Lubricating oil composition for internal combustion engine and method for producing same

Abstract

A lubricating oil composition for an internal combustion engine, which contains a lubricating oil base oil having a kinematic viscosity at 40 DEG C of 18.0 mm2 / s or less, and which does not contain an olefin copolymer. And an estimated value (X) of the amount of change per unit time in the amount of evaporation loss of the lubricating oil composition measured by a NOACK evaporability test under conditions of 150 DEG C and 12 hours as determined by a specific calculation formula is 0.45 mass% / hour or less.

Description

Technical Field

[0001] This invention relates to a lubricating oil composition for internal combustion engines and a method for manufacturing the same. Background Technology

[0002] Various compositions of lubricating oils for internal combustion engines have been studied to achieve effects such as low viscosity. For example, lubricating oil compositions for internal combustion engines have been disclosed that set the NOACK evaporation loss (measured at 250°C for 1 hour) within a specific range and the content of fractions with boiling points within a specific range within a specific range (e.g., Japanese Patent Application Publication No. 2021-024978 (Patent Document 1), Japanese Patent Application Publication No. 2021-025025, etc. (Patent Document 2)). However, conventional lubricating oil compositions for internal combustion engines are not necessarily sufficient in simultaneously achieving high levels of both low viscosity (an indicator of kinematic viscosity in the low-temperature region, including the room temperature region) and low volatility. Therefore, in the field of lubricating oil compositions for internal combustion engines, there is a need for new design concepts for lubricating oil compositions that can simultaneously achieve high levels of both low viscosity and low volatility in the low-temperature region—two seemingly incompatible properties.

[0003] Furthermore, the paper "Research on Ultra-High Viscosity Index Engine Oil: Part 1 - “Flat Viscosity” Concept and Contribution to Carbon Neutrality" (Non-Patent Document 1), published in the SAE International Journal of Advances and Current Practices in Mobility (vol.4, Issue 4) in 2022 (pages 1242-1249), discloses that the change in evaporation loss per unit time of the lubricating oil composition measured by the NOACK evaporation test under conditions of 150°C and 12 hours has a good relationship with the actual oil consumption in the engine.

[0004] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2021-024978 Patent Document 2: Japanese Patent Application Publication No. 2021-025025 Non-patent literature Non-patent document 1: "Research on Ultra-High Viscosity Index Engine Oil: Part1-"Flat Viscosity" Concept and Contribution to Carbon Neutrality", SAEInternational Journal of Advances and Current Practices in Mobility, released in 2022, vol.4, Issue 4, P.1242-P.1249 Summary of the Invention

[0005] The problem that the invention aims to solve The present invention was made in view of the problems of the prior art, and its object is to provide a lubricating oil composition for internal combustion engines that can simultaneously achieve a high level of low kinematic viscosity and low volatility in the low temperature region; and to provide a method for manufacturing a lubricating oil composition for internal combustion engines that can easily determine the design of the composition to achieve low volatility using a specific formula, and can efficiently manufacture a lubricating oil composition for internal combustion engines that simultaneously achieves a high level of low kinematic viscosity and low volatility in the low temperature region.

[0006] Methods for solving problems In order to achieve the aforementioned objective, the inventors first designed the composition of the lubricating oil used in internal combustion engines to achieve a desired level of both low viscosity in the low-temperature region, including the room temperature region, and evaporability, a performance that is mutually exclusive when achieving low viscosity. Starting from the perspective of examining whether the evaporability of the composition can be effectively predicted in advance based on physicochemical principles, they conducted repeated and in-depth research, deriving the following equation (1). This indicates that the phenomenon of oil consumption is a kinetic phenomenon and cannot be simply associated with the energy theory of distillation after measuring a stable state over a sufficient period of time. By establishing reasonable variables based on research utilizing natural laws, and compared to examples in the known literature where boiling point ranges are discontinuously divided to correlate evaporation characteristics without reasonable calculations, reasonable numerical calculations and technical applications can be performed based on knowledge related to general physicochemical principles. That is, considering the facts described in Non-Patent Document 1, the inventors have repeatedly conducted in-depth research in order to efficiently design a composition that achieves both evaporability and low viscosity—performances that are mutually exclusive when achieving low viscosity—and found that, firstly, by deriving the following formula (1) and using the calculated value X obtained from formula (1), the evaporation characteristics of the composition can be effectively predicted. Furthermore, with this understanding, the inventors have further conducted repeated research to achieve the aforementioned objective and found that by making the internal combustion engine lubricating oil composition have the following composition: the kinematic viscosity of the lubricating oil base oil in the composition at 40°C is 18.0 mm. 2 The lubricating oil composition does not contain olefin copolymers and the estimated value X obtained by the following formula (1) is less than 0.45% by mass per hour, thereby enabling the composition to simultaneously achieve a high level of low kinematic viscosity and low evaporability in the low temperature region, thus completing the present invention.

