Synthetic metalworking fluid

Description

[0001] The present invention relates to metalworking fluids and more particularly a synthetic metalworking fluid which provides excellent lubrication and cooling for both hard and soft metals and is relatively bioresistant.

[0002] In most industrial metal working operations, a metalworking fluid is employed. Metalworking fluids act both as a coolant to maintain the temperature of the metal surfaces within a desired range and as a lubricant to lubricate the interface of the tool and metal. The cooling effect of the metalworking fluid adds considerable life to the cutting tools, such as drill bits, metal formers, etc., and also tends to prevent the warping or distortion of the metal. The lubricating properties, on the other hand, reduce the friction between the cutting tool and the metal, thereby reducing the power requirement of the machinery.

[0003] There are four types of metalworking fluids: straight oils, soluble oils, semi-synthetics and synthetics. Straight oils, which include mineral and vegetable oils, provide excellent lubricating properties but only minimal cooling. Soluble oils, i.e., emulsions of oil in water, provide both lubricity and cooling, and perform well on both hard metals, such as titanium and steel, and soft metals, such as aluminium. However, soluble oils are usually subject to rapid biodegradation and impaired lubricity after repeated use. Semi-synthetics, i.e., water solutions with smaller amounts of oil microemulsified, and synthetics, i.e., non-petroleum based emulsions or solutions provide improved lubricity and cooling, can be filtered, and can generally be used for much longer periods of time than soluble oils. However, neither synthetics nor semi-synthetics, free of chlorine, sulfur or phosphorous, have been successfully used on difficult machining operations, e.g., tapping of both hard and soft metals. Prior art synthetics have used chlorine, sulfur or phosphorous as extreme pressure additives in order to machine hard metals. These additives create a hazard to the environment, and chlorine can cause hydrogen embrittlement (stress cracking). Also, when cutting different metals it has been necessary to change metalworking fluids during the manufacturing process, increasing production time and causing disposal problems.

[0004] Soluble oils containing chlorine, sulfur or phosphorous extreme pressure additives have been used when a manufacturing process requires the working of two or more metals of significantly different hardnesses. However, soluble oils have several drawbacks. First, a single soluble oil may not be suitable for all metals in severe deformation processes such as tapping. Secondly, soluble oils have a typical useful life of 2-3 weeks, whereas synthetic fluids may be used for 12 months or more. Also, soluble oils present a disposal problem due to their petroleum base. If chlorine is present, an even greater disposal problem exists.

[0005] It would be desirable to provide a synthetic fluid, free of chlorine, sulfur and phosphorous, without the shortcomings of soluble oils, which may be used as a metalworking fluid when working two or more metals of different hardnesses. Preferably the fluid would provide good lubrication and cooling to both hard and soft metals, allowing a single fluid to be used for both types of metal even in severe applications.

[0006] The metalworking fluid of the present invention contains two major constituents, a polybutene selected from the group consisting of isobutylene-butene copolymers and polyisobutylenes, to provide the lubricity needed for working soft metals, and a polyether glycol, preferably having a carboxylate functionality, as an extreme pressure additive for working hard metals.

[0007] It has been found that this synergistic blend may be used to machine both hard and soft metals. The blend also unexpectedly provides lubricity superior to that obtained when polybutenes are used alone, and extreme pressure properties superior to those obtained when polyether glycols are used alone. One or more emulsifiers may be added to the polybutene and the polyether glycol when the concentrate is to be emulsified in water. Other common metalworking fluid constituents may also be added, if desired, but extreme pressure additives can be avoided.

[0008] The fluid is made in concentrate (neat) form, i.e., without the addition of water. The fluid may be used in its neat form or it may be diluted to a lesser concentration with water, if so desired, to form a microemulsion that can be water-dilutable. The amount of water can be 1 to 99% by volume of the total blend, including water.

[0009] The concentrate will preferably have a pH of from about 8 to about 10.5, more preferably from about 8.5 to about 9.5.

[0010] The isobutylene-butene copolymer used in one embodiment of the present invention is composed of about 95% to 100% by weight mono-olefins and about 0% to 5% by weight isoparaffins. Mono-olefins are a class of unsaturated aliphatic hydrocarbons with one double bond, obtained by cracking petroleum fractions at high temperatures. Isoparaffins are a class of aliphatic hydrocarbons characterised by a straight or branched carbon chain, and have the generic formula C_nH_2n+2. Various grades of such a copolymer are commercially available from the Amoco Corporation and are sold under the trade mark "INDOPOL". Any of these grades may be used in the present invention, but preferably those with a viscosity less than 5000 SUS (measured at 38°C).

[0011] One example of a suitable isobutylene-butene copolymer has an average molecular weight of 563, a viscosity of 2441 SUS at 38°C, and a flash point of 141°C, and is sold under the tradename "Amoco Polybutene H-15". The amount of copolymer used in the present invention can range from about 1 part by weight to about 50 parts by weight. Preferably, the amount used is from about 2 parts by weight to about 36 parts by weight.

