Defoaming agent composition for lubricating oil and method of defoaming using this

Abstract

The present invention provides a defoaming agent composition in gel form, of number 1 NLGI grade or harder, for application to the inside wall of a container, being a composition for defoaming bubbles generated from lubricating oil present within a container. The present invention further provides a method of defoaming lubricating oil characterized in that it includes a step of applying a defoaming agent composition in gel form, of number 1 NLGI grade or harder, to the inside wall of a container for lubricating oil and characterized in that this step is a step in which said defoaming agent composition is applied to the inside wall face at or above the oil surface of the lubricating oil, or higher than this.

Claims

1. A method comprising: applying a defoaming agent composition in gel form, of number 1 NLGI grade or harder, to the inside wall face of a container for a lubricating oil; and wherein the defoaming agent composition is applied to the inside wall face of the container at or above an oil surface of the lubricating oil; wherein foam produced during foaming of the lubricating oil elevates the oil surface of the lubricating oil; wherein the foam contacts the defoaming agent composition applied to the inside of the wall face of the container so as to mix the lubricating oil with the defoaming agent composition; and wherein the defoaming agent composition defoams the lubricating oil.

2. The method of claim 1 wherein the container is a gearbox.

3. The method of claim 1 wherein the defoaming agent composition is a fluorine-based defoaming agent composition.

4. The method of claim 1 wherein the defoaming agent composition is a fluorine-based grease comprising a base oil and a thickener.

5. The method of claim 4 wherein the base oil is a fluorine oil.

6. The method of claim 5 wherein the fluorine oil is selected from the group consisting of: a perfluoropolyether oil, a perfluoroalkyl ether oil, a low polymer of chlorotrifluoroethylene oil, a fluorine-modified silicone, and a combination thereof.

7. The method of claim 4 wherein the thickener comprises tricalcium phosphate.

8. The method of claim 1 wherein the defoaming agent composition has a number 1 NLGI grade.

9. The method of claim 1 wherein the defoaming agent composition has a number 2 NLGI grade.

10. The method of claim 1 wherein the defoaming agent composition has a number 3 NLGI grade.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a diagram of equipment employed in a practical example of the present invention and in a comparative example.

DETAILED DESCRIPTION OF THE INVENTION

(2) While the present invention is described in detail below, the invention is not restricted in any way to such specific applications, and can of course be applied to a wide range of applications that may be selected at will. It should be noted that although, hereinbelow, a fluorine-based defoaming composition is taken as an example of a defoaming composition since it has excellent defoaming performance, there is no restriction to this and the present invention could be applied to other defoaming agent compositions (such as for example silicone-based defoaming agent compositions).

(3) The present practical example relates to a defoaming agent composition of gel form which is of number 1 NLGI grade or harder, for applying to the inside wall of a container for lubricating oil. It further relates to a method of defoaming lubricating oil characterised in that this defoaming agent composition is employed. Such a defoaming agent composition necessarily includes a defoaming constituent and base oil, and may include a thickener. However, these terms merely refer to the functionality and do not necessarily imply chemically different constituents. Specifically, if for example a given constituent functions as both a defoaming constituent and a base oil, such a constituent constitutes both a defoaming constituent and a base oil. First of all, we shall describe a defoaming agent composition (constituents and properties) that is used as an active constituent and will then describe the method of its use.

(4) Fluorine-Based Defoaming Agent Composition Constituents

(5) Although the defoaming agent composition according to the present invention is not restricted to fluorine-based defoaming agent compositions, a fluorine-based defoaming agent composition will now be described. A fluorine-based defoaming agent composition contains a constituent (defoaming constituent) that contains a fluorine atom. Examples of defoaming constituents that may be used include: partially or completely fluorinated alkanes (for example perfluoroalkanes); partially or completely fluorinated alkyl ethers (for example perfluoroalkyl ethers); fluorine-modified silicones (fluorosilicone oils); or perfluoroalkyl-containing oligomers and perfluoroalkyl ethylene oxide adducts. A fluorine-based grease is described below as a preferred fluorine-based defoaming agent composition.

