Emulsifier/detergent compounds for metalworking lubricants

Description

RELATED APPLICATIONS

This patent application is claiming the benefit of the U.S. Provisional Application No. 60/508760, filed Oct. 3, 2003, and entitled Emulsifier/Detergent Compounds for Metalworking Lubricants.

FIELD OF THE INVENTION

The subject invention relates generally to metalworking lubricant additives, and more specifically to improved emulsifier and detergent compositions prepared by co-sulfonating selected alkylbenzenes and oils with oleum.

BACKGROUND OF THE INVENTION

Metalworking continues to be a major industry throughout the world. During a metalworking operation, the metal in question may be forged, rolled, stamped, cut, formed or ground. Almost all metal objects from the smallest screws to large beams have been processed with at least one metalworking operation.

Successful metalworking requires the use of good fluids which can function both as a lubricant and a coolant. These lubricants and coolants are derived from a number of different types of metalworking fluids. Included are fatty acid soaps, formulated hydrocarbons, emulsified oils and aqueous solutions. These various products are used to manufacture products ranging from the drawing of wire to the topping of nut threads. For each manufacturing job, the metalworking fluid must be chosen to meet the demands of a specific application.

There are four major types of fluids used in today's metalworking industry. These products include:

Straight Oils

Soluble Oils

Chemical Solutions

Semichemical Solutions

This invention concerns the formation of emulsifiers or detergents which impart superior quality to soluble oils and straight oils used in the metalworking industry.

Soluble oils are actually oil-in-water emulsions that take advantage of the lubricity of oils and also the cooling properties of water, while at the same time provide corrosion protection. Soluble oils are the dominant type of water base metalworking fluid. The use of these materials instead of neat hydrocarbon based metal working fluids allows manufacturers to increase their production rate without sacrifices in surface finish, tool life, or die life. They also are cleaner than oil based formulations with reduced smoke or fumes at a much lower fire hazard. Soluble oils are also very versatile due to their composition. The required lubrication and cooling properties of soluble oil metalworking fluids can be adjusted simply by modifying the dilution ratio or changing the type or amount of lubricity additives.

Another advantage of soluble oils when compared to neat hydrocarbon based metalworking fluids is the cost. The formulated soluble oil concentrate normally costs more than a neat hydrocarbon formulated oil, however, the cost is significantly reduced because the concentrate can be diluted many times with significant volumes of water.

Because of these many benefits, approximately ninety percent (90%) of all metal removal operations use water based metalworking fluids. The subject invention provides a novel and superior emulsifying agent for such fluids.

Once again, it must be pointed out that the stability of the oil in water emulsion is the key to the success of the soluble oil formulation. The purpose of this invention is to prepare chemical agents that will provide this much needed emulsion stability.

Soluble oil metalworking fluids are well accepted by the metalworking industry and the presence of a hydrocarbon oil provides many operators and machinists with a significant degree of comfort and protection from unknown diluents. The soluble oil fluid is first made as a concentrate. The concentrate is then diluted with water by the industrial consumer in his own shop. The concentrate is supplied by a number of different companies throughout the world and a typical soluble oil concentrate is shown below:

TYPICAL SOLUBLE OIL

CONCENTRATE FORMULATION

	COMPONENT	% BY WEIGHT
	Mineral oil	70-85
	Emulsifier*	10-20
	Coupling agents	1-5
	Corrosion inhibitors	5-10
	EP additives	0-10
	Biocide	trace
	Water	0-5
	*The subject of this patent

The emulsifier described in this patent can also be used with synthetic oils or fluids to provide a hydrocarbon free formulation. For example, synthetic esters derived from pentaerythritol and C₁₂ to C₁₈ fatty acids can be used to replace the mineral oil shown in the above concentrate formulation. This synthetic formulation can then be used as a soluble oil in rolling compounds for steel.

It has been the goal for a number of years in the metalworking industry to replace chlorinated and active sulfur compounds in soluble oil formulations. Chlorine is classified as a hazard and is very difficult and costly to dispose of. Active sulfurized materials can promote the growth of bacteria in active metalworking fluids. The emulsifier described in this patent can be used to emulsify polymeric esters used in soluble oil formulations as lubricity agents. This enables the formulator to eliminate the chlorine and sulfur in many applications.