[0007] That is, the present invention provides the following solution.

[0008] [1] A lubricating oil composition for internal combustion engines, comprising a lubricating oil base oil, wherein... The kinematic viscosity of the lubricating oil base oil at 40°C is 18.0 mm. 2 / s or less The lubricating oil composition does not contain olefin copolymers, and The estimated value X, obtained by formula (1) below, is less than 0.45 wt% / hour, representing the change in evaporation loss per unit time of the lubricating oil composition determined by the NOACK evaporation test at 150°C for 12 hours. [In the formula, Y represents the estimated total evaporation loss of the lubricating oil composition determined by the NOACK evaporation test under conditions of 150°C and 12 hours, obtained by formula (2) below.] (In equation (2), i represents an integer in the range of 25 to 75, A(i) represents the percentage of components (in mass%) in the total amount of the lubricating oil composition, based on the boiling point of the components determined by gas chromatography distillation within the range of {(i-1)×10}℃ and below (i×10)℃. B(i) represents the value obtained by equation (3) below (where B(i) is considered to be 100 if the calculated value of B(i) exceeds 100). .

[0009] [2] The internal combustion engine lubricating oil composition according to [1], wherein the calculated value X is less than 0.35% by mass / hour.

[0010] [3] The internal combustion engine lubricating oil composition according to [1] or [2], wherein the kinematic viscosity of the lubricating oil base oil at 100°C is 2.7 mm. 2 / s or higher and 4.1mm 2 / s or less.

[0011] [4] The lubricating oil composition for internal combustion engines according to any one of [1] to [3], wherein the lubricating oil base oil comprises at least one mineral oil base oil as a base oil component constituting the lubricating oil base oil.

[0012] [5] The internal combustion engine lubricating oil composition according to any one of [1] to [4] further contains a viscosity index improver, and the viscosity index improver is poly(meth)acrylate.

[0013] [6] A method for manufacturing a lubricating oil composition for internal combustion engines containing a lubricating oil base oil, wherein, Lubricating oil compositions for internal combustion engines are manufactured by designing their composition in the following manner: The kinematic viscosity of the lubricating oil base oil at 40°C is set to 18.0 mm. 2 / s or less The lubricating oil composition is free of olefin copolymers, and The estimated value X of the change in evaporation loss per unit time of the lubricating oil composition determined by the NOACK evaporation test at 150°C and 12 hours, obtained by formula (1), is less than 0.45% by mass / hour.

[0014] Invention Effects According to the present invention, a lubricating oil composition for internal combustion engines can be provided, which simultaneously achieves a high level of low kinematic viscosity and low volatility in the low-temperature region; and a method for manufacturing a lubricating oil composition for internal combustion engines can be provided, which can easily determine the design of the composition to achieve low volatility using a specific formula, and can efficiently manufacture a lubricating oil composition for internal combustion engines that simultaneously achieves a high level of low kinematic viscosity and low volatility in the low-temperature region. Attached Figure Description

[0015] Figure 1 A graph showing the relationship between the boiling point and evaporation loss of components in 15 samples of lubricating oil compositions.

[0016] Figure 2 It is a graph showing the relationship between the estimated value of the change in NOACK evaporation loss per unit time of the lubricating oil composition and the measured value (actual value) of the change in NOACK evaporation loss per unit time (slope). Detailed Implementation

[0017] Hereinafter, the present invention will be described in detail according to preferred embodiments. It should be noted that, unless otherwise specified, in this specification, the expression "X~Y" for numerical values ​​X and Y means "X or more and Y or less". When a unit is applied only to the numerical value Y in this expression, that unit also applies to the numerical value X.

