JP5388486B2 - Grease-like lubricant - Google Patents

Description

  The present invention relates to a grease-like lubricant suitably used for a sliding portion such as a core type run flat tire.

In recent years, there has been a demand from the market for a run-flat tire / wheel assembly (hereinafter referred to as a run-flat tire) that can travel safely over a certain distance even when the tire punctures and the tire internal pressure becomes zero. As one of the run flat tires, a core type run flat tire in which a synthetic resin or metal core is attached to a rim portion in the air chamber of the tire is known.
In the case of this core type run-flat tire, the inner peripheral surface of the tire and the core are in contact with each other during run-flat running, and heat is generated due to friction, and the inner peripheral surface of the tire and the core itself are worn to endure the run-flat tire. There is a problem that the performance is reduced and the travelable distance is reduced.

Therefore, a proposal has been made to reduce the friction between the tire inner peripheral surface and the core by arranging a lubricant between the tire inner peripheral surface and the core (see, for example, Patent Documents 1 and 2).
Among these, in Patent Document 1, by adding a volatile substance having a boiling point in a range of 60 ° C. to 90 ° C. to a grease-like lubricant, a portion that generates heat during run flat running in addition to lubrication performance by a lubricating component Is cooled by the heat of vaporization of volatile substances.
Patent Document 2 discloses that the inner surface of the tire (the inner surface of the crown portion) is coated with a silicone compound in which a metal oxide is added to dimethyl silicone oil or the like, thereby providing excellent retention on the inner surface of the crown portion and flame retardant. It is described that it has sex.

JP 2005-319834 A JP-A-6-270617

However, in the case of the technique described in Patent Document 1, since the amount of volatile substances in the lubricant is limited, the effect of suppressing heat generation cannot be sufficiently maintained. Also, in run-flat running on heavy-duty vehicles such as trucks, the friction between the tire inner peripheral surface and the core is stronger, so the lubrication performance is not sufficient with conventional lubricants, and the durability of run-flat tires ( There is a problem that the travelable distance) is still low.
The present invention has been made in view of the above problems, and an object of the present invention is to provide a grease-like lubricant that is excellent in lubricity and can be suitably applied to sliding parts such as run-flat tires.

As a result of intensive studies on the composition of the grease-like lubricant, the present inventors have combined polyalkylene glycol, which is a lubricating oil (base oil, base oil) that has not been mixed because of its low compatibility, with silicone oil. It has been found that the lubricity is remarkably improved.
That is, the grease-like lubricant of the present invention is based on polyalkylene glycol and dimethyl silicone oil, and further includes a soap thickener, a composite soap thickener, a urea thickener, an organic thickener, and saw including a thickening agent is at least one selected from the group of inorganic thickeners, the mass ratio represented by (the dimethyl silicone oil / said polyalkylene glycol), 10 / 90-40 / 60, Or it is the grease-like lubricant for run flat tires within the range of 60/40 to 90/10.

  The grease-like lubricant of the present invention can be suitably used for a sliding portion, and can be particularly suitably used for a core type run flat tire.

  According to the present invention, it is possible to obtain a grease-like lubricant that is excellent in lubricity and can be suitably applied to a sliding portion such as a core type run-flat tire.

  Hereinafter, embodiments of the present invention will be described. The grease-like lubricant of the present invention is based on polyalkylene glycol and silicone oil, and further contains a thickener.

<Base oil>
A mixture of polyalkylene glycol and silicone oil is used as the base oil. It has been found that the lubricity is remarkably improved by combining a polyalkylene glycol, which is a lubricating oil (base oil, base oil) and a silicone oil, which have not been mixed because of their low compatibility.
The reason for this is not clear, but silicone oil has low surface tension and good wettability to the object to be lubricated (especially the tire inner surface (rubber)), while polyalkylene glycol has high surface tension, and the object to be lubricated (especially tire) It is inferior in wettability to the inner surface) but excellent in load resistance. Therefore, it is considered that the mixture of both has wettability and load resistance.

  In addition, polyalkylene glycol and silicone oil have low compatibility, and even if they are mixed, they do not form a uniform mixture and may be partially phase separated. However, if it is used as a grease-like lubricant, it does not matter if phase separation occurs unlike a liquid lubricant. This is because grease is considered to retain the base oil in the thickener structure (for example, fiber structure) in the first place, so that even if the base oils are partially separated, the mixed state can be maintained as the grease. is there.

The polyalkylene glycol is not particularly limited, and examples thereof include polyethylene glycol, polypropylene glycol, and glycerin. The type of polyalkylene glycol may be any of monool type, diol type, triol type, diether type, and ester type.
Although it does not restrict | limit especially as a silicone oil, For example, a dimethyl silicone oil and a methylphenyl silicone oil are mentioned. The type of silicone oil may be either straight silicone oil or modified silicone oil.

