Lubricant composition and lubricating oil composition containing said lubricant composition

Abstract

A lubricant composition containing a base oil and organic fine particles substantially consisting of the three elements of carbon, hydrogen and oxygen and having a proportion of particles having a particle diameter of 10 nm to 10 μm of 90% or greater, wherein the content of the organic fine particles is 0.01 to 50 parts by mass relative to 100 parts by mass of the base oil.

Claims

1. A lubricant composition, containing: a base oil; and organic fine particles substantially consisting of the three elements of carbon, hydrogen and oxygen and having a proportion of particles having a particle diameter of 150 nm to 5 μm of 90% or greater, wherein a content of the organic fine particles is 0.01 to 50 parts by mass relative to 100 parts by mass of the base oil, wherein the organic fine particles comprise a copolymer containing a unit (a) and a unit (b) as constituent units, and wherein a Hansen solubility parameter interaction distance between the base oil and the unit (a) is 5.2 to 6.2 (MPa).sup.1/2, and a Hansen solubility parameter interaction distance between the base oil and the unit (b) is 8.0 to 18.0 (MPa).sup.1/2, and wherein a weight average molecular weight of the copolymer is 1,000 to 500,000 and a compositional ratio of molar proportions of the unit (a) and the unit (b) is such that (a):(b) is 10 to 70:30 to 90, provided that the sum of the molar proportions is 100.

2. The lubricant composition according to claim 1, wherein a Hildebrand solubility parameter of the base oil is 15.0 to 18.0 (MPa).sup.1/2.

3. The lubricant composition according to claim 1, wherein the copolymer has a Hansen solubility parameter interaction distance from the base oil of 5.5 to 21.0 (MPa).sup.1/2.

4. A lubricating oil composition containing the lubricant composition according to claim 1.

5. The lubricating oil composition according to claim 4, further containing one or more selected from the group consisting of metal-based cleaning agents, ash-free dispersing agents, anti-wear agents, extreme pressure agents, antioxidants, viscosity index improving agents, pour point depressants, rust inhibitors, corrosion inhibitors, metal deactivators and anti-foaming agents.

Description

EXAMPLES

(1) The present invention will now be explained in greater detail through the use of examples, but is in no way limited to these examples.

(2) The Hansen solubility parameters (δ.sub.d, δ.sub.p and δ.sub.h) and Hildebrand solubility parameters (δ) of polymerizable monomers able to be advantageously used to synthesize organic fine particles that constitute the lubricant composition according to the present invention are shown in Table 3.

(3) TABLE-US-00003 TABLE 3 Solubility parameter Polymerizable (MPa).sup.1/2 monomer δ.sub.d δ.sub.p δ.sub.h δ Decyl acrylate 17.1 2.3 5.8 18.2 Lauryl acrylate 17.1 2.0 5.4 18.0 Cetyl acrylate 17.0 1.6 4.8 17.7 Stearyl acrylate 17.0 1.4 4.5 17.6 Hydroxyethyl 19.8 9.3 18.9 28.9 acrylate Methyl acrylate 17.9 7.6 10.4 22.0 Styrene 20.4 1.2 1.5 20.5

(4) Polymerizable Monomers Used Lauryl acrylate [constituent material of unit (a)] Hydroxyethyl acrylate [constituent material of unit (b-1)] Styrene [constituent material of unit (b-2)]