[0018] [Lubricating Oil Composition for Internal Combustion Engines] The lubricating oil composition for internal combustion engines of the present invention is a lubricating oil composition for internal combustion engines containing a lubricating oil base oil, wherein, The kinematic viscosity of the lubricating oil base oil at 40°C is 18.0 mm. 2 / s or less The lubricating oil composition does not contain olefin copolymers, and The estimated value X of the change in evaporation loss per unit time of the lubricating oil composition determined by the NOACK evaporation test at 150°C for 12 hours, obtained by formula (1), is less than 0.45% by mass / hour.

[0019] It should be noted that, for convenience, in this specification, the NOACK evaporation test according to ASTM D5800, and tests conducted under the same conditions as the NOACK evaporation test according to ASTM D5800, except for changes in the test procedure (changing the test temperature and / or conducting the test multiple times without replenishing and extracting samples after a single test), are all referred to as the "NOACK evaporation test". Furthermore, for convenience, in this specification, the evaporation amount (evaporation loss) obtained by the NOACK evaporation test according to ASTM D5800, and the evaporation amount (evaporation loss) obtained by tests conducted under the same conditions as the NOACK evaporation test, except for changes in the test procedure (changing the test temperature and / or conducting the test multiple times without replenishing and extracting samples after a single test), are all referred to as the "NOACK evaporation loss" (because these evaporation amounts are values ​​obtained based on the NOACK evaporation test).

[0020] Furthermore, in this specification, all base oils contained as components of a lubricating oil base oil are referred to as "base oil components." Additionally, compositions of base oils formed from all the base oil components contained as components (wherein, "composition" includes cases formed from only one base oil component) are referred to as "lubricating oil base oil." Thus, in this specification, when a lubricating oil composition contains only one base oil component, the base oil composed solely of that one base oil component (all base oils in the lubricating oil composition) is referred to as "lubricating oil base oil." Furthermore, when the lubricating oil composition contains multiple base oil components, the mixture of base oils composed of those multiple base oil components (all base oils in the lubricating oil composition) is referred to as "lubricating oil base oil," and each base oil contained as a component of that lubricating oil base oil is referred to as a "base oil component."

[0021] Here, firstly, the estimated value X of the change in the amount of evaporation loss of the lubricating oil composition per unit time as determined by the NOACK evaporation test under the conditions of 150°C and 12 hours (in other words, the estimated value X of the change in the amount of NOACK evaporation loss of the lubricating oil composition per unit time when measured under the conditions of 150°C and 12 hours) obtained by the above formula (1) will be explained together with the method of deriving the above formula (1).

[0022] The calculated value X is obtained by the following formula (1).

[0023] In addition, Y in such formula (1) represents the estimated value of the total amount of evaporation loss of the lubricating oil composition determined by the NOACK evaporation test under the conditions of 150°C and 12 hours, obtained by formula (2) below (in other words, the estimated value of the total amount of NOACK evaporation loss of the lubricating oil composition under the conditions of 150°C and 12 hours: hereafter, this estimated value is sometimes simply referred to as "estimated value Y").

[0024] (In equation (2), i represents an integer in the range of 25 to 75, A(i) represents the percentage of components (in mass%) in the total amount of the lubricating oil composition, based on the boiling point of the components determined by gas chromatography distillation within the range of {(i-1)×10}℃ and below (i×10)℃. B(i) is the value obtained by formula (3) for each value of i (where B(i) is considered to be 100 if the calculated value of B(i) exceeds 100). .

[0025] Equation (2) used to derive such a calculated value Y is established by studying the evaporation characteristics using a large number (15 kinds) of samples that are generalized in a way that can be applied to all kinds of compositions (derived by generalizing the evaporation characteristics of the compositions of each sample).