There are other performance advantages of the emulsifiers described herein. The sulfonate mixtures disclosed increase both lubricity and corrosion protection. Sulfonates are anionic surfactants which bear a negatively charged ion, which makes up the hydrophilic portion of the molecule. This property can be exploited to provide another advantage of the subject emulsifier. When the soluble oil-water mixture has come to the end of its useful life, the mixture can be treated with acid and alum or a polyelectrolyte to neutralize the charge and thereby eliminate the emulsifying property of the sulfonate. The oil portion of the metalworking fluid then separates out and can be readily removed. This factor is important for essentially eliminating disposal problems of soluble oil fluid.

The subject compositions can also be used successfully in metalworking formulations known as straight oils. These products are primarily derived from petroleum fractions containing metal working additives. Synthetic base stocks can also be used in the straight oil formulations. Straight oil metal working fluids contain no water and are sold ready to use. They are excellent lubricants but have limited cooling capacities.

Formulations containing the products of this invention are shown below:

TYPICAL STRAIGHT OIL

FORMULATION

	COMPONENT	Parts BY WEIGHT
	Diluent Oil	60-90
	Metal Sulfonates*	5-20
	EP additives	5-20
	Lubricity additives	0-10
	Antioxidents	0-4
	*The subject of this patent

It should be pointed out that the diluent oils can be paraffinic, naphthenic or synthetic and that the metal sulfonate can be derived from lithium, sodium, potassium or calcium, or mixtures thereof.

Straight oil metalworking lubricants continue to be the products of choice in many metalworking operations. They are important in applications requiring drawing and forming on low speed, high severity metal removal. The metal sulfonates compositions of the subject invention perform well in these applications. The major advantages of using these lubricants are low staining and clean burn off characteristics.

OBJECTS AND ADVANTAGES

The highlights, advantages and benefits of the subject invention are outlined as follows:

1. The sulfonate emulsifier and/or detergent composition contains a very wide range of molecular weights.

2. The molecular weights of the constituents of these sulfonate emulsifiers and/or detergent composition range from about 350 to over 650.

3. The composition contains a wide range of different molecular structures.

4. The composition of the emulsifier or detergent varies from a completely water-soluble sulfonate to a completely oil soluble sulfonate.

5. The composition exhibits superior emulsifying properties similar to the so-called natural sulfonates derived from lubricating oils.

6. The invention provides excellent stable emulsions.

7. The emulsifier or detergent of invention is compatible with natural oils, synthetic oils and white oils.

8. The color is consistently low and better than the natural sulfonate emulsifiers and better than most synthetic detergents.

9. The viscosity is consistently low and better than the natural sulfonate emulsifiers and most synthetic detergents.

10. The processing of the invention provides a more pure sulfonate emulsifier or detergent with a very low inorganic salt content.

11. The composition of the invention exhibits excellent rust prevention.

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.

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

The subject invention is prepared by oleum sulfonation of a mixture of lubricating oil and alkylbenzenes. These raw materials are selected from the following materials:

1. Solvent dewaxed heavy paraffinic oils with the following typical properties:

• • Specific gravity=0.88
  • Viscosity Index=95
  • IBP (approximately)=335° C.
  • Pour Point=−6° C.
  • Flash, COC=246° C.
  • Viscosity @ 40°=109-117 cSt
  • Suitable oils for this portion of the invention include Exxon Mobil's neutral petroleum lubricating oils designated as 600 Solvent Neutral and America's Core 600. It must be emphasized that the invention requires the use of two different lubricating oils. The other lubricating oil is lower in molecular weight and shown below.

2. Solvent dewaxed paraffinic oils which are lower in molecular weight and lighter oils than the materials shown above. These products have the following typical properties:

• • Specific gravity=0.88
  • Viscosity at 100° C.=11.4 cSt
  • Boiling point=330-600° C.
  • Viscosity Index=90=95
  • Flash, COC=238° C.

3. Linear mono alkylbenzenes containing alkyl side chains of 10-14 carbon atoms. These products are used for the preparation of biodegradable detergents. The molecular weight is especially suitable for the manufacture of liquid detergents. Some typical properties include:

• • Molecular weight=233-237
  • Density @ 15° C.=0.85-0.87
  • Bromine number=10 max.
  • Saybold color=29 min.
  • % Tetralins=0.5% max.
  • Initial Boiling Point=275° C.
  • Viscosity @ 20° C.=5-10 cps
  • Suitable products include Petrelab 500Q manufactured by Petresa Inc., and SASOL N-501 manufactured by Sasol Inc.

