Aqueous semi-synthetic metalworking fluid compositions containing alkyl alcohol amines

Abstract

The present invention describes an aqueous semi-synthetic metalworking fluid comprising a base oil, an organic acid, an emulsifier, an additive concentrate, water, and a microbial growth control agent comprising an alkyl alcohol amine.

Description

[Technical field]

[0001] Embodiments relate to methods of controlling microbial growth in metalworking fluids comprising adding alkyl alcohol amines. Other embodiments relate to semi-synthetic metalworking fluid compositions that include microbial growth control agents that include a specific class of alkyl alcohol amines.

[0002] Introduction Metal working fluids (MWFs) are used for lubrication during metal cutting and tool forming processes. These fluids help cool metalworking tools, remove cutting debris from the tool / workpiece interface, and provide acceptable post-machining finishes. Amines are common MWF components that are widely used in various applications due to their anti-corrosion, neutralizing, and pH adjusting properties. Organic amines are typically used as corrosion inhibitors because MWFs degrade over time due to microbial growth that negatively impacts fluid performance, and the microorganisms feed on the active ingredients in the fluid.

[0003] Such microbial growth in MWFs can cause serious problems in metalworking processes in many forms, including general souring of the MWF, changes in the viscosity of the MWF, shortening of the shelf life of the MWF, and corrosion of tools and materials. In addition, the functionality of equipment and processes such as delivery nozzles, storage tanks, pipelines, and recycling system equipment can also be affected by microbial growth in the MWF. This souring increases the cost of the MWF, accelerates the corrosion rate, and reduces the efficiency of metalworking. Thus, there is an unmet need in the MWF industry for components that do not support microbial growth and maintain performance over extended periods of time.

[0004] Existing MWFs are typically classified as neat oil, soluble oil, semi-synthetic fluids, or synthetic fluids, with each category exhibiting different functions of cooling, lubrication, rust prevention, and cleaning. Soluble oil MWFs contain 50-70 wt% neat oil, with the remainder of the MWF being antiwear / extreme pressure additives, and emulsifiers. Neat oil and soluble oil typically do not provide the same level of cooling compared to water-based metalworking fluids. Synthetic fluids typically cannot provide good lubrication performance because their lubrication function is affected by the back-dissolution of polyalkylene glycols when the temperature is higher than the cloud point. Semi-synthetic materials offer the possibility of simultaneously providing good lubrication and cooling properties for use in demanding applications. A typical semi-synthetic fluid consists of oil, organic acid, emulsifier, lubricant, amine, water, and other components. The amount of water in such semi-synthetic MWFs is typically up to 50-60% by weight, with about 10-40% by weight base oil, about 10-20% by weight emulsifier, about 10-20% by weight amine, and other functional additives such as acids, lubricants, solubilizers, biocides, etc. Semi-synthetic MWFs are usually diluted at the end user's site with additional water to a concentration of 1-20% by weight base oil, more typically 5-7% by weight, by weight of the diluted formulation.

[0005] In semi-synthetic fluids, emulsifiers are often added to form stable oil-in-water dispersions. Emulsifier particles are located around the oil droplets and impart a negative charge that binds them to water molecules. The size of such emulsified oil droplets is very important for fluid performance, since generally the smaller the size of the emulsion, the easier it is to penetrate the interface of the cutting zone. Emulsifiers also contribute to the stability of semi-synthetic fluids.

[0006] Semi-synthetic fluids degrade partially over time due to microbial growth that adversely affects fluid performance as the microorganisms feed on the active ingredients in the fluid. Such microbial growth in MWFs can cause serious problems in metalworking processes in many forms, including general souring of the MWF, viscosity changes of the MWF, shortening of the MWF shelf life, and corrosion of tools and materials. In addition, the functionality of equipment and processes such as delivery nozzles, storage tanks, pipelines, and recycling system equipment can also be affected by microbial growth in the MWF. This souring increases the cost of the MWF, accelerates the corrosion rate, and reduces the efficiency of metalworking. The most common solution to control microbial growth is to add biocides and amine alcohols to a given MWF, either continuously or as a batch process. However, biocides and some secondary amine alcohols are limited by regulatory restrictions, and most of the biocidal chemicals release formaldehyde over time, which is harmful to human health.