[0026] Here, Equation (3) used to derive B(i) in Equation (2) will be explained. First, in the field of lubricating oil compositions for internal combustion engines, it is generally known that the change in evaporation loss per unit time (the change in evaporation loss of NOACK (150°C, 12 hours)) measured based on the NOACK evaporation test (hereinafter, sometimes abbreviated as "NOACK (150°C, 12 hours)") conducted under ASTM D5800 at 150°C for 12 hours shows an extremely good correlation with the actual oil consumption of the engine (see, for example, Non-Patent Literature 1). Starting from these well-known facts, the inventors further conducted research, preparing samples of 15 lubricating oil compositions. For each sample, based on the test method specified in ASTM D5800, three NOACK evaporation tests were performed at 150°C for 4 hours. (It should be noted that the test was temporarily stopped after every 4 hours, and the cooling procedure specified in the test method was performed before the test was repeated. A total of three NOACK evaporation tests at 150°C for 4 hours were conducted in this manner. These three tests used 150°C for 12 hours; otherwise, they were considered to be in accordance with ASTM standards.) The NOACK evaporation test specified in D5800 is essentially the same test. Therefore, for convenience, this test will sometimes be abbreviated as "NOACK (150°C, 12 hours)" below. The evaporation characteristics of the components in the lubricating oil composition before and after the NOACK (150°C, 12 hours) test will be compared. The results showed that in this test, no loss of components with boiling points below a specific temperature or no loss of components with boiling points above a specific temperature was observed in any of the samples. Even under the test conditions of 150°C, the composition actually contained multiple components with boiling points in the range of {(i-1)×10}°C above and below (i×10)°C (where i is any integer value in the range of 25 to 75 when representing components). Further explanation is needed. It should be noted that the various components mentioned here include those whose boiling point temperature is higher than the test temperature (150°C) based on the value of i. ) Despite the limitations caused by the detection limit, the amount of loss will vary continuously. In more detail, firstly, samples of 15 lubricating oil compositions (including samples of lubricating oil compositions with compositions used in Examples 1 to 3 described later in this application) were prepared, and each sample was subjected to a NOACK evaporation test at 150°C for 4 hours three times as described above, thereby conducting a NOACK (150°C, 12 hours) test. Then, for each sample before and after the test, a gas chromatographic distillation test was conducted under the following conditions (A) (it should be noted that, for convenience, the gas chromatographic distillation test under condition (A) will sometimes be referred to as "gas chromatographic distillation test (A)").It should be noted that the gas chromatographic distillation test (A) is a test with appropriate changes to conditions, etc., in order to obtain the target data, based on the test method described in JIS K2254.

[0027] [Conditions for gas chromatographic distillation test (A)] Measuring device: Shimadzu Corporation, Product name: GC-2030 Column: Superalloy-1HT (UA-1HT; length 5m, inner diameter (ID) 0.5mm, film thickness 0.1μm: manufactured by Frontier Laboratories) Carrier gas: He (flow rate: 15 mL / min) Detector: Flame Ionization Detector (FID) Detector temperature: 400℃ Inlet temperature: Programmed temperature vaporization (PTV) injection port, 40℃~380℃ Column temperature: After holding at 40℃ for 6 minutes, increase the temperature to 380℃ at a rate of 10℃ / minute.

[0028] Then, based on the results of the gas chromatographic distillation test (A) performed on each sample before and after the NOACK evaporation test (NOACK (150°C, 12 hours) test) conducted as described above at 150°C for 4 hours, for the fractions at temperatures above {(i-1)×10}°C and below (i×10)°C (where i is an integer from 25 to 75), the difference in content before and after the test is calculated for each fraction (based on each value of i) taking into account the evaporation loss. For components with boiling points in the range of above {(i-1)×10}°C and below (i×10)°C (where i is an integer from 25 to 75), the difference calculated for each value of i is the evaporation loss obtained from the NOACK (150°C, 12 hours) test for each component at each boiling point. Therefore, for each sample, the evaporation loss of each component (i being an integer from 25 to 75) with a boiling point above {(i-1)×10}℃ and below (i×10)℃ was calculated, and all these loss values ​​were plotted in the same graph. However, in such determinations, to eliminate the influence of experimental errors caused by limitations in experimental precision that are excessively reflected in the results, the measurement data of components with a content of less than 1% by mass before the test (components with a boiling point above {(i-1)×10}℃ and below (i×10)℃) and the measurement data where the change in the composition before and after the test is less than 0% are excluded. The graph showing the relationship between the boiling point and evaporation loss of the components with i between 31 and 50 mainly contained in the 15 samples obtained in this way is shown in the figure. Figure 1Furthermore, an approximate curve is derived from the graph obtained based on the values ​​of such evaporation losses, and this approximate curve is also presented here. Figure 1 .