4. Heavy alkylbenzenes, primarily containing dialkylbenzene mixtures or derivatives of C₁₀-C₁₄ carbon alkylbenzene fractionation bottoms. These dialkylbenzenes are composed of unbranched groups. Typical properties include the following:

• • Molecular Weight=350-370
  • Density @ 15° C.=8.3-8.5
  • Viscosity @ 37.8° C.=12-30 cps
  • Specific Gravity=0.87
  • Flash Point Pensky Martens=181° C. min.
  • Suitable products include Vista 9050 manufactured by Sasol Co.

5. Linear Dialkylbenzenes, primarily containing dialkylbenzene mixtures derived from C₁₀-C₁₃ alkylbenzenes. The dialkylbenzenes in this alkylate are highly methyl group branched at the C-1 position. These materials are the fractionated bottoms. Typical properties include the following:

• • Molecular Weight=395-405
  • Initial boiling point=685° F.
  • Viscosity @ 40° C.=22.0 cSt
  • Specific gravity=0.89

The mixture of the above five components are essential and critical to the performance of this invention. The mixture of naturally derived sulfonates from the two different lubricating oils plus the special blend of different synthetic sulfonates result in an excellent emulsifier. It also must be emphasized that the difference in the structure between the two dialkylbenzenes is essential and an unexpected finding. In addition, the invention requires the use of two lubricating oils with different molecular weights.

There are allowable operating ranges for each of the components listed above which will allow the invention to perform satisfactorily as an emulsifier or detergent. These ranges are as follows:

	% SUITABLE RANGE
	BY WEIGHT

		Minimum	Maximum

	1. Heavy Paraffinic Oil	7	25
	2. Light Paraffinic Oil	7	25
	3. Linear Monoalkylbenzene	12	30
	4. Unbranched Dialkylbenzene	25	45
	5. C-1 Methyl Branched	7	18
	Dialkylbenzene

Not only is the above complex mixture required for this invention, but the conversion to the emulsifier or detergent requires specific conditions. As pointed out above, the complex mixture is converted to the sulfonate composition by first sulfonating the mixture with oleum and then converting the resulting sulfonic acid mixture to the metal sulfonate. It is important to the invention to sulfonate the mixture with oleum. This is in contrast to the current and most common industrial sulfonation procedure using gaseous sulfur trioxide. The majority of commercial oleum sulfonation has been replaced by the sulfur trioxide technique.

Thus the critical invention properties require:

1. A complex mixture of alkylbenzenes and lubricating oils;

2. Sulfonation by means of oleum only; and

3. Conversion to a metal sulfonate via specific processing steps.

The sulfonation procedure is outlined in the following steps:

Sulfonation

Outline of Method—Twenty percent (20%) oleum is reacted with the alkylate/oil mixture at a controlled rate and temperature. The reaction mass is then diluted with a paraffinic volatile solvent (selected from the group consisting of hexane, isohexane, heptane, isoheptane, octane, isooctane and others with an IBP of 250° F. or less), in this case heptane, and allowed to settle. The spent sulfuric acid settles to the bottom and can easily be removed from the heptane/product layer.

Procedure—A known and measured amount of alkylate/oil mixture selected from the ranges shown below, is charged to a suitable vessel:

	% SUITABLE RANGE
	BY WEIGHT

		Minimum	Maximum

	1. Heavy Paraffinic Oil	7	25
	2. Light Paraffinic Oil	7	25
	3. Linear Monoalkylbenzene	12	30
	4. Unbranched Dialkylbenzene	25	45
	5. C-1 Methyl Branched	7	18
	Dialkylbenzene

Suitable mixing of the alkylate is begun and 20 percent (20%) oleum (104.5% H₂ SO₄) is slowly added to the alkylate/oil mixture. Approximately 0.5 volumes of oleum is added based upon the total volume of alkylate/oil. The oleum addition rate should be controlled so that the temperature reaches, but does not exceed, 70° C. Then postmix the sulfonation mass for at least 15 minutes after the oleum addition has been completed.

