Water / Glycol Based Hydraulic Fluid

Abstract

WATER / GLYCOL-BASED HYDRAULIC FLUID. The present invention provides a water / glycol-based hydraulic fluid comprising a total fatty acid and dimeric acid of more than 0.4 and not more than 1.2% by mass as a fatty acid lubricant, and also a phosphate ester between 0.01 and 0.07% by mass. The phosphate ester has the following structure (1): herein R1 and R2 each represent a hydrogen atom or a hydrogen group with a number of carbons between 1 and 30, and may be mutually identical or mutually different; R3 represents a hydrocarbon group with a number of carbons between 1 and 20; R4 represents a hydrogen atom or a hydrocarbon group with a number of carbons between 1 and 30; and X1, X2, X3 and X4 each indicate an oxygen atom or a sulfur atom, wherein these may be mutually identical or mutually different.

Description

"Water / Glycol-Based Hydraulic Fluid" FIELD OF THE INVENTION

[001] The present invention relates to an improvement of a water / glycol-based hydraulic fluid. BACKGROUND OF THE INVENTION

[002] Hydraulic equipment is not only widely used in industry, contributing to productivity, but has also been widely adopted in society in general. Hydraulic fluid is used as the power transmission medium in these hydraulic devices, where typically a petroleum-based hydraulic fluid that uses a mineral oil-based base oil, such as a highly refined paraffin-based base oil, is used as the hydraulic fluid.

[003] However, in machine equipment, such as iron fabrication or steel fabrication equipment in the steel industry, various types of hydraulic equipment, die casting machines, forging presses and the like, where fire prevention is required, and in hydraulic equipment in entertainment devices, stage equipment, and the like, in indoor installations that must emphasize fire safety, petroleum-based hydraulic fluids cannot be used, but water / glycol-based hydraulic fluids, which are fluids that include flame-retardant water, are used.

[004] When using such water / glycol-based hydraulic fluid, which is a fluid that includes water, it is important that the hydraulic actuation is carried out smoothly and that a long service life is achieved for the hydraulic equipment and, therefore, it is necessary to have good wear resistance and lubricity.

[005] There are known hydraulic compositions including water that include, for example, a polyoxyethylene alkylene glycol diether compound, a polyoxyalkylene glycol monoether compound, a polyoxypropylene glycol monoether compound and a fatty acid salt, of a specific structure, in water, Petition 870220089538, dated 09 / 29 / 2022, page 15 / 26 2 / 10 in order to cause an improvement in lubricity and wear resistance performance in water / glycol-based hydraulic fluid, for example, in JP3233490.

[006] Furthermore, the inclusion of a small amount of a neutralization product of a base and glycerol borate, which is produced by the reaction of, for example, boric anhydride or boron trichloride, in a water / glycol-based hydraulic fluid is known in JP 2646308.

[007] In addition, the inclusion of a water-soluble polyether of a specific structure derived from water-soluble polyoxyalkylene polyols and glycidyl ether in a water / glycol-based hydraulic fluid is also known from JP H7-233391. SUMMARY OF THE INVENTION

[008] The present invention produces a high-performance water / glycol-based hydraulic fluid by greatly improving its wear durability, without any negative effect on various types of water / glycol-based hydraulic fluid performance, by mixing specific additives into the water / glycol-based hydraulic fluid.

[009] The water / glycol-based hydraulic fluid of the invention comprises, in a total of 100% by mass, water between 20 and 60% by mass, glycols between 20 and 60% by mass, and a fatty acid-based lubricant, an alkaline hydroxide compound, a thickening agent, a rust inhibitor, a corrosion inhibitor, an antifoaming agent, and the like. During the research and development carried out by the present inventors with the aim of improving the performance of water / glycol-based hydraulic fluids, as described above, it was discovered that it is possible to considerably improve the wear resistance of a water / glycol-based hydraulic fluid through the use of dimeric acid and lauric acid as fatty acid lubricants, together with the inclusion of a phosphate ester of specific structure, and the present invention was created based on this knowledge. Petition 870220089538, dated 09 / 29 / 2022, page 16 / 26 3 / 10

[010] That is, the present invention is a water / glycol-based hydraulic fluid which includes a total of dimeric acid and fatty acid of more than 0.4% by mass and not more than 1.2% by mass, and also a phosphate ester, wherein the phosphate ester has the following structure (1): R-X1 / X3\ Λ3O XII R2—X2X4--R3^lOR4(1)