<Thickener>
A thickener is used to make the base oil into a (semi) solid grease.
Although it does not restrict | limit especially as a thickener, For example, at least 1 sort (s) chosen from the group of a soap type thickener, a composite soap type thickener, a urea type thickener, an organic type thickener, and an inorganic type thickener. Can be used.
Examples of the soap-based thickener include metal soaps (lithium soap, sodium soap, aluminum soap, calcium soap, barium soap, etc.) obtained by saponifying oils and fats and metal hydroxides. Examples of fats and oils include natural animal and vegetable oils such as beef tallow, palm oil and coconut oil; hydrogenated natural animal and vegetable oils such as castor hydrogenated oil; natural animal and vegetable oils and hydrogenated oils such as stearic acid are decomposed Carboxylic acids; dicarboxylic acids such as adipic acid and sebacic acid; dibasic acids; aromatic acids such as benzoic acid and salicylic acid; aromatic carboxylic acids; and synthetic fatty acids. Sodium, calcium, lithium, aluminum, barium etc. are mentioned as a metal seed | species used as a metal hydroxide.
The composite soap thickener is a composite soap obtained by saponifying a metal hydroxide and two or more types of oils and fats, and examples thereof include a lithium complex, an aluminum complex, a calcium complex, and a barium complex. In general, a composite soap thickener has a finer fiber structure than a normal soap thickener and is excellent in heat resistance. Examples of the lithium complex include a saponified mixture of a fatty acid and a dibasic acid and lithium hydroxide.

Examples of urea thickeners include diurea compounds such as aromatic diurea compounds, aliphatic diurea compounds, and alicyclic diurea compounds; triurea compounds; tetraurea compounds; and polyurea compounds.
Examples of the organic thickener include terephthalamates such as sodium terephthalamate; phthalocyanines such as copper phthalocyanine; polymers such as PTFE (polytetrafluoroethylene).
Examples of the inorganic thickener include bentonite, mica, and silica gel. However, as bentonite, organic bentonite (a bentonite modified with an ammonium cation) is used.

  The above thickeners can be used alone or as a mixture of two or more.

By mixing the base oil and the thickener, a (semi) solid grease-like lubricant retaining the base oil in the thickener structure (for example, fiber structure) is obtained. The grease-like lubricant is usually in a (semi) solid state, but flows when a frictional force is applied, and exhibits a lubricating function.
The total amount of components other than the base oil is preferably 30% by mass or less, and more preferably 20% by mass or less, based on the entire grease-like lubricant. Moreover, it is preferable that the compounding quantity of the said thickener is 10-20 mass% with respect to the whole grease-like lubricant.
The consistency of the obtained grease-like lubricant is not particularly limited, but the consistency at 25 ° C. is preferably 285 to 325.

The grease-like lubricant of the present invention is excellent in lubricity and can be suitably used for sliding parts such as core type run-flat tires.
FIG. 1 shows a radial cross-sectional view of a run-flat tire. The run flat tire 10 includes a wheel having a rim 6 (only the rim is shown), a tire 2 attached to the outer periphery of the rim 6, and an annular core 4 disposed in the inner chamber of the tire 2. The inner diameter of the core 4 is substantially the same as the outer diameter of the central portion of the rim 6 and is fitted to the outer periphery of the central portion of the rim 6. The core 4 has a hollow structure, the outer peripheral surface of the core 4 is substantially flat, and a central portion in the axial direction of the outer peripheral surface forms a recess with a reduced diameter, and a band 7 is wound around the recess.
When the run-flat tire 10 is punctured, the internal pressure of the tire 2 decreases, and the inner surface of the crown portion of the tire 2 comes into contact with the outer peripheral surface of the core 4. Accordingly, the grease-like lubricant of the present invention is applied to the inner surface of the crown portion as the lubricating layer 20, and / or the grease-like lubricant of the present invention is applied to the outer peripheral surface of the core 4 as the lubricating layer 21, thereby the inner surface of the crown portion. Friction due to sliding between the outer peripheral surface of the core and the core can be reduced, and the durability (travelable distance) of the run-flat tire can be improved.

In the above base oil, if the mass ratio represented by (silicone oil / polyalkylene glycol) is in the range of 10/90 to 40/60, or 60/40 to 90/10, the lubricity is improved. preferable.
When the mass ratio is less than 10/90, the base oil is mostly occupied by polyalkylene glycol, and the silicone oil is decreased, and the effect of improving lubricity may be insufficient. When the mass ratio exceeds 90/10, the base oil is mostly occupied by silicone oil, and the polyalkylene glycol is decreased, and the effect of improving lubricity may be insufficient.
When the mass ratio is 40/60 to 60/40, the amounts of polyalkylene glycol and silicone oil are almost the same (= 50/50), and the cause is unknown, but the effect of improving lubricity is insufficient. There is.