(6) Fluorine-Based Grease

(7) The fluorine-based grease of the preferred example is a gel-form composition comprising a base oil and thickener (which may contain additives), and indicates a lubricating oil employing a compound containing fluorine in at least part of the base oil, thickener and/or additives. As the fluorine-based grease, grease whose base oil is a fluorine oil is preferable: there may be mentioned by way of example a mode in which the base oil is the defoaming constituent (i.e. a fluorine oil (fluorine-based organic solvent) of the defoaming constituents referred to above, such as for example a perfluoropolyether (PFPE oil), perfluoroalkyl ether (PFAE oil), a low polymer of chlorotrifluoroethylene (CTFE oil), or fluorine-modified silicone), or a mode in which the thickener is the defoaming constituent (for example polytetrafluoroethylene (PTFE)). This grease is obtained by suitably adjusting the NLGI grade by addition of a freely selectable amount of thickener (such as for example tricalcium phosphate) or additive to a fluorine-based base oil (fluorine oil), or by adjusting the NLGI grade by addition of a fluorine-based thickener or additive to a freely selectable base oil. Also, there may be mentioned by way of example the CaP fluorine oil grease disclosed in Collected Papers submitted to the Petroleum Products Discussion Forum (Sekiyu Seihin Toron Kai) 2009 P107-110 Heat resistant grease employing tricalcium phosphate as a thickener. Of such greases, the CaP fluorine oil grease described above, specifically, a grease in which fluorine oil is selected as the base oil and tricalcium phosphate is selected as the thickener, is particularly suitable.

(8) Properties of Defoaming Agent Composition

(9) Grease of number 1 NLGI grade or harder (up to grade number 4, though no particular upper limit is specified) that is employed in the gel-form defoaming agent composition according to the present embodiment is suitable: more preferably the grease may be of number 2 or number 3 grade. If the NLGI grade is softer than number 0, it may be surmised that the grease might flow downwards over a long period of use, which would be undesirable. The method of determination of the NLGI grade is as set out in JIS K2220.

(10) There is no particular restriction regarding the form of the gel-form composition, and this may be for example a grease, cream or ointment. For example, if the gel-form composition is a grease, the dynamic viscosity of the base oil may be in the range of from 5 to 60 mm.sup.2/s at 100 C., preferably in the range of from 10 to 50 mm.sup.2/s. The dynamic viscosity at 100 C. may be determined in accordance with JIS K2283. It may be surmised that if the dynamic viscosity becomes too low, oil separation may tend to occur, lowering the retention of the defoaming constituent, or facilitating detachment of the defoaming agent composition, with consequent diminution or loss of the defoaming effect. On the other hand, if the dynamic viscosity is too high, it may be surmised that the defoaming constituent may not be properly dispersed in the oil, with the result that it cannot function as a defoaming agent.

(11) Method of Use

(12) The method of use according to the present embodiment includes a step of applying the gel-form defoaming agent composition described above to the inside wall of the container for lubricating oil. Specifically, this differs from the conventional technique of adding the defoaming agent to the lubricating oil. However, this may be combined with the conventional technique of adding the defoaming agent to the lubricant (in this case, if the amount of foaming is increased due to insufficiency of the defoaming agent as a result of capture by the filter or the like, such foaming is suppressed by deployment of the defoaming constituent into the oil from the defoaming agent composition that was applied in gel form). Hereinbelow, first of all, a case of application of the above method will be described; next, the aforementioned step in this method will be described.

(13) Case of Application to a Container

(14) There is no particular restriction as to the containers that may be employed in the present embodiment and for example gearboxes for automobiles or motorbikes (such as for example a manual gearbox, automatic gearbox, or EV reduction gear) may be mentioned by way of example; in particular, this embodiment may be suitably applied to gearboxes for AT use or CVT use. In gearboxes for AT use or CVT use, foaming occurs when lubricating oil is circulated within the container using the hydraulic pump, but, by applying the present embodiment, problems such as poor lubrication and loss of controllability of the device as a result can be prevented.