[0012] The term polybutene refers to either a polyisobutylene which is essentially pure, or the isobutylene-butene copolymer described above which may contain up to for instance about 5% of other polymers, such as 1-butene and 2-butene. The isobutylene-butene copolymer is preferred, as it is less susceptible to crystallisation at low temperatures, but similar properties can be obtained using the 99+% polyisobutylene. Mixtures of polyisobutylene and the isobutylene-butene copolymer may also be used.

[0013] The isobutylene-butene copolymer, or polyisobutylene, is desired because it provides the lubricity needed to obtain a good surface finish on soft metals such as aluminium.

[0014] The second constituent of the metalworking fluid is a polyether glycol. This can be uncarboxylated, but preferably it has a carboxylate functionality since we have found the carboxylated materials give better performance. The polyether glycol provides additional lubricating properties to the metalworking fluid. The polyether glycol acts as an extreme pressure additive which reduces tool wear when machining hard metals such as titanium. Thus it is possible to machine hard metals without the use of traditional chlorine, sulfur or phosphorous extreme pressure additives, eliminating the hydrogen embrittlement and disposal problems caused by these additives. The molecular weight of the polyether glycol preferably is in the range 500 to 10,000. Suitable polyether glycols are commercially available from the Olin Corporation under the trade mark "POLY-G".

[0015] One example of a suitable polyether glycol is the proprietary polyoxyalkylene glycol sold by Olin Corporation under the tradename POLY-G MLB-10X. This polyoxyalkylene glycol has a viscosity of 587 SUS (at 38°C) and a specific gravity of 1.066 at 25°C and has a carboxylate functionality which is acidic in nature.

[0016] The amount of polyether glycol used in the present invention can range from about 2 parts by weight to about 50 parts by weight. Preferably, the amount used is at least about 5 parts by weight, often up to about 36 parts by weight.

[0017] A third constituent of the metalworking fluid, if desired, may be one or more emulsifiers. Any suitable oil-in-water emulsifier may be used in the invention, alone or in combination with other emulsifiers, to promote the formation of a stable microemulsion.

[0018] Examples of suitable emulsifiers that may be used in the present invention include but are not limited to tall oil fatty acids, petroleum sulfonates, fatty acid amines, fatty acid alkanolamides and non-ionic, cationic, anionic or amphoteric surfactants.

[0019] The selected emulsifiers should completely emulsify the other constituents of the concentrate when mixed with water. The emulsifiers should also be capable of maintaining a stable emulsion during use.

[0020] The amount of emulsifier used in the concentrate is generally from about 5 parts by weight to about 160 parts by weight, preferably 5 to 60 parts.

[0021] Other conventional metalworking fluid additives may be added so long as they do not adversely affect the emulsion stability or lubricity of the fluid. Such additives include corrosion inhibitors, defoamers, biocides, surfactants, azeotropes, colorants or dyes and pH buffering agents. However, since it is an advantage of the invention that extreme pressure additives (for instance sulphur, chlorine or phosphorous) are unnecessary, the compositions are preferably free of such additives.

[0022] Examples of suitable corrosion inhibitors include, but are not limited to, amine carboxylates and amine borate esters. Other suitable corrosion inhibitors would be obvious to one skilled in the art and are commercially available.

[0023] The amount of corrosion inhibitor is generally from about .1 part by weight to about 20 parts by weight, and preferably from about .1 parts by weight to about 15 parts by weight in the concentrate.

[0024] Suitable defoamers may be used in the present invention. Such defoamers are generally proprietary products and are known only by their commercial trade names. Suitable, preferably organic, defoamers for use in the present invention include TROYKYD D666, a proprietory blend available from Troy Chemical, and Foam Ban MS-455 from Ultra Additives. Other suitable defoamers would be obvious to one skilled in the art.

[0025] The amount of defoamer is generally from about 0.25 parts by weight to about 10 parts by weight, and preferably from about 0.5 parts by weight to about 5 parts by weight.

[0026] Compositions containing isobutylene-butene copolymer, polyether glycol having a carboxylate functionality, a corrosion inhibitor and a defoamer are particularly preferred.

[0027] The concentrate may be formed in any conventional manner such as adding all of the ingredients simultaneously and mixing them until a completely blended liquid is formed. However, it is preferred to first add the isobutylene-butene copolymer, or polyisobutylene, to a large mixer, then slowly add the one or more emulsifiers and then the corrosion inhibiting agent and polyether glycol, mixing well after each addition. Lastly, any other ingredients such as a defoamer and dye are added and thoroughly mixed into a homogeneous, stable blend. If desired, small amounts of water, may be added subsequent to mixing. The concentrate is then decanted into containers for storage and shipment.

[0028] The metalworking fluid may be used in its neat form, i.e., as a concentrate or it may be diluted.

[0029] Preferably, the metalworking fluid is diluted with water such that the amount of concentrate is from about 1% to 50% by volume of the total volume of the water and concentrate. However, in applications where water cannot be tolerated, a 100% solids concentrate can be used.

