Abstract:
Environmentally friendly, shelf-stable overbased calcium carboxylate compositions and their method of preparation are described. The subject compositions possess anti-oxidation and anti-wear properties superior to those associated with existing sulfonate compositions. The subject compositions are prepared by neutralizing a mixture of two different molecular weight aliphatic carboxylic acids or anhydrides in the presence of an aromatic or aliphatic hydrocarbon solvent; adding a mixture of calcium oxide and calcium hydroxide; adding methyl alcohol to promote the reaction; carbonating the mixture with carbon dioxide at temperatures between 80° F. and 120° F.; heating to 200°-250° F. and finishing carbonation; adding diluent oil to the crude product; clarifying the product in solvent; and removing the solvent.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/203,484, filed Dec. 22, 2008 and entitled, Highly Basic Calcium Carboxylate Compositions and Method Of Preparation. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The subject invention relates generally to motor oil and metal working compound additives, and more specifically to highly basic calcium carboxylate compositions having improved detergency, anti-oxidation and anti-wear properties. 
       BACKGROUND OF THE INVENTION 
       [0003]    Overbased additives can be found in practically every motor oil on the market. These materials, also known as “highly overbased” or simply “overbased” additives have provided motor oil with detergency, anti-wear, anti-corrosion and anti-rust properties as well as extreme pressure protection. The most widely used overbased compositions are the highly basic salts of alkyarylsulfonic acids (metal sulfonates). The reason for the use and popularity of the so-called highly basic metal sulfonates is the significant stability of these products when compared with the so-called highly basic metal carboxylates. 
         [0004]    The past three decades, however, have seen a significant change in the direction of the composition of both motor oils and metal working additive products. The main anti-wear, anti-oxidant additive that has been used in these industries is zinc dialkyldithiophosphate: 
         [0000]    
       
                 
         
             
             
         
       
     
         [0000]    As may be observed from the above molecular structure, zinc dialkyldithiophosphate compounds contain both sulfur and phosphorous, which can cause pollution, health problems and damage to catalytic converters. Because of these concerns, industry has emphasized the need to reduce both phosphorous and sulfur. However, there is also a concern that meeting this objective may necessitate a tradeoff of lower phosphorous and sulfur for much higher engine and machine wear. The automobile manufacturers are greatly concerned about this possibility and are therefore scrutinizing developments and environmental issues very closely. 
         [0005]    Highly basic calcium carboxylates, also known as “highly overbased” or simply “overbased” calcium carboxylates or soaps, are well known in the motor oil and metal working industries, but heretofore have not been known to possess the same degree of stability, anti-wear and anti-corrosion capabilities as the above mentioned products. The subject invention is directed toward overcoming these shortcomings. 
       SUMMARY OF THE INVENTION 
       [0006]    According to one aspect of the subject invention there is provided highly stable, highly basic calcium carboxylate compositions possessing superior anti-oxidation and anti-wear properties than existing sulfonate compositions. The subject compositions are prepared by neutralizing a mixture of two different molecular weight aliphatic carboxylic acids or anhydrides in the presence of an aromatic or aliphatic hydrocarbon solvent; adding a mixture of calcium oxide and calcium hydroxide; adding methyl alcohol to promote the reaction; carbonating the mixture with carbon dioxide at temperatures between 80° F. and 120° F.; heating to 200°-250° F. and finishing carbonation; adding diluent oil to the crude product; clarifying the product in solvent; and removing the solvent by distillation. 
         [0007]    Another aspect of the invention is that it can provide an environmentally friendly additive. This is because the product can be prepared from all natural ingredients. 
         [0008]    There are other properties of this invention that are important and significant. All of the motor oil formulations advantages for this new material can be summarized as follows: 
       Formulation Highlights 
       [0000]    
       
         
           
             Non-Sulfur Additive 
             Non-Phosphorous Additive 
             Anti-wear Properties 
             Contains Reserve Basicity 
             Provides Detergency 
             Phenol Free 
             Storage Stable 
             Additive Compatibility 
             Anti-oxidation Properties 
             Low Color 
             Low Odor 
             Low Viscosity 
             Non-toxic 
             Biodegradable 
             Excellent Solubility 
           
         
       