[0029] Depend on Figure 1 As shown in the charts, the actual boiling points of the various components (where i represents any integer value in the range of 25 to 75 for each component) contained in the compositions of each sample vary continuously in amount, regardless of their boiling point temperature, despite the limitations imposed by the detection limit. On the other hand, based on such... Figure 1 The results show that the proportion of evaporation loss (evaporation amount) varies depending on the boiling point range of each component (for each value of i). Therefore, regarding the reason for the difference in the proportion of evaporation loss (evaporation amount), the inventors investigated whether the phenomenon of oil consumption is a kinetic phenomenon, for example, whether it differs from phenomena that can be analyzed using energy theory, such as a steady state achieved solely through distillation over a sufficient period of time. Furthermore, based on this understanding, in order to establish a reasonable variable relative to the amount of evaporation loss, the inventors determined... Figure 1 The approximate curve described therein is used as an approximation to derive the formula represented by Equation (3). Moreover, based on such an approximation, the evaporation loss of each component can be estimated (calculated) according to the range of boiling points of each component (based on each value of i) based on the content of each component (i is an integer from 25 to 75) with a boiling point in the range of {(i-1)×10}℃ and below (i×10)℃, and the estimated loss ratio of that component obtained by the approximation (Equation (3)). In this way, it can be seen from the approximation that, with reasonable variables, it is easy to study the composition that takes into account both low viscosity characteristics and low evaporability. It should be noted that in known patent publications, etc., it is common to see cases where evaporation characteristics are defined only by the boiling point range, but the inventors speculate that, compared with such prior art, a more accurate examination can be performed by using the approximation described above.

[0030] Thus, in this invention, samples of 15 lubricating oil compositions (sufficient quantity of samples for deriving the general formula used to calculate the estimated value) are subjected to a NOACK (150°C, 12 hours) test as described above (three tests at 150°C, 4 hours each). Using samples before and after the test, the evaporation loss (proportion) of various components (i being any integer value in the range of 25 to 75 representing the component) in compositions with boiling points above {(i-1)×10}°C and below (i×10)°C is calculated, and the formula (3) is derived based on this value. Since it is derived from this operation, it can be said that the formula (3) is a formula for deriving the estimated value (estimated value) of the loss proportion of each component (i being an integer in the range of 25 to 75) with boiling points above {(i-1)×10}°C and below (i×10)°C in the NOACK (150°C, 12 hours) test. It should be noted that since B(i) is calculated as an estimated value (coefficient) of the proportion of evaporation loss of each component, when the calculated value of B(i) exceeds 100, B(i) is treated as 100 and used in equation (2).

[0031] Next, A(i) in equation (2) will be explained. A(i) represents the percentage (in mass%) of components whose boiling point, determined by gas chromatographic distillation, falls within the range of {(i-1)×10}℃ to (i×10)℃, based on the total amount of the lubricating oil composition (where i represents an integer in the range of 25 to 75). As such a gas chromatographic distillation-based determination method, the same method as described in the above-mentioned "Gas Chromatographic Distillation Test (A)" is used. Regarding the value of A(i), considering the experimental precision (experimental error) in the gas chromatographic distillation test (A), components with a measured percentage (value of A(i)) less than 0.01% by mass are considered to have a value of 0 for use in the calculation of equation (2).

[0032] It should be noted that in the above formula (2), i is an integer in the range of 25 to 75. The sum of the calculated values ​​of A(i) × B(i) within the range of i is obtained. For example, if it is known that the composition does not contain any component with a boiling point of 600°C or higher, A(i) is obtained in the range of 25 to 60 for i. For components with i in the range of 61 to 70, A(i) can be treated as 0 for calculation (because, for components with a boiling point of 600°C or higher, if it is known that A(i) is 0 even if measured, there is no point in specifically calculating A(i), and it has no effect on the calculated value). That is, as mentioned above, if it is known that the composition does not contain any component with a boiling point of 600°C or higher, formula (2) can also be calculated as the following formula (2') (because, in the part where i is 61 or higher, the calculated value of "A(i) × B(i)" is always 0). In this way, when it is clear that the composition does not contain a component whose value of i is a specific value or higher than the boiling point index of that component (in the case that the above example does not contain a component whose value of i is 61 or higher), the upper limit of the calculated value range of i (the value range of i obtained by summing) can be appropriately changed, and the calculation can be performed within a practical range. From this point of view, considering the types of components that can usually be used, when the practical value range of i is 25 to 60, it is preferable to change the value range of i to 25 to 60 for calculation (it should be noted that in this case, in the part where i is 61 or higher, the calculated value of "A(i) × B(i)" is always 0, so it has the same meaning as calculating formula (2) which includes the range of i from 61 to 75).