Continue mixing and when the mixture reaches or is cooled to 45° C., approximately three volumes of heptane is added based upon the alkylate oil mixture. An example of the charge amounts for this procedure outlined above is as follows:

		Amount, gallons
	Alkylate/oil mixture	4,000
	20% Oleum	2,000
	Heptane	12,000
	Total	18,000

The above product is analyzed and then converted to a metal sulfonate emulsifier or detergent as follows:

EXAMPLE Sodium Sulfonate

Outline of Method—The heptane sulfonic acid from the above procedure is neutralized with sodium hydroxide. The neutralized reaction mass is settled and the brine layer is removed. The neutral sodium sulfonate solution is then heated and the heptane is removed via distillation. This procedure yields a product of this invention, a sodium sulfonate.

Procedure—A known, measured and analyzed amount of heptane sulfonic acid solution is charged to a suitable vessel. Mixing is begun and water and/or methanol is added to the sulfonic acid mixture. The amount of water required is approximately five percent (5%) based upon the weight of the heptane sulfonic acid charged. Mixing is continued for 15 minutes after the water addition and, then the acid is neutralized with sodium hydroxide/water solution. The concentration of the sodium hydroxide solution is not critical and concentrations up to 50 percent (50%) sodium hydroxide can be utilized. The amount of sodium hydroxide used is based upon the analysis and amount of the heptane sulfonic acid mixture. After mixing for 30 minutes, the mixture is re-analyzed after the sodium hydroxide solution has been added to make sure that the mixture is neutral. It is important to note that the temperature during water or sodium hydroxide solution addition must not exceed 130° F. The temperature must be controlled by the rates of addition. After the required neutralization, mixing is continued for at least 30 minutes. The mixing is then discontinued and the neutral sodium sulfonate mixture is allowed to settle for at least 12 hours. Following the required settling time, the brine layer has settled to the bottom of the tank, and the brine can be removed by decantation. The heptane organic layer is then transferred to a vessel suitable for solvent removal. Heating and mixing is begun, and the volatiles are removed via distillation. Oil can be added at this point in the process if the analysis reveals that an adjustment is required. Heating and mixing is continued to a bottoms temperature of 225° F. and, at this temperature, stripping with nitrogen gas is begun. When the product reaches 300° F., stripping is continued until the material reaches an acceptable flash point. The product will have the following typical properties:

	PROPERTY	% BY WEIGHT
	% Sodium Sulfonate	62-64%
	Flash, COC, ° F.	350-400
	Viscosity, SUS @ 100° F.	280-400
	% Water	0.1-2.0%
	ASTM Color	2-4
	Specific Gravity, 60° F.	0.97-0.99
	% Sediment	trace
	Molecular Weight	430-475

Examples of this invention have been selected and shown below and were derived from the following raw materials:

		Example 1	Example 2
P-500 Q	% Linear Monoalkybenzene	25	17
P-900 Q	% Unbranched dialkylbenzene	41	31
V-9050	% C-1 Methyl branched dialkylbenzene	14	12
600	% Heavy Paraffinic Oil	10	20
500	% Light Paraffinic Oil	10	20

These raw material mixtures of alkylates and oil were then sulfonated and converted to the corresponding sodium sulfonate using the procedures outlined above. The sodium sulfonates or final product mixture of sodium sulfonate and oil had the following analysis:

	Example 1	Test Method	Example 2

% Sodium Sulfonate	62.1	T1409A	62.0
Molecular Weight	445	AT1442	465
Flash, COC, ° F.	350	ASTM-D92	350
Viscosity, SUS @ 100° F.	64	ASTM-D445	47
% Water	<0.5	ASTM-D95	<0.5
ASTM Color (dilute)	<4.5	ASTM-D1500	3.0
Specific Gravity	0.966	T1406	0.975

These products of this invention were then tested for emulsion stabilization in hard and soft water. The products performed better than all existing commercial products in these tests. The stability in hard water was carried out in water containing 500 ppm calcium. Both example 1 and example 2 gave excellent, stable emulsions which exceeded the performance other commercially available sulfonate emulsifiers.

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. Thus, the scope of the invention should not be limited by the foregoing specifications, but rather only by the scope of the claims appended hereto.