     
         [0024]    There has thus been outlined, rather broadly, the more important features of the invention in order that the detailed description thereof that follows may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional features of the invention that will be described hereinafter and which will form the subject matter of the claims appended hereto. In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting. As such, those skilled in the art will appreciate that the conception, upon which this disclosure is based, may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention. 
         [0025]    Further, the purpose of the foregoing abstract is to enable the U.S. Patent and Trademark Office and the public generally, and especially the scientists, engineers and practitioners in the art who are not familiar with patent or legal terms or phraseology, to determine quickly from a cursory inspection the nature and essence of the technical disclosure of the application. The abstract is neither intended to define the invention of the application, which is measured by the claims, nor is it intended to be limiting as to the scope of the invention in any way. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0026]    The subject invention is prepared from the following raw materials and processing agents:
       Calcium hydroxide   Calcium oxide   Aliphatic or aromatic solvent   A low molecular weight carboxylic acid   A high molecular weight carboxylic acid or anhydride   Methyl alcohol   Carbon dioxide
 
The importance and limits concerning these raw materials have been detailed below.
       
 
         [0034]    A hydrocarbon solvent to provide solubility for the carboxylic acids and process oil is used in the method of this invention. Suitable solvents can be selected from aliphatic or aromatic solvents with a boiling range from about 110° to about 350° F. These solvents can also provide the necessary low viscosity during processing. The minimum amount of solvent required is equal to the charge volume of the other raw materials. Increased solvent levels can be used and will aid processing in certain cases. Note that the solvent can be added anytime during the process prior to solvent removal. A typical and useful solvent is shown in the following table: 
       Mineral Spirits Aliphatic Solvent 
       [0035]      
         [0000]    
       
         
               
               
               
             
               
               
               
             
           
               
                   
                   
               
               
                   
                 Properties 
                 Typicals 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Flash Point PMCC 
                 105 
               
               
                   
                 API Gravity @ 60° F. 
                 52 
               
               
                   
                 Specific Gravity @ 60° F. 
                 0.7732 
               
               
                   
                 Lbs/Gallon 
                 6.437 
               
               
                   
                 Color, Saybolt 
                 +30 
               
               
                   
                 Kauri-Butanol Value 
                 32 
               
               
                   
                 Sulfur, H 2 S/Doctor 
                 Negative 
               
               
                   
                 Copper Strip Corrosion 
                 1 
               
               
                   
                   
               
             
          
         
       
     
         [0036]    At least two carboxylic acids chosen from one lower molecular weight acid and the second chosen from higher molecular weight acids or anhydrides. Suitable lower molecular weight acids include primarily fatty acids or mixtures of fatty acids, which have at least about 15 aliphatic carbon atoms and not more that about 25 aliphatic carbon atoms. Specific examples of suitable carboxylic acids include palmitic, stearic, oleic, linoleic, dodecanoic, and behenic. Also, suitable low molecular weight carboxylic acids include mixtures such as those found in the natural tall oil fatty acids. An example of these materials is the Arizona Chemical product SYLFAT® FA2 tall oil fatty acid. This material is typical of an acceptable carboxylic acid mixture and has the following important properties: 
       SYLFAT® FA2 
     Tall Oil Fatty Acid 
       [0037]      
         [0000]    
       
         
               
               
               
             
               
               
               
             
           
               
                   
                   
               
               
                   
                 Product Properties 
                 Typical Analysis 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Acid Value, mg KOH/gm 
                 196 
               
               
                   
                 Saponification Value 
                 197 
               
               
                   
                 % Fatty acids 
                 97.0 
               
               
                   
                 % Rosin Acids 
                 0.8 
               
               
                   
                 % Saturated acids 
                 2.0 
               
               
                   
                 % Oleic acid 
                 50 
               
               
                   
                 % Linoleic acid 
                 44 
               
               
                   
                 % Other Fatty acids 
                 4 
               
               
                   
                   
               
             
          
         
       
     
         [0038]    The higher molecular weight carboxylic acid is chosen from one or more acids or anhydrides having at least about 40 or more aliphatic carbon atoms. The preferred higher molecular weight compounds are the hydrocarbon-substituted succinic acids and anhydrides. These include, for example, polyisobutenyl succinic acid and polyisopropenyl succinic acids, polyisobentyl succinic acid and the anhydrides of these higher molecular weight carboxylic acids. A typical and acceptable polyisobutenyl succinic anhydride is OLOA 15500 manufactured by the Oronite Chemical Company. This material is derived from 1,000 molecular weight polybutene and is manufactured via the thermal process. It contains approximately 70 aliphatic carbon atoms. Its properties are as follows: 
       OLOA 15500 
     Polyisobutenyl Succinic Anhydride 
       [0039]      
         [0000]    
       
         
               
               
               
             
               
               
               
             
           
               
                   
                   
               
               
                   
                 Properties 
                 Value 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Specific Gravity @ 60° F. 
                 0.927 
               
               
                   