The grease-like lubricant of the present invention may further contain a solid lubricant.
As the solid lubricant, inorganic lubricants having a layered crystal structure such as molybdenum disulfide, tungsten disulfide, antimony sulfide, graphite, fluorinated graphite, mica, boron nitride; soft such as copper, nickel, lead, tin, silver Metals: Metal salts such as metal borates and metal phosphates; Lubricating ceramics such as silicon nitride; Organic lubricants having a layered crystal structure such as melamine cyanurate (MCA) and organic molybdenum; Polytetrafluoroethylene (PTFE) ) And other polymers; polymers such as polyethylene, polypropylene, polyester, polyacetal, polycarbonate, polyamide, polyimide, high-density polyolefin, and polyester.
The above-mentioned solid lubricant can be used alone or as a mixture of two or more. Further, the solid lubricant can be powdered and dispersed and mixed in the grease-like lubricant of the present invention.
Moreover, it is preferable that the compounding quantity of the said solid lubricant is 10 mass% or less with respect to the whole grease-like lubricant.

The grease-like lubricant of the present invention may further contain other additives. Examples of such additives include known viscosity modifiers, antioxidants, metal deactivators, light stabilizers, rust inhibitors, structural stabilizers, corrosion inhibitors, hue stabilizers, and the like as grease additives. However, it is not limited to these.
Moreover, it is preferable that the total compounding quantity of the said additive is 1 mass% or less with respect to the whole grease-like lubricant.

As described above, the grease-like lubricant of the present invention can be produced by mixing the base oil and the thickener and further mixing the solid lubricant and various additives as necessary.
When using a soap-type thickener or a composite soap-type thickener as a thickener, a grease may be obtained by saponifying a metal hydroxide such as lithium hydroxide in the base oil. Existing metal soap may be added and saponified.
When a urea thickener, an organic thickener, or an inorganic thickener is used as the thickener, the base oil and these thickeners can be mixed and dispersed to obtain a grease.

  The present invention is not limited to the above embodiment. For example, as a base oil, in addition to a mixture of polyalkylene glycol and silicone oil, silicone oil and oil incompatible with this (polyalphaolefin (PAO), ester such as polyol ester, fluorine-based oil) are mixed. Things can be used.

EXAMPLES Hereinafter, although an Example demonstrates this invention further in full detail, this invention is not limited by these. Further, “parts” and “%” shown in the examples indicate parts by weight and% by weight unless otherwise specified.
<Manufacture of grease-like lubricant>
Dimethyl silicone oil, which is silicone oil as a base oil, and polyoxypropylene glycol monoalkyl ether, which is polyalkylene glycol (PAG), are mixed at a mass ratio shown in Table 1, and further a thickener (lithium soap) and a solid are mixed. A grease-like lubricant was produced by mixing and dispersing a lubricant (a mixture of PTFE, MCA, and calcium hydroxide) and an antioxidant.
The blending amount of the thickening agent was 10%, the blending amount of the solid lubricant was 10%, the blending amount of the antioxidant was 1%, and the balance was the base oil with respect to the entire grease-like lubricant.

<Evaluation of lubricity # 1>
Using a thrust friction and wear tester (model EFM-III-1020, manufactured by Oriental Co.), the test was performed with the RING ON DISK method. PC (polycarbonate) was used as the ring, and butyl rubber having a thickness of 2 mm (product number TIKM6507 from Tigers Polymer Co., Ltd.) was used as the disk.
After uniformly applying 0.2 g of the grease-like lubricant to the entire disk surface, the test was started by applying a load to the disk at a surface pressure of 1.25 MPa and a peripheral speed of 1 km / h (250 rpm). The test was terminated when the frictional resistance exceeded a predetermined upper limit, and the time at that time was defined as the durability time. However, the upper limit of the test was 120 minutes.
The obtained results are shown in Table 1.

<Evaluation of lubricity # 2>
Insert a resin core into a 13 × 8 1 / 2JJ wheel, prepare a run-flat wheel with a 265 / 45R13 tire assembled, and apply the grease-like lubricant (mixing ratio in Table 2) to the inner peripheral surface of the tire. This run flat tire was mounted on a 1.5 ton small truck and actually run. The tire traveled at a speed of 65 km / h at a tire internal pressure of approximately 0 Kpa, and the travel distance until the vehicle became unable to travel was measured.
The obtained results are shown in Table 2.

  As apparent from Tables 1 and 2, in the base oil, the mass ratio represented by (silicone oil / polyalkylene glycol) is within the range of 10/90 to 40/60, or 60/40 to 90/10. In this case, the durability by the thrust friction and wear test is 10 minutes or more, and the durability by the run-flat actual running test shows the same improvement in durability as the thrust friction and wear test, compared to the case where other blending ratios are used. It was found that durability was improved.

It is sectional drawing of the radial direction which shows an example of the core type run flat tire to which the grease-like lubricant of this invention is applied.

Explanation of symbols

2 Tire 4 Core 6 Rim 10 Run flat tire 20, 21 Lubricating layer with grease-like lubricant

Claims (2)

Base oil based on polyalkylene glycol and dimethyl silicone oil, selected from the group of soap-based thickeners, composite soap-based thickeners, urea-based thickeners, organic-based thickeners, and inorganic-based thickeners only contains the thickening agent is at least one,
A grease-like lubricant for run-flat tires, wherein the mass ratio represented by (the dimethyl silicone oil / the polyalkylene glycol) is in the range of 10/90 to 40/60, or 60/40 to 90/10 . The grease-like lubricant according to claim 1, further comprising a solid lubricant .

Images