Production Example 1

(5) 44.1 g of a highly refined base oil (a hydrocarbon-based oil having 20 to 50 carbon atoms, viscosity index=112, δ.sub.d=16.3, δ.sub.p=0, δ.sub.h=0, δ=16.3) as a base oil and 21.8 g of butyl acetate were placed in a reaction vessel and heated to a temperature of 110° C. 174.0 g of lauryl acrylate and 22.0 g of hydroxyethyl acrylate as polymerizable monomers, 14.7 g of butyl acetate and 1.4 g of 2,2-azobisisobutyronitrile were added dropwise to the reaction vessel and stirred for a period of 2 hours. Next, while maintaining a temperature of 75° C. to 85° C., 284.1 g of styrene, 75.9 g of lauryl acrylate and 28.2 g of hydroxyethyl acrylate as polymerizable monomers and 5.2 g of 2,2-azobisisobutyronitrile were added dropwise and stirred for a period of 4 hours so as to bring about a polymerization reaction. Next, 344 g of a base oil was added and unreacted polymerizable monomers and butyl acetate were removed while increasing the temperature to 115° C. to 125° C., thereby preparing an organic fine particle-dispersed solution in which organic fine particles including a copolymer were dispersed in the base oil at a quantity of 50 parts by mass relative to the overall mass. The Hansen solubility parameter interaction distance between the base oil and the copolymer constituting these organic fine particles was 7.9 (MPa).sup.1/2, the Hansen solubility parameter interaction distance between the base oil and the unit (a) that constitutes this copolymer was 6.0 (MPa).sup.1/2, and the Hansen solubility parameter interaction distance between the base oil and the unit (b) was 11.0 (MPa).sup.1/2.

Production Example 2

(6) A solution (an organic fine particle-dispersed solution) in which a copolymer was completely dissolved in the base oil at a quantity of 50 parts by mass relative to the overall mass was prepared by altering the molar ratio of the constituent units in the manner shown in Table 4 below by altering the molar ratio of the polymerizable monomers used in Production Example 1. The Hansen solubility parameter interaction distance between the base oil and this copolymer was 9.4 (MPa).sup.1/2, the Hansen solubility parameter interaction distance between the base oil and the unit (a) that constitutes this copolymer was 6.0 (MPa).sup.1/2, and the Hansen solubility parameter interaction distance between the base oil and the unit (b) was 22.2 (MPa).sup.1/2.

(7) The particle size distribution of organic fine particles in the dispersed solutions prepared in Production Examples 1 and 2 was measured on a volume basis using a particle size distribution analyzer (an ELSZ-1000 available from Otsuka Electronics Co., Ltd.), and these results are also shown in Table 4. In addition, the molar ratios of polymerizable monomers used in the copolymers, the weight average molecular weights determined by means of GPC in terms of styrene, and the solubility parameters calculated using the Fedors method and the van Krevelen & Hoftyzer method are also shown in Table 4.

(8) TABLE-US-00004 TABLE 4 Production Production Example 1 Example 2 Constituent Compo- (a) 0.25 0.64 units sitional (b-1) 0.10 0.36 molar (b-2) 0.65 0 proportions Copolymer Weight average molecular weight 47000 250000 Solubility δ.sub.d 18.8 17.5 parameter δ.sub.p 1.25 2.2 (MPa).sup.1/2 δ.sub.h 6.08 8.9 δ 19.8 19.7 Lubricant Particle size <10 nm 0 Dissolved compo- distribution ≥10 nm, <50 nm 0 (measurement sition (%) ≥50 nm, <100 nm 0 not possible) ≥100 nm, <150 nm 0 ≥150 nm, <200 nm 0 ≥200 nm, <250 nm 0 ≥250 nm, <300 nm 14.3 ≥300 nm, <400 nm 23.3 ≥400 nm, <500 nm 32.0 ≥500 nm, <600 nm 18.2 ≥600 nm, <700 nm 8.2 ≥700 nm, <1000 nm 3.0 ≥1 μm, <5 μm 1.0 ≥5 μm, <10 μm 0 ≥10 μm 0

(9) <Evaluation of Friction Decrease Characteristics>

(10) Lubricant compositions containing a copolymer at a quantity of 0.5 mass % relative to 100 parts by mass of a base oil and containing a molybdenum dithiocarbamate at a quantity of 800 ppm in terms of molybdenum were produced by diluting the organic fine particle-dispersed solutions produced in Production Examples 1 and 2 with a base oil and then adding the molybdenum dithiocarbamate. A lubricant composition obtained using glycerin monooleate instead of the copolymers produced in Production Examples 1 and 2 (here, the glycerin monooleate completely dissolved in the base oil) and a lubricant composition containing no copolymer were produced as comparative examples.