                 Density, lb/gal @ 60° F. 
                 7.72 
               
               
                   
                 Flash Point, COC ° C. 
                 200 
               
               
                   
                 Viscosity, cSt @ 100° C. 
                 140 
               
               
                   
                 Color, ASTM dilute 
                 3.0 
               
               
                   
                   
               
             
          
         
       
     
         [0040]    The carboxylic acids used in this invention can have more than one carboxylate group. Suitable acids include monocarboxylic acids, dicarboxylic acids and tricarboxylic acids. In specific cases, the corresponding amine or ammonium salts can be used as well as the amides and imides of these carboxylic acids. The lower molecular weight carboxylic acid provides the dispersancy to produce the highly overbased composition. The higher molecular weight carboxylic acid provides stabilization of the dispersed calcium carbonate colloid. The higher molecular weight also provides water tolerance and prevention of aglomeration of the basic portion of the invention. The total carboxylate amount including both carboxylates in the final product should be at least about 12 percent by weight. The optimum level for carboxylate is about 20 percent by weight in the final product. The ratio of higher molecular weight carboxylate to lower molecular weight carboxylate should range from about 1:15 up to 1:3. The optimum rate of high molecular weight is about 1:7. Please also note that the higher molecular weight carboxylic acid or anhydride can be added to the charge at any time before carbonation is begun. It can be added with the lower molecular weight carboxylic acid or added last immediately before carbonation. 
         [0041]    The basicity of the invention is provided by a mixture of calcium oxide and calcium hydroxide. A mixture is required because this provides stability during processing and high calcium utilization. The required operating mixture is from about 65 percent calcium oxide and 35 percent calcium hydroxide to about 70 percent calcium hydroxide to about 30 percent calcium oxide. At calcium hydroxide levels above about 70 percent, the stability of the overbased mass is affected and gellation can occur. At calcium oxide levels above about 65 percent, the carbonation efficiency decreases and the final product solubility in oil decreases. The specifications for both the calcium oxide and calcium hydroxide must also be closely controlled. Neither raw material can have water content or carbonate content above one percent. At levels above about one percent, the utilization of calcium decreases rapidly as well as the product quality. Large sediment level or very hazy product will result when the water and carbonate content exceed these levels. 
         [0042]    Diluent oil is needed in the final product to provide a fluid additive and to allow the invention to be totally soluble in lubricants. This oil can be chosen from a large number of suitable non-volatile diluent oils. The purpose of the oil is to adjust the final product for viscosity, basicity and carboxylate content. The oil soluble diluent oils may be a naphthenic oil or a paraffinic oil derived from petroleum. Examples of suitable diluent oils include the following materials: 
       Diluent Oil 
       [0043]      
         [0000]    
       
         
               
               
               
             
               
               
               
               
             
               
               
               
               
             
           
               
                   
                   
               
               
                   
                 Typicals 
                   
               
             
          
           
               
                   
                 Properties 
                 Naphthenic 
                 Paraffinic 
               
               
                   
                   
               
             
          
           
               
                   
                 Color, Neat 
                 0.5 
                 0.5 
               
               
                   
                 Viscosity @100° F., SSU 
                 105 
                 108 
               
               
                   
                 Flash Point, COC, ° F. 
                 340 
                 410 
               
               
                   
                 Pour Point, ° F. 
                 −45 
                 0 
               
               
                   
                 % Sulfur 
                 0.40 
                 0.40 
               
               
                   
                 API Gravity @ 60° F. 
                 25.5 
                 33.0 
               
               
                   
                   
               
             
          
         
       
