Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Organic -co- compound
Reexamination Certificate
2001-10-15
2003-09-09
McAvoy, Ellen M. (Department: 1764)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Organic -co- compound
C252S068000, C560S129000
Reexamination Certificate
active
06617289
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for producing an ester that includes a reaction in the presence of a Lewis acid catalyst and a phosphorus-containing reducing agent, and an ester, obtained by the production method. The present invention also relates to ester lubricating base stocks for grease, refrigerating machine oil and automotive engine oil and compositions containing the base stock.
2. Description of the Related Art
Esters are used in a wide range of fields such as cosmetics, pharmaceutical preparations, foods, electronic equipment, printing, and lubrication, etc. In recent years, with technological development in these fields using esters, each field requires esters with suitable qualities. For example, for esters used for grease, durability and anti-evaporation properties at high temperatures are required. For esters used for engine oil, long life and good thermal and oxidative stability are required. For esters used for refrigerating machine oils, high electric insulation properties and heat resistance are required, and it is also required that contaminants or conductive impurities are hardly contained, the acid value and hydroxyl value of the esters are low, and the hydrolytic stability and heat stability at high temperatures of the esters are excellent.
Esters can be obtained by a reaction between a carboxylic acid and an alcohol. In general, the reaction is carried out with an excessive amount of the carboxylic acid in order to obtain esters having a low hydroxyl value. In this esterification reaction, a Br&phgr;nsted acid such as sulfuric acid, hydrochloric acid, p-toluenesulfonic acid, methanesulfonic acid, or naphthalenesulfonic acid is commonly used as a catalyst. In the esterification reaction using such a Br&phgr;nsted acid, byproducts tend to be produced. The produced byproducts and the remaining catalyst are removed by purification by means of neutralization with an alkali, adsorption with an adsorbent, steaming, etc., which can be performed alone or in combination. However, it is difficult to sufficiently remove the byproducts and the remaining catalyst, and the remaining byproducts and catalyst are factors that may deteriorate the thermal and oxidative stability of the esters. Thus, there is no ester that satisfies the various requirements.
Japanese Laid-Open Patent Publication Nos. 54-91589 and 54-132502 describe a method for performing esterification in the presence of an acid catalyst such as a Brønsted acid and an ion exchange resin and phosphorous acid, hypophosphorous acid or salts thereof. Japanese Patent Publication No. 7-45437 describes a method for producing esters that includes a process of ester exchange in the presence of a mono-organic tin compound. Although these methods have some effects in that less colored esters can be obtained, the long-time thermal and oxidative stability is still insufficient.
In another example, less colored polyester is produced by adding a stabilizer containing a phosphorus-containing compound, a phenol-containing compound, a thioether-containing compound, an amine compound or the like, as disclosed in Japanese Laid-Open Patent Publication No. 7-309937. However, it is difficult to remove these stabilizers from the reaction product, and the stabilizer that remains in ester acts as an accelerator of deterioration of the ester so that sludge may be produced or discoloring may be caused when used at a high temperature for a long time.
Examples of Japanese Laid-Open Patent Publication No. 2000-508691 include a method using dibutyltin oxide as a catalyst for esterification. However, the ester obtained by this method is colored at high temperatures, and the ester has a high acid value, and, thus, the thermal and oxidative stability of the ester is insufficient. Furthermore, for all the engine oils described in PCT Publication No. WO 97/008277, esters produced in the absence of a catalyst are used as the base stock. The method described therein requires esterification reaction at a high temperature for a long time in the process of producing the esters, so that the esters are thermally deteriorated significantly during the reaction. Therefore, the heat resistance of the ester base stock is not sufficient, and there are problems with regard to the long-term stability.
Base catalysts are also known as catalysts for esterification. For example, N,N′-dicyclohexylcarbodiimide-4-(N,N-dimethylamino) pyridine, triphenyl phosphine-2,2′-dipyridyl sulfide or the like is used. However, when the base catalyst is used, the reaction mixture is colored blackish brown, and thus, high quality esters cannot be obtained.
As described above, there is no method for producing high quality esters that satisfies the requirements of various fields.
SUMMARY OF THE INVENTION
The method for producing an ester of the present invention includes reacting an alcohol with a carboxylic acid and comprises: reacting the alcohol with the carboxylic acid in a presence of a Lewis acid catalyst in an amount of 0.00001 to 0.005 mol and a phosphorus-containing reducing agent in an amount of 0.0003 to 0.005 mol with respect to one mol of carboxyl groups of the carboxylic acid, and separating a resultant ester.
In a preferred embodiment, the Lewis acid catalyst is at least one selected from the group consisting of titanium-containing Lewis acid catalysts, tin-containing Lewis acid catalysts, antimony-containing Lewis acid catalysts, germanium-containing Lewis acid catalysts, and zirconium-containing Lewis acid catalysts.
In a preferred embodiment, the alcohol is a neopentyl polyol having 2 to 6 hydroxyl groups, and the carboxylic acid is a monocarboxylic acid having 5 to 10 carbon atoms.
In a preferred embodiment, the alcohol is a neopentyl polyol having 2 to 4 hydroxyl groups, and the carboxylic acid is a monocarboxylic acid having 5 to 12 carbon atoms.
The ester of the present invention is obtained by a process comprising: reacting an alcohol with a carboxylic acid in a presence of a Lewis acid catalyst in an amount of 0.00001 to 0.005 mol and a phosphorus-containing reducing agent in an amount of 0.0003 to 0.005 mol with respect to one mol of carboxyl groups of the carboxylic acid, and separating a resultant ester, wherein the acid catalyst and the reducing agent are substantially removed from the resultant ester.
The ester lubricating base stock for grease of the present invention is obtained by a method comprising: reacting a neopentyl polyol having 2 to 6 hydroxyl groups with a monocarboxylic acid having 5 to 10 carbon atoms in the presence of a Lewis acid catalyst in an amount of 0.00001 to 0.005 mol and a phosphorus-containing reducing agent in an amount of 0.0003 to 0.005 mol with respect to one mol of carboxyl groups of the carboxylic acid, and separating a resultant ester, wherein the acid catalyst and the reducing agent are substantially removed from the resultant ester.
The ester lubricating base stock for refrigerating machine oil of the present invention is obtained by a process comprising: reacting a neopentyl polyol having 2 to 6 hydroxyl groups with a monocarboxylic acid having 5 to 10 carbon atoms in a presence of a Lewis acid catalyst in an amount of 0.00001 to 0.005 mol and a phosphorus-containing reducing agent in an amount of 0.0003 to 0.005 mol with respect to one mol of carboxyl groups of the carboxylic acid, and separating a resultant ester, wherein the acid catalyst and the reducing agent are substantially removed from the resultant ester.
The ester lubricating base stock for automotive engine oil obtained by a process comprising: reacting a neopentyl polyol having 2 to 4 hydroxyl groups with a monocarboxylic acid having 5 to 12 carbon atoms in a presence of a Lewis acid catalyst in an amount of 0.00001 to 0.005 mol and a phosphorus-containing reducing agent in an amount of 0.0003 to 0.005 mol with respect to one mol of carboxyl groups of the carboxylic acid, and separating a resultant ester, wherein the acid catalyst and the reducing agent are substantially removed
Hirao Keiji
Memita Michimasa
McAvoy Ellen M.
NOF Corporation
Webb Ziesenheim & Logsdon Orkin & Hanson, P.C.
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