[011] wherein each R1 and R2 represent a hydrogen atom or a hydrogen group with a number of carbons between 1 and 30 and may be mutually identical or mutually different; R3 represents a hydrocarbon group with a number of carbons between 1 and 20; R4 represents a hydrogen atom or a hydrocarbon group with a number of carbons between 1 and 30; and X1, X2, X3 and X4 each indicate an oxygen atom or a sulfur atom, which may be mutually identical or mutually different. DETAILED DESCRIPTION OF THE INVENTION

[012] The present invention allows the easy production of a water / glycol-based hydraulic fluid with good convenience, with considerably improved wear resistance, without any negative effect on various types of water / glycol-based hydraulic fluid performance, by mixing in small quantities the specific additives described above.

[013] A fatty acid lubricant is used in the water / glycol-based hydraulic fluid according to the present invention. The fatty acid lubricant may be, for example, capric acid, undecyl acid, lauric acid, tridecyl acid, myristic acid, pentadecyl acid, palmitic acid, margaric acid, stearic acid or other saturated fatty acid, oleic acid, linoleic acid, linolenic acid, or other unsaturated fatty acid, or similar. In addition, dimeric acid, which is a dimer of unsaturated fatty acids with 18 carbons, is also included. A dimeric acid is a liquid fatty acid that includes monobasic and tribasic acids and has, as Petition 870220089538, dated 09 / 29 / 2022, pp. 17 / 26 4 / 10 main component, a C36 dibasic dicarboxylic acid produced by dimerization from a C18 unsaturated fatty acid, which has vegetable fat or oil as its raw material.

[014] Fatty acid and dimeric acid are included in the total in more than 0.4% by mass and not more than 1.2% by mass in relation to the total composition of the water / glycol-based hydraulic fluid, and preferably between 0.6 and 1.1% by mass, and more preferably between 0.8 and 1.0% by mass.

[015] If the inclusion ratio described above were less than 0.4% by mass, it would not be possible to produce adequate wear resistance, while, on the other hand, if in excess of 1.2% by mass, there would be a tendency to produce sludge, which would be undesirable.

[016] Furthermore, although the fatty acids described above normally use the acid form, the one formed into a sodium salt can also be used, and both of the above can be mixed for use as appropriate.

[017] In addition, a phosphate ester is included in this water / glycol-based hydraulic fluid.

[018] The phosphate ester is represented by the following general formula (1): R1-X1 / X3\ / / 3 PzR2-X2 V R3-W-OR4 (1)

[019] In this general formula, Ri and R2 are each a hydrogen atom or a hydrocarbon group with a number of carbons between 1 and 30, where Ri and R2 can be mutually identical or can be mutually different.

[020] R3 above represents a hydrocarbon group with a number of carbons between 1 and 20. R4 represents a hydrogen atom or a hydrocarbon group with a number of carbons between 1 and 30. X1, X2, X3 and X4 are each an oxygen atom or a sulfur atom and may be mutually identical or may be mutually different. Petition 870220089538, dated 09 / 29 / 2022, page 18 / 26 5 / 10

[021] This phosphate ester is included between 0.01 and 0.07% by mass, in relation to the total water / glycol-based hydraulic composition, but preferably uses between 0.01 and 0.05% by mass, and more preferably between 0.015 and 0.03% by mass.

[022] If the inclusion ratio were less than 0.01% by mass, the effect of the addition to produce adequate wear resistance would not be produced, which would be undesirable.

[023] Glycol can be, for example, ethylene glycol, propylene glycol, butylene glycol, hexylene glycol, diethylene glycol, dipropylene glycol, dibutylene glycol, dihexylene glycol, trimethylene glycol, triethylene glycol, triprethylene glycol or similar.

[024] Glycol can be used in a single variety alone or two or more types can be mixed for use. Preferably, propylene glycol or dipropylene glycol is used. This glycol is used between 20 and 60% by mass, relative to the total composition of water / glycol-based hydraulic fluid, and more preferably used between 30 and 50% by mass.

[025] An alkanolamine can be used as a rust inhibitor. Alkanolamines can be, for example, methanolamine, ethanolamine, propanolamine, diethanolamine, triethanolamine, dimethylethanolamine, N-methylethanolamine, N-methyldiethanolamine, N,N-dimethylaminoethanol, N,N-diethylaminoethanol, N,N-dipropylaminoethanol, N,N-dibutylaminoethanol, N,N-dipentylaminoethanol, N,N-dihexylaminoethanol, N,N-diheptylaminoethanol, N,N-dioctylaminoethanol or similar. This alkanolamine is included between 1.0 and 5.0% by mass in relation to the total composition.

