, and which is represented by the following general formula (1):
CH
3
O(AO)
m
(CH
2
CH
2
O)
n
H
wherein the AO group represents an oxypropylene group, or a copolymeric group of oxypropylene groups and oxyethylene groups wherein the copolymeric form may be a block type and/or a random type, m is a number of 1≦m≦50, n is a number of 1≦n≦10, and the total content of the oxyethylene groups in the compound ranges from 5 to 60 percent by weight (based on total weight of formula (1) compound).
Further, according to the present invention, there is provided a composition for use in refrigerators characterized in that said composition contains a lubricant containing a monomethylether of polyoxyethyleneoxypropyleneglycol where the end group at the hydrogen terminal is an oxyethylene group, represented by the following general formula (1):
(4) CH
3
O(AO)
m
(CH
2
CH
2
O)
n
H
wherein the AO groups, and m and n each have their above defined meanings, and the content of oxyethylene groups in the compound remains as above defined, and a chlorine-free Flon-type coolant whose molecules do not contain chlorine, at a weight ratio of from 1:99 to 99:1.
In a compound represented by the general formula (1) described above used in the present invention, one end group should be a methyl group and the other end group should be a hydrogen group because, if hydrocarbyl groups rather than methyl groups are used as one end group, then the resulting lubricant has poor compatibility with Flon 134a, and if both end groups are methyl groups, then lubricity of the resulting lubricant may be deteriorated, and also if both end groups are hydrogen groups, then resistance to hygroscopicity of the resulting lubricants may be deteriorated, so these end groups can not be employed. Flon 134a is here used as being an illustrative and exemplary member of a preferred class of chlorine-free Flon-type coolants for present evaluation and descriptive purposes.
Also, the AO groups in the compound represented by the general formula (1) used in the present invention may be oxypropylene groups, or copolymeric groups of oxypropylene groups and oxyethylene groups wherein the copolymeric form may be block type and/or random type, and the polymerization degree, i.e. m, of said copolymeric group is a number in the range of 1≦m≦50 and preferably 5≦m≦45. If said polymerization degree, i.e. m, is over the above range, the resulting lubricants have poor compatibility with Flon 134 and the like.
In the compound represented by the general formula (1) used in the present invention, the end group of the hydrogen terminal should be oxyethylene groups and the polymerization degree, i.e. n, of said oxyethylene groups is a number in the range of 1≦n≦10, preferably 1≦n≦5 and more preferably 2≦n≦5. If the end group of the hydrogen terminal is an oxypropylene group, the lubricity way be deteriorated, and if the polymerization degree of the oxyethylene groups of the end group of the hydrogen terminal is greater than said upper limit, the pour point of the resulting lubricants may be increased.
Further, the total content of the oxyethylene groups in said compound of the general formula (1) should be from 5 to 60 percent by weight and preferably from 10 to 40 percent by weight. If the content of said oxyethylene group is less than said lower limit, the resulting lubricants can not obtain sufficient lubricity, and if the content has higher molecular weight, the resulting lubricants will have poor compatibility with Flon 134a and the like, and also if the content is greater than that range, the pour point of the resulting lubricants will increase.
A compound represented by the general formula (1) used in the present invention can be prepared by well-known processes. For example, said compound can be obtained by polymerizing methanol as a starting material with a mixture having an appropriate ratio of propyleneoxide and ethyleneoxide in the presence of
Baba Yuji
Kamakura Tamiji
Namiki Masato
Namiwa Kimiyoshi
Tanaka Noriyoshi
Asahi Denka Kogyo K.K.
Ogden Necholus
Olson & Hierl Ltd.
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