[0007] Therefore, it would be desirable to have new semi-synthetic metalworking formulations with new biocidal compositions that provide improved cooling, lubricity, concentrate stability, and extended shelf life without the environmental health and safety concerns of current fluids.

[0008] The present invention addresses at least some of the needs set forth above. Summary of the Invention

[0009] The present invention relates to a method for controlling microbial growth in a metalworking fluid, the method comprising the addition of at least one alkyl alcohol amine corresponding to a particular formula. The present invention also describes an aqueous semi-synthetic metalworking fluid comprising a base oil, an organic acid, an emulsifier, an additive concentrate, water, and a microbial growth control agent comprising an alkyl alcohol amine falling within the scope of a particular formula. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Depending on their composition, metalworking fluids are classified as neat oil, soluble oil, semi-synthetic fluids, or synthetic fluids. Soluble oil MWFs contain 50-70% oil by weight, the remainder being anti-wear / extreme pressure additives and emulsifiers. Semi-synthetic MWFs contain significant amounts of water, typically up to 50-60% by weight. Semi-synthetic fluids have balanced lubrication and cooling performance, making them attractive for use as MWFs.

[0011] The present invention relates to semi-synthetic metalworking fluids, which comprise water, one or more base oils, one or more organic acids, one or more emulsifiers, one or more lubricants, one or more amines, which function as pH adjusters and / or microbial growth control agents, and at least one amine comprises at least an alkylamine alcohol of formula (I):

[0012] [ka] wherein R1 is H or a C1 or C2 alkyl group and R2 is a C3-C6 alkyl or a C5 or C6 cycloalkyl group. In many embodiments, R1 is preferably H. In many embodiments, R2 is preferably a straight chain alkyl group having 3 to 5 carbon atoms.

[0013] Such alkylamine alcohol materials can be obtained commercially or can be produced by the alkoxylation reaction of alkylamines with oxides (such as ethylene oxide, propylene oxide, butylene oxide, etc.) as is commonly known in the art.

[0014] The microbial growth control agent may further include one or more additional antimicrobial materials, such as glycol ether amines, which may be used in combination with the materials disclosed above to achieve a particular microbial growth control goal. The concentration of the microbial growth control agent / pH adjuster in the MWF (including the alkylamine alcohol of formula (I)) may range from 1, 4, 6, 8, or 10 percent by weight of the formulation to 30, 25, 15, or 12 percent by weight of the formulation. Preferably, the alkylamine alcohol of formula (I) comprises 2, preferably 3, or even 5 percent by weight of the MWF to 25, preferably 20, or even 15 percent by weight.

[0015] The semi-synthetic MWF of the present invention also includes a base oil. The base oil may be any base oil generally known in the art for use in MWFs. Preferably, the base oil is a base oil selected from tall oil, naphthenic oil, paraffinic oil, or ester oil, or combinations thereof. The concentration of the base oil in the MWF may range from 5, 7, 10, or 15 weight percent of the formulation to 50, 45, 40, or 35 percent of the formulation.

[0016] The water used in the present formulations is preferably deionized water and may comprise at least 20, preferably 25, 30, or even 35 weight percent of the formulation, up to 70, 65, 60, 55, or even 50 weight percent of the formulation. It is contemplated that these formulations may be further diluted with additional water prior to use, modifying these ranges accordingly. For example, prior to use, the formulations may be diluted such that the base oil concentration is 1 to 20 weight percent, more typically 5 to 7 weight percent of the diluted formulation.

[0017] The semi-synthetic MWF of the present invention also includes one or more organic acids as solubilizers and / or corrosion inhibitors. Preferred organic acids include 2-ethylhexanoic acid, azelaic acid, tall oil fatty acid, 12-hydroxyl-(cis)-9-octadecenoic acid, dicarboxylic acid, and 9-octadecenoic acid. The concentration of the organic acid in the MWF can range from 2, 3, 4, or 5 weight percent of the formulation to 12, 10, 8, or 7 percent of the formulation.