[026] The alkaline hydroxide compound is potassium hydroxide or sodium hydroxide, either of which may be used alone or, as appropriate, both may be used together. The alkaline hydroxide is included between 0.01 and 0.12% by mass relative to the total composition, and more Petition 870220089538, dated 09 / 29 / 2022, pp. 19 / 26 6 / 10 preferably included between 0.04 and 0.06% by mass.

[027] In addition, as needed, publicly known additives, for example, thickening agents, lubricating agents, metal stabilizing agents, wear inhibitors, extreme pressure agents, dispersing agents, metal-based cleaning agents, friction adjusting agents, corrosion inhibitors, anti-emulsifying agents, anti-foaming agents and other various types of additives may be mixed, individually or in combinations thereof, in such water / glycol-based hydraulic fluid. In this case, an additive package for water / glycol-based hydraulic fluid may be used. EXAMPLES

[028] The water / glycol-based hydraulic fluid according to the present invention will be explained in detail below, citing embodiments and reference examples; however, the present invention is in no way limited by it.

[029] The water / glycol-based hydraulic fluids of Examples 1 to 3 were produced by mixing the various components based on the mixing amounts given in Table 1. EXAMPLE 1

[030] A water / glycol-based hydraulic fluid was produced by using 0.400% by mass of dimeric acid, 0.400% by mass of lauric acid as fatty acid, 0.015% by mass of 3-(di-isobutoxy-thiophosphorylsulfanyl)-2-methylpropionic acid as a phosphate ester (A), 38.628% by mass of propylene glycol as glycol, 16.10% by mass of water-soluble polymer as thickening agent, 2.565% by mass of total inclusion of sodium hydroxide, corrosion inhibitors, antifoaming agents and the like, as other additives, and 41.892% by mass of water and mixing thoroughly. The water / glycol-based hydraulic fluid had a preliminary alkalinity, produced according to JIS K 2234-1994, of 20, a kinematic viscosity at 40 °C of 46 mm2 / s and a pH of 11. Petition 870220089538, dated 09 / 29 / 2022, page 20 / 26 7 / 10

[031] The phosphate ester (A) used in Example 1, shown above, is the one represented by the following structural formula: h9c4—O\ θ zp / II H9c4—O 's---CH(CH3)—U— OH EXAMPLE 2

[032] A water / glycol-based hydraulic fluid was produced by using 0.400% by mass of dimeric acid, 0.400% by mass of lauric acid as a fatty acid, 0.015% by mass of ethyl-3(bis(1-methylethoxy)phosphinothioyl)thiol)propionate as a phosphate ester (B), 38.628% by mass of glycol, 16.10% by mass of thickening agent, 2.565% by mass of other additives and 41.892% by mass of water and mixing thoroughly. The water / glycol-based hydraulic fluid had a preliminary alkalinity, produced by JIS K 2234-1994, of 20, and a kinematic viscosity at 40 °C of 46 mm2 / s.

[033] The phosphate ester (B) used in Example 2, shown above, is the one represented by the following structural formula (where R is an ethyl group). / H \ SI II CH3—C—O- -P—s—ch2—ch2— coor X CH3 / 2 EXAMPLE 3

[034] A water / glycol-based hydraulic fluid was produced by using 0.400% by mass of dimeric acid, 0.400% by mass of lauric acid as a fatty acid, 0.030% by mass of phosphate ester (B), 38.628% by mass of glycol, 16.10% by mass of thickening agent, 2.565% by mass of other additives and 41.877% by mass of water and mixing thoroughly. The preliminary alkalinity produced by JIS K 2234-1994 was 20, with a kinematic viscosity at 40 °C of 46 mm2 / s. Comparative Examples 1 to 5 Petition 870220089538, dated 09 / 29 / 2022, pp. 21 / 26 8 / 10

[035] The water / glycol-based hydraulic fluids were produced in the same manner as in the embodiments set out above by mixing several components based on the mixing amounts given in Table 2. All water / glycol-based hydraulic fluids of Comparative Examples 1 to 5 had preliminary alkalinities, produced by JIS K 2234-1994, of 20, and kinematic viscosities at 40 °C of 46 mm2 / s. TEST

[036] The following tests were performed to evaluate wear resistance and lubricity for the Examples and Comparative Examples presented above. FOUR-SPHERE SHELL TEST

[037] Based on ASTM D4172 standard, the operation was performed for 30 minutes at room temperature with a load of 40 kgf with a primary shaft rotation speed of up to 1,500 rpm, and the diameters of the wear mark (mm) on the steel balls were measured after the tests.