[0033] (In equation (2'), A(i) and B(i) have the same meaning as those in equation (2), except that i is an integer in the range of 25 to 60.) Furthermore, in this invention, in equation (2), the calculated value of "A(i)×B(i)" is obtained for each value of i, and the sum of these values ​​is used to calculate the estimated total NOACK evaporation loss of the lubricating oil composition under the assumed conditions of 150°C and 12 hours. It should be noted that B(i) is a coefficient relating to the proportion of loss due to evaporation for each component under the assumed conditions of 150°C and 12 hours when the NOACK evaporation test is conducted. Therefore, the calculated value of "A(i)×B(i)" becomes the estimated value of the evaporation amount of each component under the assumed conditions of 150°C and 12 hours when the NOACK evaporation test is conducted, and the sum of these values ​​becomes the estimated total NOACK evaporation loss of the lubricating oil composition under the assumed conditions of 150°C and 12 hours when the NOACK evaporation test is conducted.

[0034] Next, the calculated value X obtained by using the calculated value Y obtained through equation (2) will be explained. Here, equation (1) is as follows.

[0035] Equation (1) is derived as follows. First, using the results of the NOACK (150°C, 12 hours) test on the 15 samples used to derive Equation (3), the difference in the total amount of the lubricating oil composition before and after the test is calculated for each sample, and the measured value (actual value) of the change in NOACK evaporation loss per unit time (mass% / hour) is obtained. Next, the estimated value Y is calculated for each sample, and for all samples, the relationship between the change in NOACK evaporation loss per unit time (slope) and the estimated value Y is plotted to obtain a graph. Then, based on this graph, an approximate formula representing the relationship between the estimated value Y and the change in NOACK evaporation loss per unit time is obtained, thereby deriving Equation (1).

[0036] It should be noted that, in order to confirm the validity of such equation (1), for 62 samples containing the compositions used in the examples and comparative examples described below, the estimated value X and the measured value (actual value) of the change (slope) of NOACK evaporation loss per unit time were calculated respectively, and their relationship is shown in... Figure 2 From this perspective Figure 2 The results show that the correlation coefficient between the estimated value X and the measured value is 0.94. It should be noted that if the inherent experimental errors of the testing machine are considered in the NOACK evaporation test or the gas chromatographic distillation test, the correlation coefficient cannot be strictly 1. Therefore, the estimated value X obtained from equation (1) is a very accurate approximation of the change in NOACK evaporation loss per unit time. Thus, the estimated value X becomes an approximation of the change in NOACK evaporation loss per unit time obtained from the estimated value Y. Therefore, according to the present invention, by using the estimated value X to consider evaporation, the evaporation characteristics of the lubricating oil composition can be studied (estimated) with high accuracy.

[0037] In this invention, the calculated value X obtained by equation (1) needs to be 0.45 wt% / hour or less. By setting this calculated value X to 0.45 wt% / hour or less, the evaporation loss of the composition during actual use can be reduced, making the composition excellent in terms of low evaporation. Furthermore, from the viewpoint that even greater effects can be obtained, the value of the calculated value X is preferably 0.40 wt% / hour or less, more preferably 0.35 wt% / hour or less, and even more preferably 0.30 wt% / hour or less.