[0018] The semi-synthetic MWF of the present invention also includes one or more emulsifiers. The emulsifiers can be anionic, cationic, or nonionic. Examples of suitable anionic surfactants or emulsifiers are alkali metal, ammonium, and amine soaps. The fatty acid portion of such soaps preferably contains at least 10 carbon atoms. The soaps can also be formed "in situ", in other words, the fatty acid can be added to the oil phase and the alkaline material can be added to the water phase.

[0019] Other examples of suitable anionic surfactants or emulsifiers are alkali metal salts of alkyl-aryl sulfonic acids, sodium dialkyl sulfosuccinate, sulfated or sulfonated oils such as sulfated castor oil; sulfonated tallow, and alkali salts of short chain petroleum sulfonic acids.

[0020] Suitable cationic surfactants or emulsifiers are salts of long chain primary, secondary, or tertiary amines, such as oleylamide acetate, acetylamine acetate, didodecylamine lactate, acetate of aminoethyl-aminoethylstearamide, dilauroyltriethylenetetramine diacetate, 1-aminoethyl-2-heptadecenylimidazoline acetate; and quaternary salts, such as cetylpyridinium bromide, hexadecylethylmorpholinium chloride, and diethyldidodecylammonium chloride.

[0021] Examples of suitable nonionic surfactants or emulsifiers are condensation products of higher fatty alcohols with ethylene oxide, such as the reaction product of oleyl alcohol with 10 ethylene oxide units; condensation products of alkylphenols with ethylene oxide, such as the reaction product of isooctylphenol with 12 ethylene oxide units; condensation products of higher fatty acid amides with 5 or more ethylene oxide units; polyethylene glycol esters of long chain fatty acids, such as tetraethylene glycol monopalmitate, hexaethylene glycol monolaurate, nonaethylene glycol monostearate, nonaethylene glycol dioleate, tridecaethylene glycol monoarachidate, tricosaethylene glycol monobehenate, and tricosaethylene glycol dibehenate; polyhydric alcohol moieties, such as sorbitan tristearate, and higher fatty acid esters. ethylene oxide condensation products of polyhydric alcohol partial higher fatty acid esters and their intramolecular anhydrides (called mannitol anhydride, mannitan, sorbitol anhydride, sorbitan), such as glycerol monopalmitate reacted with 10 molecules of ethylene oxide, pentaerythritol monooleate reacted with 12 molecules of ethylene oxide, sorbitan monostearate reacted with 10 to 15 molecules of ethylene oxide, mannitan monopalmitate reacted with 10 to 15 molecules of ethylene oxide, etc.; long-chain polyglycols in which one hydroxyl group is esterified with a higher fatty acid and the other hydroxyl group is etherified with a low molecular weight alcohol, such as methoxypolyethylene glycol 550 monostearate (550 means the average molecular weight of the polyglycol ether). Combinations of two or more of these surfactants may be used, for example, cationic surfactants may be blended with nonionic surfactants, or anionic surfactants may be blended with nonionic surfactants.

[0022] Particularly suitable emulsifiers include ethoxylated or propoxylated C16-18 alcohols; ethoxylated C12-C15 alcohols; sodium alkanesulfonates and alkyl ether carboxylates.

[0023] The concentration of the emulsifier in the MWF can range from 4, 5, 6, 8, or 10 weight percent of the formulation to 25, 20, 15, or 12 percent of the formulation.

[0024] The semi-synthetic MWF of the present invention may also include one or more concentrated additives. When present, preferred concentrated additives include diethylene glycol butyl ether, ethylene glycol monobutyl ether, and propylene glycol butyl ether. When present, the concentration of concentrated additives in the MWF may range from 0.3, 0.5, 1.0, or 1.5 weight percent of the formulation to 2.5, 2.0, or 1.8 percent of the formulation.

[0025] The semi-synthetic MWFs of the present invention may also include other additives to provide additional functionality as generally known in the art.