(15) Case of Application to Lubricating Oil

(16) There is no particular restriction regarding the lubricating oil to which the present embodiment may be applied. For example, as the base oil for the lubricating oil, there may be mentioned mineral oils called highly refined base oil, synthetic oils or mixtures of these (for example, base oils belonging to Group 1, Group 2, Group 3, Group 4 or Group 5 in the base oil category of the API (American Petroleum Institute), either alone or in the form of a mixture thereof). Also, there is no particular restriction to the content of base oil in the lubricating oil and this may be for example at least 60 weight % based on the total amount of the lubricating oil composition, preferably at least 70 weight %, more preferably at least 80 weight % and even more preferably at least 90 weight %.

(17) Application Step

(18) The application step according to the present embodiment is implemented by application of the defoaming agent composition to the inside wall of the lubricating oil container (i.e. the side portion thereof or a component such as for example a breather tube or oil gauge that is installed at a position higher than the oil surface of the container). Suitably, the defoaming agent composition is applied at or above the surface of the lubricating oil, or a position higher than this. The assumption in this case is that a defoaming action is unnecessary unless foaming of the lubricating oil occurs. In other words, foaming of the lubricating oil elevates the oil surface, enabling the foam to reach the location of application of the defoaming agent composition and contact of the foam and the defoaming agent composition thus constitutes the mechanism of the action whereby the defoaming constituent is mixed with the lubricating oil. By this arrangement, it becomes possible to prevent the defoaming constituent from being washed off from the inside wall side section of the container in a short time due to continued contact between the lubricating oil and the defoaming constituent. It should be noted that there is no particular restriction as regards the technique whereby application is effective and this could be achieved for example by coating or spraying.

EXAMPLES

(19) While the present invention is described below with reference to examples and comparative examples, the present invention is not restricted to the following.

Example 1

(20) About 0.03 g of grease (CaP fluorine oil grease: white colour, NLGI grade number 2, base oil dynamic viscosity (100 C.): 40 mm.sup.2/s) containing perfluoropolyether as a fluorine-based defoaming agent composition was applied to the inside face of the test container by the procedure set out below. The base oil of the grease used in this case is perfluoroether and the thickener is tricalcium phosphate.

Comparative Example 1

(21) About 0.03 g of defoaming agent composition constituted by high vacuum silicone grease from Dow Corning Inc. was applied to the inside face of the test container by the procedure set out below. The NLGI grade of this composition was number 0.

Comparative Example 2

(22) About 0.03 g of defoaming agent composition constituted by SH 200-100,000 cSt from Toray/Dow Corning Silicone Inc. was applied to the inside face of the test container by the procedure set out below (example of use of extremely high-viscosity silicone oil). The 25 C. dynamic viscosity of this composition was 100,000 mm.sup.2/s.

(23) Defoaming Test

(24) A foaming test was conducted using the equipment of the diagram shown in FIG. 1. An evaluation was conducted by the following method, to evaluate the amount of foaming, using a homogeniser (20).

(25) Equipment Used

(26) Homogeniser (20): IKA Labortechnik Ultra-Turaax T25

(27) Generator shaft (22): S-25N-25F (manufactured by the same company as the homogeniser referred to above)

(28) Cylinders (24): made of glass, height 20 to 160 mm (1 mm each), graduated, internal diameter 36 mm, thickness 2 mm, height 200 mm

(29) Heater (26): heater having sufficient electrical capacity to heat the oil to a temperature of 140 C. when oil was introduced into the aforementioned cylinders (24)

(30) Thermocouple (28): capable of measurement from 80 C. to 140 C. at 10 C. intervals

(31) Reference Oil

(32) As reference oil (lubricating oil), the oil: Shell ATF manufactured by Showa Shell Sekiyu Ltd, excluding the defoaming agent, was employed.