[0038] Furthermore, the lubricating oil composition for internal combustion engines of the present invention contains a lubricating oil base oil as an essential component. Moreover, the kinematic viscosity of this lubricating oil base oil (all base oils) at 40°C needs to be 18.0 mm. 2 / s or less. Thus, the lubricating oil composition for internal combustion engines of the present invention has a kinematic viscosity of 18.0 mm at 40°C. 2 Lubricating oil base oils with a viscosity of less than 600 kJ / s (all base oils) are required components. The kinematic viscosity of such lubricating oil base oils at 40°C is set to 18.0 mm. 2 A viscosity of 9.8 m / s or less can achieve a low kinematic viscosity in the low-temperature region of the final composition. From the perspective that a higher effect can be obtained from the same point of view, a kinematic viscosity of 9.8 m / s at 40°C for such a lubricating oil base oil is more preferably 9.8 m / s. 2 / s or higher and 16.6mm 2 / s or less, and more preferably 9.8mm 2 / s or higher and 15.8mm 2 / s or less, with 12.5mm being particularly preferred. 2 / s or higher and 14.9mm 2 For speeds below 1 / s, the optimal value is 12.5mm. 2 / s or higher and 12.8mm 2 / s or less. It should be noted that by setting the kinematic viscosity of the lubricating oil base oil at 40°C to above the aforementioned lower limit, an oil film can be formed more efficiently in low-temperature lubrication areas.

[0039] Furthermore, the kinematic viscosity of the lubricating oil base oil (all base oils) at 100°C is preferably 2.7 mm. 2 / s or higher and 4.1mm 2 / s or less, preferably 2.9mm 2 / s or higher and 3.7mm 2 / s or less. This is achieved by setting the kinematic viscosity of the lubricating oil base oil at 100°C to 4.1 mm. 2 Excellent fuel-saving performance can be achieved by maintaining a kinematic viscosity of less than 2.7 mm³ / s. Furthermore, the kinematic viscosity of the lubricating oil base oil at 100°C is reduced to 2.7 mm³ / s. 2 A speed of 1000 m / s or higher ensures the formation of an oil film at the lubrication points and further reduces the evaporation loss of the lubricating oil composition.

[0040] It should be noted that in this specification, "kinematic viscosity at 40°C" and "kinematic viscosity at 100°C" refer to values ​​measured according to ASTM D-445. It should also be noted that, hereinafter, the "kinematic viscosity at 40°C" of the base oil or composition may sometimes be abbreviated as "40°C kinematic viscosity," and the "kinematic viscosity at 100°C" of the base oil or composition may sometimes be abbreviated as "100°C kinematic viscosity."

[0041] Furthermore, in such lubricating oil base oils (all base oils), the content of components with a boiling point below 330°C is preferably 2.0% by mass or less (more preferably 1.7% by mass or less). By setting the content of such components with a boiling point below 330°C to below the aforementioned upper limit, evaporation losses during use can be further reduced, and a higher effect can be obtained in terms of low volatility. It should be noted that the content of the aforementioned components in the lubricating oil base oil can be determined as follows: the lubricating oil base oil is subjected to the aforementioned gas chromatographic distillation test (A), and the proportion of components with a boiling point below 330°C relative to the total amount of the lubricating oil base oil is calculated from the obtained gas chromatogram.

[0042] Furthermore, the evaporation loss (NOACK (250°C, 1 hour) evaporation loss) of such lubricating oil base oils (all base oils) determined according to ASTM D5800 at 250°C for 1 hour (hereinafter, sometimes abbreviated as "NOACK (250°C, 1 hour)") is preferably 16.0 to 31.0% by mass (more preferably 18.0 to 29.8% by mass, and even more preferably 20.4 to 24.8% by mass). By setting the NOACK (250°C, 1 hour) evaporation loss below the upper limit, there is a tendency to obtain a higher effect in terms of low volatility; on the other hand, by setting it above the lower limit, there is a tendency to obtain a higher effect in terms of improving fuel-saving performance based on the low viscosity of the lubricating oil composition.

[0043] As described above, such lubricating oil base oils (all base oils) can be composed of a single base oil component, or they can be composed of a mixture of multiple (two or more) base oil components. As the constituent components of such lubricating oil base oils (all base oils), i.e., the base oil components, either mineral oil-based base oils or synthetic base oils can be used.