[0026] The microbial growth controlled by the biocides of the present disclosure typically consists of contaminants that are a mixture of bacteria and fungi. Some exemplary fungal and bacterial5 inclusions include, but are not limited to, Aeromonas hydrophila (ATCC 13444), Candida albicans (ATCC 752), Desulfovibrio desulfuricans (ATCC 7757), Escherichia coli (ATCC 8739), Flavobacterium ferrugineum (ATCC 13524), Fusarium oxysporum (ATCC 7601), Klebsiella pneumoniae (ATCC 13883), Proteus mirabilis (ATCC 4675), Pseudomonas aeruginosa (ATCC 8689), Pseudomonas oleovorans (ATCC 8062), and Saccharomyces cerevisiae10 (ATTC 2338). The strains listed above may vary worldwide and the present invention is fully envisioned as a broad spectrum microbial growth control agent and / or biocide that can be used against any common MWF microbial contaminant. EXAMPLES

[0027] Experiments to test the effectiveness of formulations containing the microbial growth control agents of the present disclosure can be performed as follows: Table 1 contains a description of the materials used in these examples.

[0028] [Table 1]

[0029] A series of formulations are prepared according to Table 2 using different amines as listed in Table 3.

[0030] [Table 2]

[0031] [Table 3]

[0032] The examples and comparative examples were prepared by diluting the concentrated formulations 20 times with water.

[0033] Concentrated formulations are prepared as follows: Pour the indicated amount of deionized water into a container. Add mineral oil, EcoSurf SA-7, Dowfax 20A42, secondary alkane sulfonate, tall oil acid, and diacid (sebacic acid) to the water. Stir the formulation with a magnetic stirrer at 200 rpm at 60° C. for 1 hour. Add the indicated amine as a pH adjuster.

[0034] The concentrated formulation is then diluted 20 times based on the total volume of the concentrated formulation with process water or tap water (as shown in Table 3). The pH value is tested with a pH titrator (Mettler Toledo: #SevenMulti). If the pH value of the diluted formulation is below 9.5, additional monoethanolamine (1-2 drops) is introduced to increase the pH value to at least 9.5.

[0035] pH aging test: The pH values ​​of the prepared diluted formulations are tested at 0 days and 14 days by a pH titrator (Mettler Toledo: #SevenMulti). The samples are placed at room temperature.

[0036] [Table 4]

[0037] The pH loss rate after 2 weeks of aging should be as small as possible. IE1 with N-butylethanolamine shows the best results with only a 0.1% drop. CE2 and 3 with AMP-95 and dicyclohexylamine show that the pH loss is higher than IE1 but still controlled within 5%. CE1 with monoisopropanolamine is not as good in that the pH loss exceeds 10%.

[0038] Aluminum corrosion test: wash Al strip (#ADC12) with alcohol, weigh the strip. Immerse Al strip in test solution at 40°C for 48 hours using capped vial (half the volume of Al strip is in solution, half the volume of Al strip is exposed to air). Observe the corrosion of Al strip surface, measure the weight loss of Al strip, and use ICP-OES: Inductively Coupled Plasma Optical Emission Spectrometer (Perkin Elmer: #Optima 5300DV) to detect Al content in the formulation.

[0039] [Table 5]

[0040] The ICP-OES data show agreement with the qualitative observations of aluminum strip corrosion. Larger areas with yellow color indicate more corrosion and correspond to higher aluminum content in the test fluid. A qualitative description of "pass", "marginal", or "fail" is added to explain the observed results. CE4 with isomonopropanolamine and CE5 with AMP-95 are good in corrosion resistance, with less than 1 ppm aluminum leaching from the strip. Next to IE2 with N-butylethanolamine, CE6 was worse than any other sample, with more than 2 ppm aluminum content leaching into the fluid.

[0041] Antimicrobial test: The samples are run under the ASTM E 2275 method, which can be summarized as follows: The inoculum is a mixture of ATCC strains of bacteria and fungi as listed in Table 6. The emulsion product mixture inoculum is prepared by adding 0.1 mL of each bacterial overnight broth culture and 1.0 mL of each yeast broth culture to 10 mL of mold suspension and blending.

[0042] Administer 0.5 ml of the mixed inoculum to 50 grams of sample. This inoculum challenges the emulsion sample with high levels (106-107 colony forming units per gram of sample, CFU / g) of microorganisms. The challenged samples are mixed and stored in an incubator at 30°C for 7 days. This process is repeated for an additional five tests, adding the following amounts of inoculum to each sample: 0.5 ml for the second, 1.0 ml for the third, 1.0 ml for the fourth, and 3.0 ml for the fifth.