[038] Evaluation Standards:

[039] Diameter of wear mark < 0.65 mm: Approved (O)

[040] Diameter of wear mark > 0.65 mm: Failed (x) TEST RESULTS

[041] The test results are presented in Tables 1 and 2. Petition 870220089538, dated 09 / 29 / 2022, pages 22 / 26 9 / 10 TABLE 1 Example 1 Example 2 Example 3 Dimeric Acid 0.400 0.400 0.400 Lauric Acid 0.400 0.400 0.400 Phosphate Ester (A) 0.015 Phosphate Ester (B) 0.015 0.030 Glycol 38.628 38.628 38.628 Thickening Agent 16.100 16.100 16.100 Other Additives 2.565 2.565 2.565 Water 41.892 41.892 41.877 Wear Mark Diameter (mm) 0.47 0.57 0.52 0

[042] As can be seen in Table 1, in Example 1, where 0.40 wt% of dimeric acid and 0.40 wt% of lauric acid were used together (for a total of 0.80 wt%) and 0.015 wt% of phosphate ester (A) was used, the wear mark diameter after completion of the four-shell ball test was small, at 0.47 mm, indicating excellent wear resistance and lubricity.

[043] In Example 2, the same amount of phosphate ester (B) was used instead of phosphate ester (A) from Example 1, and the wear mark diameter was 0.57 mm; this result was also satisfactory. In Example 3, the inclusion ratio of phosphate ester (B) was doubled compared to Example 2, and the wear mark diameter improved to 0.52 mm. TABLE 2 Comp. Example 1 Comp. Example 2 Example Comp. 3 Comp. Example 4 Comp. Example 5 Dimeric Acid 0.400 0.200 0.200 0.400 Lauric Acid 0.400 0.200 0.200 0.400 Phosphate Ester (A) 0.015 0.030 0.050 0.050 Glycol 38.628 38.628 38.628 38.628 38.628 Petition 870220089538, dated 09 / 29 / 2022, pp. 23 / 26 10 / 10 Comp. Example 1 Comp. Example 2 Example Comp. 3 Comp. Example 4 Comp. Example 5 Thickening Agent 16.100 16.100 16.100 16.100 16.100 Other Additives 2.565 2.565 2.565 2.565 2.565 Water 41.907 42.292 42.277 42.257 42.257 Wear Mark Diameter (mm) 0.72 X 0.78 X 0.85 X 0.87 X 0.88 X

[044] On the other hand, in Comparative Example 1, when there was no phosphate ester, the diameter of the wear mark after completion of the four-ball shell test was 0.72 mm, resulting in a failure, despite the use of dimeric acid and lauric acid.

[045] In Comparative Examples 2 and 3, no good effects were produced when the total amount of dimeric acid and lauric acid was low, despite the inclusion of the phosphate ester.

[046] Furthermore, in Comparative Examples 4 and 5, it is understood that no good effects are produced, despite increasing the phosphate ester to 0.05% by mass, if dimeric acid or lauric acid is absent.

Claims

1. Water / glycol-based hydraulic fluid, CHARACTERIZED in that it includes water between 20 and 60% by mass, glycol between 20 and 60% by mass, a fatty acid and a dimeric acid, wherein the total fatty acid and dimeric acid is more than 0.4% by mass and not more than 1.2% by mass as a fatty acid lubricant, and also a phosphate ester represented by the following general formula (1): R2-X2 X4 R3-U-OR4 (1) wherein Ri and R2 each represent a hydrogen atom or a hydrogen group with a number of carbons between 1 and 30, and may be mutually identical or mutually different; R3 is -CH(CH3)- or -CH2-CH2-; R4 represents a hydrogen atom or a hydrocarbon group with a number of carbons between 1 and 30; and where Xi and X2 of the phosphate ester are oxygen atoms and X3 and X4 are sulfur atoms.

2. Water / glycol-based hydraulic fluid, according to claim 1, CHARACTERIZED in that the phosphate ester inclusion ratio is between 0.01 and 0.07% by mass.

3. Water / glycol-based hydraulic fluid, according to claim 1, CHARACTERIZED in that the number of carbons in the fatty acid is between 6 and 18.