[0030] For example, where lubricity properties are most desired, less water is used so that there is more concentrate present. When cooling properties are most desired, the volume of water is greater than the volume of concentrate. Generally, where lubricity is primarily required, the amount of water used is about 50% by total volume. Where cooling is primarily required, the amount of water is from about 80% to 99% by total volume. Often the amount of water is below about 95% of the total volume.

[0031] The metalworking fluid is useful on a variety of metals including but not limited to steel, iron, aluminium, copper, titanium, nickel and alloys thereof. The fluid is of particular value for providing lubrication and cooling during the working of both hard and soft metals and for preventing the build-up of residue on tooling and the metal being worked.

Example 1

[0032] A metalworking fluid concentrate of the following formula was mixed together:
4.5 parts by weight of an isobutylene-butene copolymer;
6.0 parts by weight of a tall oil fatty acid low rosin emulsifier;
12.6 parts by weight of a petroleum sulfonate fatty acid amine blend emulsifier;
8.3 parts by weight of a fatty acid alkanolamide emulsifier;
7.5 parts by weight of polyoxyalkylene glycol, Olin Chemicals POLY-G MLB-10X (POLY-G is a trade mark);
0.1 parts by weight of a surfactant;
1.5 parts by weight of an amine carboxylate corrosion inhibitor;
1.3 parts by weight of an amine borate ester corrosion inhibitor;
1.0 parts by weight of a sodium salt of tolyltriazole corrosion inhibitor;
0.2 parts by weight of a citrus fragrance;
1.5 parts by weight of a glycol ether;
3.0 parts by weight of a biocide;
0.5 parts by weight of triethanolamine;
0.5 part by weight of a defoamer, Troy Chemicals Troykyd D666 (Troykyd is a trade mark); 0.5 of a second defoamer, Foam Ban MS-455 from Ultra Additives and, 0.06 part by weight of a blue dye.
51.0 deionised water (optional).

[0033] The fluid of Example 1 was used to machine hydraulic valve bodies from 2024 and 356 cast aluminiums and titanium using a carbide tool. A straight oil was used side by side with the fluid of Example 1 for comparison. Results were as follows:

Coolant Type	Straight Oil	Fluid of Example 1
Concentration	100%	11% concentration in water
Sump Life	2 Months	> 4 Months
Parts/Tool
Milling	500	1000+
Reaming	135	475+
Drilling	200	900+
Speed (SFM)
Milling	60	600
Reaming	30	490
Drilling	100	600-800
Finish (RMS)
Reaming	20-30	8-16

[0034] The metalworking fluid of Example 1 was usable for more than twice as long as the straight oil. This is due both to the greater thermal stability of the fluid of Example 1 and to its reduced susceptibility to contamination by metal fines. The number of parts which could be machined with a given tool was greatly increased. Higher speeds were also obtainable and the surface finish was improved.

[0035] While this invention has been discussed in the light of its preferred embodiments, i.e., as a metalworking fluid for the cutting of hard and soft metals, it is by no means meant to be so limited. The metalworking fluid of this invention may be used in any metalworking operation where its properties would be useful. Examples of such metalworking operations include but are not limited to tapping, grinding, milling and forming.

Claims

1. A metalworking fluid comprising a polybutene and a polyether glycol.

2. A fluid according to claim 1 wherein the polybutene is an isobutylene-butene copolymer, composed of 95-100% by weight of one or more mono-olefins and 0-5% by weight of one or more isoparaffins.

3. A fluid according to claim 1 wherein the polybutene is essentially all polyisobutylene.

4. A fluid according to any preceding claim wherein the polyether glycol has a carboxylate functionality.

5. A fluid according to any preceding claim wherein the polyether glycol is a polyoxyalkylene glycol.

6. A fluid according to claim 5 wherein the polyoxyalkylene glycol has acidic carboxylic functionality.

7. A fluid according to any preceding claim wherein the polybutene is from 2 to 50 parts by weight and the polyether glycol is from 2 to 50 parts by weight, preferably 5 to 36 parts.

8. A fluid according to any preceding claim further comprising from 5 to 160, preferably 5 to 60, parts by weight of one or more emulsifiers and that is an emulsifiable blend.

9. A fluid according to claim 8 wherein the emulsifier is selected from sulfonates, non-ionic, cationic, amphoteric and anionic surfactants, and is preferably a fatty acid alkanolamide.

10. A fluid according to claim 8 or claim 9 further comprising water in an amount of from 1% to 99%, preferably 50 to 99%, by volume of the total volume.

11. A fluid according to any preceding claim further comprising from 1 to 20 parts of one or more corrosion inhibitors.

12. A fluid according to any preceding claim further comprising from 0.5 to 15 parts of an organic defoamer.

13. A fluid according to any preceding claim and that is free of extreme pressure additives.

14. A method of metalworking comprising applying to a metal surface a metalworking fluid composition according to any preceding claim and performing a metalworking operation on the metal surface.

15. A method according to claim 14 wherein the metal surface is selected from steel, iron, aluminium, copper, titanium, nickel, and alloys thereof.