[0043] The inoculated emulsion samples are monitored for microbial growth by agar plate plating using standard streak plate techniques. Samples are plated 1 and 7 days after each microbial challenge. Samples are blended by shaking, vortexing, or stirring with a sterile stick or rod. Samples are streaked evenly onto TSA and PDA plates, preferably using a standard 10 uL inoculating loop. Streaked agar plates are incubated at 30°C (TSA) and 25°C (PDA) for 7 days.

[0044] All agar plates are checked 7 days after plating to determine the number of surviving microorganisms in the test sample. For plates streaked 7 days after inoculation, no colony growth is considered a pass.

[0045] [Table 6]

[0046] [Table 7] Pass = no colony growth Limit = Limit colony growth Fail = Significant colony growth

[0047] CE4 with isomonopropanolamine fails all the times of the test. CE5 with AMP-95 can pass the test until the end of the week, but fails the first time it comes into contact with microorganisms on the first day of every test. IE2 with N-butylethanolamine and CE6 with dicyclohexylamine show good antimicrobial performance, passing all the times of the test, whether it is the first or the seventh day.

[0048] A good amine pH adjuster must pass all three test criteria, so N-butylethanolamine performs well overall.

Claims

1. 1. A semi-synthetic metalworking fluid comprising: a. at least one base oil; b. at least one microbial growth control agent comprising an alkylamine alcohol having the structure: 【Chemistry 1】 In the formula, R １ is H or a methyl or ethyl group, R ２ is a C3-C6 alkyl group or a C5-C6 cycloalkyl group; and c. one or more organic acids; d. one or more emulsifiers; e. one or more additive concentrates; f. Water.

2. R of the microbial growth control agent １ is H.

3. 2. The semi-synthetic metalworking fluid of claim 1, wherein R2 is a C3 to C6 alkyl group or a C5 to C6 cycloalkyl group.

4. The semi-synthetic metalworking fluid of claim 1 , wherein the microbial growth control agent further comprises another amine.

5. The semi-synthetic metalworking fluid of claim 1 , wherein the microbial growth control agent is n-butylethanolamine.

6. 2. The semi-synthetic metalworking fluid of claim 1, wherein the microbial growth control agent is n-cyclohexylethanolamine.

7. 10. The semi-synthetic metalworking fluid of claim 1, wherein the base oil is selected from naphthenic oils, paraffinic oils, ester oils, and mixtures thereof.

8. 2. The semi-synthetic metalworking fluid of claim 1, wherein the emulsifier is selected from ethoxylated or propoxylated C16-18 alcohols, ethoxylated C12-C15 alcohols, sodium alkanesulfonates, and alkyl ether carboxylates, and mixtures thereof.

9. 2. The semi-synthetic metalworking fluid of claim 1, wherein the solubilizer / corrosion inhibitor is selected from ethylhexanoic acid, azelaic acid, tall oil fatty acid, 12-hydroxyl-(cis)-9-octadecenoic acid, dicarboxylic acid, 9-octadecenoic acid, sebacic acid, and mixtures thereof.

10. 10. The semi-synthetic metalworking fluid of claim 1, wherein the additive concentrate is selected from diethylene glycol butyl ether, ethylene glycol monobutyl ether, propylene glycol butyl ether, and mixtures thereof.

11. The semi-synthetic metalworking fluid of claim 1 , wherein the microbial growth control agent is present in an amount of 6 to 15 weight percent of the semi-synthetic metalworking fluid.

12. The semi-synthetic metalworking fluid of claim 1 , wherein the base oil is present in an amount of 10 to 45 weight percent of the semi-synthetic metalworking fluid.

13. The semi-synthetic metalworking fluid of claim 1 , wherein the emulsifier is present in an amount of 5 to 20 weight percent of the semi-synthetic metalworking fluid.

14. The semi-synthetic metalworking fluid of claim 1 , wherein the solubilizer is present in an amount of 3 to 10 weight percent of the semi-synthetic metalworking fluid.

15. The semi-synthetic metalworking fluid of claim 1 , wherein the water is present in an amount of 20 to 60 weight percent of the semi-synthetic metalworking fluid.

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