(11) The coefficients of friction of these lubricant compositions were measured under the following test conditions using a frictional wear tester (HEIDEN TYPE: HHS2000, available from Shinto Scientific Co., Ltd.). The coefficient of friction is an average value for coefficient of friction obtained from 15 reciprocations prior to completion of the test. The test results are shown in Table 5.

(12) Test Conditions Load: 9.8 N Maximum contact pressure: 1.25×10.sup.−7 Pa Sliding speed: 5 mm/sec Amplitude: 20 mm Test number: 50 reciprocations Test temperature: 40° C. Sliding speed: 5 mm/sec Top plate: AC8A-T6 Bottom plate: SUJ2

(13) TABLE-US-00005 TABLE 5 Comparative Comparative Comparative Example 1 example 1 example 2 example 3 Organic fine Copolymer of Copolymer of Glycerin Not particles Production Production monooleate contained Example 1 Example 2 Coefficient 0.030 0.044 0.036 0.052 of friction

(14) The examples given above show that the lubricant composition according to the present invention achieves a high friction decrease effect by means of organic fine particles including a copolymer dispersed in the lubricant composition, and when the lubricant composition according to the present invention is used in combination with a molybdenum compound used in the past as a friction-reducing agent, it is understood that this advantageous effect is not impaired and it is possible to obtain a lubricant composition that exhibits a superior friction decrease effect in comparison with a case in which only a molybdenum compound is used.

Production Examples 3 to 11

(15) Organic fine particle-dispersed solutions were produced using a similar method to that used in Production Example 1, except that the molar ratios of the constituent units were altered in the manner shown in Table 6 by altering the molar ratios of the polymerizable monomers used and the reaction time was adjusted as appropriate. The weight average molecular weights, as determined by means of GPO in terms of styrene, of the copolymers constituting the organic fine particles, the solubility parameters calculated using the Fedors method and the van Krevelen & Hoftyzer method, and the Hansen solubility parameter interaction distances from the base oil are shown in Table 6. In addition, the particle size distribution of the organic fine particles in the organic fine particle-dispersed solutions was measured using the method described above, and these results are shown in Table 6.

(16) TABLE-US-00006 TABLE 6 Production Production Production Production Production Example 3 Example 4 Example 5 Example 6 Example 7 Constituent units Compositional molar (a) 0.25 0.59 0.44 0.44 0.60 proportions (b-1) 0.11 0.16 0.14 0.14 0.20 (b-2) 0.65 0.25 0.42 0.42 0.20 Copolymer Weight average molecular weight 38000 50000 115000 85000 63000 Solubility parameter δ.sub.d 18.80 17.68 18.08 18.08 17.64 (MPa).sup.1/2 δ.sub.p 1.27 17.50 1.56 1.56 1.83 δ.sub.h 6.17 6.89 6.69 6.69 7.35 δ 19.82 19.06 19.34 19.34 19.20 Hansen solubility Unit (a) to base oil 5.98 5.98 5.98 5.98 5.98 parameter Unit (b) to base oil 10.69 14.08 12.18 12.18 15.53 interaction Copolymer to base oil 8.04 7.63 7.74 7.74 8.04 distance Lubricant Particle size <10 nm 0 0 0 0 0 composition distribution (%) ≥10 nm, <50 nm 0 0 0 0 0 ≥50 nm, <100 nm 0 0 0 0 0 ≥100 nm, <150 nm 0 0 0 0 0 ≥150 nm, <200 nm 0 13.0 13.8 13.7 0 ≥200 nm, <250 nm 13.0 21.1 25.8 22.3 0 ≥250 nm, <300 nm 21.2 28.9 26.6 30.6 13.5 ≥300 nm, <400 nm 29.1 17.7 17.6 17.7 21.9 ≥400 nm, <500 nm 21.6 9.6 9.0 8.7 30.1 ≥500 nm, <600 nm 9.9 5.1 4.1 4.1 17.4 ≥600 nm, <700 nm 3.9 2.6 2.0 1.9 8.9 ≥700 nm, <1000 nm 0.9 1.2 0.8 0.8 4.5 ≥1 μm, <5 μm 0.2 0.8 0.3 0.1 3.8 ≥5 μm, <10 μm 0 0 0 0 0 ≥10 μm 0 0 0 0 0 Production Production Production Production Example 8 Example 9 Example 10 Example 11    Constituent units Compositional molar (a) 0.16 0.16 0.32 0.23 proportions (b-1) 0.04 0.09 0.00 0.00 (b-2) 0.80 0.75 0.68 0.77 Copolymer Weight average molecular weight 29000 50000 39000 36000 Solubility parameter δ.sub.d 19.28 19.25 18.56 18.94 (MPa).sup.1/2 δ.sub.p 1.06 1.15 1.25 1.12 δ.sub.h 4.55 5.72 4.14 3.73 δ 19.83 20.11 19.06 19.34 Hansen solubility Unit (a) to base oil 5.98 5.98 5.98 5.98 parameter Unit (b) to base oil 9.24 10.14 8.49 8.49 interaction Copolymer to base oil 7.57 8.29 6.25 6.58 distance Lubricant Particle size <10 nm 0 0 0 0 composition distribution (%) <10 nm, <50 nm 0 0 0 0 ≥50 nm, <100 nm 0 0 0 0 ≥100 nm, <150 nm 0 0 0 0 ≥150 nm, <200 nm 0 0 0 13.2 ≥200 nm, <250 nm 0 0 0 21.5 ≥250 nm, <300 nm 13.7 0 0 29.4 ≥300 nm, <400 nm 22.3 0 0 20.8 ≥400 nm, <500 nm 30.6 0 12.9 9.4 ≥500 nm, <600 nm 19.8 0 21.1 4.1 ≥600 nm, <700 nm 8.9 0 28.9 1.2 ≥700 nm, <1000 nm 3.6 14.3 19.2 0.4 ≥1 μm, <5 μm 1.1 85.7 17.8 0 ≥5 μm, <10 μm 0 0 0 0 ≥10 μm 0 0 0 0