     
         [0044]    Natural oils can be used if a food grade natural additive is desired. Suitable materials would include vegetable oils, corn oil, cottonseed oil, castor oil, lard oil, sperm oils, etc. The amount of oil employed is between about 25 percent and 75 percent by weight of the finished product. 
         [0045]    Alcoholic promoters are always used when forming these additives, and the literature discloses many types of monohydric and polyhydric alcohols. In addition, the patent art teaches the use of many combinations of many different alcohols. This invention is restricted to methyl alcohol. Other alcohols, combinations of alcohols, as well as substituted alcohols (e.g., alkoxy alcohols) do not work well in this invention and do not provide suitable final products. As a result, we use only methanol and restrict this invention to methyl alcohol. The amount of methanol is also crucial to the practice of this invention. The optimum and preferred range by weight is about one part methanol to about two parts calcium oxide/hydroxide and one part methanol to about four parts calcium oxide/hydroxide. Note that this invention requires a blend of calcium oxide and hydroxide. The water content of methanol is also important. At levels above about 0.5 percent water, the final product is hazy and unsuitable as a lubricant additive. 
         [0046]    Carbon dioxide is another essential raw material to practice this invention. It also has critical limits. The optimum level is about 0.78 to 0.88 moles of carbon dioxide per mole of excess calcium oxide/hydroxide. The excess calcium oxide/hydroxide is that amount used in excess of that required to neutralize the carboxylic acids used in the process. At mole ratios below about 0.78, the calcium oxide/hydroxide utilization drops significantly, the product clarification becomes very difficult and the process ceases to be economical. Above ratios of about 0.88, the products become hazy and are unsuitable as a lubricant additive. The temperature of carbonation is critical and the temperature must not exceed about 140° F. If the temperature is allowed to exceed about 140° F., the final product becomes hazy and is almost impossible to clarify. In addition, higher temperatures than about 160° F. can cause gel formation and a grease-like product. Thus, for use in a lubricant, the optimum temperature is about 120° F. Carbonation rate is also critical, and the required amount of carbon dioxide required should be added in a time period of about one to five hours. Under one hour, the efficiency of the reaction decreases causing high sediment and poor calcium oxide/calcium hydroxide utilization. Above about five hours, the product quality deteriorates, and a hazy product is the result. 
       General Process Description 
       [0047]    A suitable reactor is charged with a lower molecular weight carboxylic acid, a higher molecular weight carboxylic acid, aliphatic or aromatic solvent, and mixing of the charged materials is begun. The diluent oil can be added to the charge or later before final solvent removal. After a short mixing period, calcium oxide, calcium hydroxide and methanol are added. The temperature of the mass will increase because of the heat of reaction from acid neutralization. The mixture is then cooled and carbon dioxide is added at the bottom of the reactor. The temperature is controlled so that it does not exceed 120° F. during carbonation. The required carbon dioxide is added in about two hours. Heating is then begun to remove the volatile components. This includes solvent, methanol and water. The water is formed from the neutralization reaction between the carboxylic acids and the calcium compounds. At about 225° F., the crude product is stripped with more carbon dioxide. This step finishes the carbonation of any remaining calcium compounds and removes most of the water. Additional solvent is then added, the mixture is cooled and the material is clarified by filtration and/or centrifugation. The diluent oil can be added at this point in the process or earlier. The solvents are then removed by heating to about 300° F. and stripped with an inert gas. If desired, clarification can take place before or after solvent removal by filtration. The finished product will have the following properties depending upon the amounts of raw materials: 
       Highly Basic Calcium Carboxylate 
       [0048]      
         [0000]    
       
         
               
               
               
             
               
               
               
               
             
           
               
                   
                   
               
               
                   
                 Example 1 
                 Example 2 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 % Calcium carboxylate 
                 20 
                 20 
               
               
                   
                 Total base number 
                 200 
                 400 
               
               
                   
                 Viscosity, CST 100° C. 
                 9.4 
                 85 
               
               
                   
                 % Sediment 
                 0.015 
                 0.05 
               
               
                   
                 Color, ASTM dilute 
                 2.0 
                 3.0 
               
               
                   
                 % Calcium 
                 7.9 
                 15.2 
               
               
                   
                   
               
             
          
         
       
     
       Laboratory Example 
     Procedure 
       [0049]    A suitable laboratory reactor equipped with mixer, thermometer, condenser and addition funnels is charged with: 
         [0050]    200 gm. SYLFAT® FA2 Tall oil fatty acid 
         [0051]    560 gm. Mineral spirit solvent 
         [0052]    76 gm. Methanol 
         [0053]    20 gm. polyisobutenyl succinic anhydride 
         [0054]    Mixing is begun and 25 gm. of calcium oxide is added by means of a solid additional funnel. The heat of reaction raises the temperature of the mixture from ambient temperature to about 120° F. The mixture is cooled to about 80° F. and a mixture of 100 gm. of calcium hydroxide and 76 gm. of calcium oxide is added by the solid addition funnel to the well-mixed and stirred reactor. Carbonation of the material is then begun by means of a fritted glass tube below the surface of the liquid. Exactly 91 gm. of carbon dioxide is added over a 200-minute period at about 0.4 to 0.5 gm. per minute. Solvent removal is begun by heating the reactor. Also, immediately before solvent removal, 180 gm of 100 viscosity naphthenic oil is added to the reactor. Heating continued to about 225° F. and then stripping was begun with carbon dioxide. Heating and stripping was continued to about 300° F. The product was then filtered with admixed filter aid to remove any excess solids. The product was analyzed and additional oil was added to adjust the product to the desired specification. The final oil diluted material had the following properties: 
       Laboratory Example 
     Product Analysis 
       [0055]      
         [0000]    
       