(33) Preparation for Measurement

(34) 1. 62.5 mL volume of the samples prepared in Example 1, Comparative Example 1 or Comparative Example 2 was taken (55 mm on the graduated scale).

(35) 2. The equipment was set up as shown in the diagram.

(36) 3. The positions of the homogenisers (20) were matched. Specifically, the positions of the holes on the shafts were matched with the 50 to 60 mm positions of the cylinders (24) (oil surface 65 to 66 mm at room temperature). At this point, the distance of the tip of the shaft from the bottom of the container was in the vicinity of 20 mm.
4. The homogenisers (20) were rotated at 8000 rpm, and the oil was heated by the heaters up to the measurement temperature.
Method of Applying the Defoaming Agent Composition

(37) The test device was set in position on the stirring shaft (outer) and the defoaming agent composition was then applied with an injector at a position of 90 to 95 mm (the volume when foaming of the reference oil occurred was 117 mm, so the aforementioned position was set so as to make it possible to ascertain the defoaming capability).

(38) Measurement Sequence

(39) 1. The position of the oil surface (prior to stirring) at the measurement temperature (120 C.) was recorded, in a condition with the homogeniser (20) stopped.

(40) 2. The homogeniser (20) was rotated at 8000 rpm, and the heater output was readjusted to the measurement temperature.

(41) 3. When the measurement temperature had been reached, rotation of the homogeniser (20) at 20,000 rpm was commenced.

(42) 4. After stirring for 1 min, keeping the homogeniser (20) rotating, the position of the oil surface and the height of the surface of the foam were recorded (oil surface position after 1 min of stirring). The amount of foaming (mm) was obtained by calculation from reading of the surface of the foam after stirring)(reading of the oil surface prior to stirring).
Test Results
The test results are shown in Table 1.

(43) TABLE-US-00001 TABLE 1 Comparative Comparative Example 1 Example 1 Example 2 Position of oil surface prior to stirring 71 mm 69 mm 70 mm Application 1 min after Position of oil 91 mm 127 mm 118 mm stirring surface Amount of foaming 20 mm 58 mm 48 mm No stirring 1 min after Position of oil 118 mm 115 mm 118 mm stirring surface Amount of foaming 47 mm 46 mm 48 mm Degree of increase/decrease of foam 57% +26% 0%

(44) In Example 1, on observing the inner circumference of the cylinder used for the foaming test, the phenomenon was ascertained that, when the foam that had been generated came into contact with the defoaming agent composition, defoaming occurred and further foaming did not take place. Furthermore, it was ascertained that the defoaming effect persisted even after the lapse of 1 min from the start of the test. It was surmised that the reason for continued manifestation of the excellent defoaming effect over a long period in this way was that, when the defoaming agent composition came into contact with the bubbles, these bubbles underwent partial collapse without experiencing excessive repulsion of the oil, and the perfluoropolyether, which possesses the defoaming effect, continued to be deployed in the oil to a suitable degree.

(45) In contrast, in Comparative Example 1, even though the bubbles that were generated came into contact with the defoaming agent composition, foaming still occurred without manifestation of a defoaming effect. After 1 min from the commencement of the test, the amount of foaming had in fact increased, compared with the situation in which no defoaming agent composition was applied; in other words, an effect that could be described as a foaming effect was identified: thus it was found that there was an effect that was the opposite of the effect intended in the present invention.

(46) Furthermore, in Comparative Example 2, the result was that the extent of increase/decrease of the foam was the same, irrespective of whether or not the defoaming agent composition had been applied: thus it was found that the defoaming agent composition manifested no defoaming effect.

(47) It was therefore found that the defoaming agent composition used in the present invention, by application to the inside wall above the oil surface, had a highly beneficial effect in suppressing the foaming that was originally generated, compared with the defoaming agent composition employed in Comparative Example 1 and Comparative Example 2.