Production Example 12

(17) An organic fine particle-dispersed solution was produced using a similar method to that used in Production Example 1, except that the molar ratios of the constituent units were altered in the manner shown in Table 7 by altering the molar ratios of the polymerizable monomers used and the reaction time was adjusted as appropriate. For the copolymer that constitutes the organic fine particles, the solubility parameters calculated using the Fedors method and the van Krevelen & Hoftyzer method and the Hansen solubility parameter interaction distances from the base oil are shown in Table 7. In addition, the particle size distribution of the organic fine particles in the organic fine particle-dispersed solution was measured using the method described above, and these results are shown Table 7.

(18) TABLE-US-00007 TABLE 7 Production Example 12 Constituent units Compositional (a) 0.25 molar (b-1) 0.38 proportions (b-2) 0.38 Copolymer Solubility δ.sub.d 18.64 parameter δ.sub.p 2.40 (MPa).sup.1/2 δ.sub.h 9.89 δ 21.21 Hansen solubility Unit (a) to base oil 5.98 parameter interaction Unit (b) to base oil 15.53 distance Copolymer to base oil 11.20 Lubricant Particle size <10 nm 0 composition distribution ≥10 nm, <50 nm 0 (%) ≥50 nm, <100 nm 0 ≥100 nm, <150 nm 0 ≥150 nm, <200 nm 0 ≥200 nm, <250 nm 0 ≥250 nm, <300 nm 22.4 ≥300 nm, <400 nm 30.7 ≥400 nm, <500 nm 24.2 ≥500 nm, <600 nm 12 ≥600 nm, <700 nm 5.9 ≥700 nm, <1000 nm 2.9 ≥1 μm, <5 μm 1.9 ≥5 μm, <10 μm 0 ≥10 μm 0

(19) The organic fine particle-dispersed solutions of Production Examples 3 to 12, like the organic fine particle-dispersed solution of Production Example 1, contained organic fine particles at a quantity of 0.01 to 50 parts by mass relative to 100 parts by mass of the base oil, and could be used as lubricant compositions that exhibit high lubrication performance. In addition, additives such as molybdenum dithiocarbamates may be added and used according to need.