         
               
               
               
             
               
               
               
             
           
               
                   
                   
               
               
                   
                 Product Properties 
                 Analysis 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Total Base Number 
                 408 
               
               
                   
                 Viscosity CST @ 100° C. 
                 85 
               
               
                   
                 Flash, ° C., PMCC 
                 165 
               
               
                   
                 % Calcium 
                 15.4 
               
               
                   
                 % Sediment 
                 0.02 
               
               
                   
                 % Calcium Oleate 
                 29 
               
               
                   
                   
               
             
          
         
       
     
       Commercial Example 
     Procedure 
       [0056]    A suitable reactor is charged with the following:
       1500 Gallons of SYLFAT® FA2 Tall oil fatty acids   6895 gallons of mineral spirits solvent   611 gallons of methanol       
 
         [0060]    Mixing and cooling is begun and 1220 lbs of calcium oxide is added to the reactor. Neutralization of the tall oil fatty acid then takes place. The temperature increases during the neutralization to about 110° F. Cooling during the neutralization prevents any excessive temperature rise. The temperature is adjusted to about 85° F. and the following raw materials are charged into the reactor in the order shown below:
       3660 lbs of calcium oxide   4780 lbs of calcium hydroxide   55 gallons of polyisobutenyl succinic anhydride       
 
         [0064]    The charge to the reactor is mixed for about 20 minutes and carbonation is begun. The carbon dioxide is charged in the bottom of the reactor through sparging tubes. A total of 4,630 lbs of carbon dioxide is added over about one hour and 57 minutes. The heat of reaction from the carbonation is easily controlled and the temperature rose to a maximum of 120° F. during the addition. After carbonation heating is begun, volatile materials are removed to a temperature of 225° F. The crude product is then stripped with carbon dioxide and approximately 575 lbs of carbon dioxide is used over about a ten-minute period. This step can be used to carbonate any remaining calcium hydroxide or oxide and to remove most of the water formed during the neutralization reaction. Heating is discontinued and an additional 3,000 gallons of mineral spirits is added to the reactor and cooling is begun. The product is then cooled to at least 140° F. At 95° F. the material is centrifuged to remove any unreacted solids. Following centrifugation, 3,000 gallons of 100 viscosity naphthenic oils is added and then the solvents and any residual water are removed by heating to 300° F. and stripping with nitrogen gas. The product had the following analysis: 
       Commercial Example 
     Product Analysis 
       [0065]      
         [0000]    
       
         
               
               
               
             
               
               
               
             
           
               
                   
                   
               
               
                   
                 Product Property 
                 Analysis 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Total base number 
                 205 
               
               
                   
                 % Calcium Carboxylate 
                 20.1 
               
               
                   
                 % Sediment 
                 0.04 
               
               
                   
                 Viscosity, CST 100° C. 
                 9.7 
               
               
                   
                 Color, ASTM dilute 
                 3.5 
               
               
                   
                 % Calcium 
                 7.7 
               
               
                   
                 Flash Point, PMCC, ° C. 
                 156 
               
               
                   
                   
               
             
          
         
       
     
         [0066]    This product was then tested for anti-oxidation and anti-wear properties. The following table compares a corresponding basic calcium sulfonate with the product of this invention, the basic calcium carboxylate: 
       Commercial Product 
     Performance Properties 
       [0067]      
         [0000]    
       
         
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                   
                   
               
               
                   
                 Blend Property 
                 A 
                 B 
                 C 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 % Base oil 
                 98 
                 98 
                 98 
               
               
                   
                 % Sulfonate 
                 1.0 
                 0.5 
                 0.0 
               
               
                   
                 Zinc dithiodiarylphosphate 
                 1.0 
                 1.0 
                 1.0 
               
               
                   
                 % Calcium Carboxylate 
                 0.0 
                 0.5 
                 1.0 
               
               
                   
                 RBOT (min) 
                 60 
                 147 
                 255 
               
               
                   
                 ASTM D 2670 (mm) 
                 0.0139 
                 Failure 
                 0.0069 
               
               
                   
                   
               
             
          
         
       
     
         [0068]    The tests indicate that the calcium carboxylate will provide better anti-wear and better anti-oxidation protection than the sulfonates that are now in general use throughout the industry. 
         [0069]    Although the present invention has been described with reference to the particular embodiments herein set forth, it is understood that the present disclosure has been made only by way of example and that numerous changes in details of construction may be resorted to without departing from the spirit and scope of the invention.