[0044] There are no particular limitations on the mineral oil-based base oils that can be used as components of the base oil; distillate oils obtained by atmospheric distillation of crude oil can be used. Alternatively, lubricating oil fractions obtained by further vacuum distillation of the distillate oil can be used, refined through various refining processes. Refining processes can include appropriate combinations of hydrorefining, solvent extraction, solvent dewaxing, hydrodewaxing, sulfuric acid washing, and clay treatment. By combining these refining processes in an appropriate sequence, a lubricating oil base oil suitable for use in the lubricating oil compositions of the present invention can be obtained. A mixture of various refined oils with different properties, obtained by combining different crude oils or distillate oils with different refining processes, can also be used.

[0045] Furthermore, as a mineral oil-based base oil that can be used as a component of the base oil, a mineral oil-based base oil belonging to Group III of the API classification is preferred. API Group III base oils are mineral oil-based base oils with a sulfur content of 0.03% by mass or less, a saturation content of 90% by mass or more, and a viscosity index of 120 or more. When using API Group III base oils, multiple Group III base oils can be used, or only one Group III base oil can be used. Alternatively, as a mineral oil-based base oil that can be used as a component of the base oil, a mineral oil-based base oil belonging to Group II of the API classification can also be used. API Group II base oils are mineral oil-based base oils with a sulfur content of 0.03% by mass or less, a saturation content of 90% by mass or more, and a viscosity index of 80 or more and less than 120. When using API Group II base oils, multiple Group II base oils can be used, or only one Group II base oil can be used.

[0046] In addition, synthetic base oils that can be used as components of the aforementioned base oils include polyalphaolefins and their hydrogenated derivatives, isobutylene oligomers and their hydrogenated derivatives, isoparaffins, alkylbenzenes, alkylnaphthalenes, diesters, polyol esters, polyoxyalkylene glycols, dialkyl diphenyl ethers, polyphenylene ethers, and mixtures thereof. Among these, polyalphaolefins are preferred. Typical examples of polyalphaolefins include oligomers or co-oligomers (1-octene oligomers, decene oligomers, ethylene-propylene co-oligomers, etc.) of alpha-olefins having 2 to 32 carbon atoms, preferably 6 to 16 carbon atoms, and their hydrogenated derivatives.

[0047] Furthermore, as the base oil of the lubricating oil (all base oils), it is preferable that the base oil components constituting the lubricating oil base oil include at least one mineral oil-based base oil. That is, as such a lubricating oil base oil, it is preferable that it is not composed of only synthetic base oils (of which, it is particularly preferable that it is not composed of only Fischer-Tropsch base oils). By making the lubricating oil base oil not only composed of synthetic base oils (containing at least one mineral oil-based base oil), fuel-saving performance can be improved by modifying the viscosity-temperature characteristics of the composition, while further reducing the evaporation loss of the lubricating oil composition. In addition, from the viewpoint of obtaining even greater effects, as the lubricating oil base oil, it is preferable that it does not contain (utilize) synthetic base oils (such as Fischer-Tropsch base oils, etc.) as components of the lubricating oil base oil, i.e., base oil components.

[0048] Furthermore, when the lubricating oil base oil (all base oils) contains at least one mineral oil-based base oil in its base oil composition, the content of the mineral oil-based base oil, based on the total amount of the lubricating oil base oil, is preferably 87% by mass or more and 100% by mass or less, more preferably 95% by mass or more and 100% by mass or less. By setting the content of the mineral oil-based base oil in the lubricating oil base oil to the lower limit or above, the fuel-saving performance can be improved by modifying the viscosity-temperature characteristics of the composition, while further reducing the evaporation loss of the lubricating oil composition.

[0049] Furthermore, in the lubricating oil composition for internal combustion engines of the present invention, the content of the lubricating oil base oil (all base oils) is preferably 70.0% by mass or more and 95.0% by mass or less, more preferably 75.3% by mass or more and 90.0% by mass or less, and particularly preferably 85.6% by mass or more and 89.9% by mass or less, based on the total amount of the lubricating oil composition for internal combustion engines. Setting the content of the lubricating oil base oil at or above the lower limit results in a higher effect on the solubility stability of the additives compared to a content below the lower limit. On the other hand, setting the content of the lubricating oil base oil at or below the upper limit allows for the application of additives, making it easier to meet the intended use in terms of viscosity-temperature characteristics, detergency stability, and other properties.

[0050] Furthermore, the lubricating oil composition for internal combustion engines of the present invention must be free of olefin copolymers. If the lubricating oil composition for internal combustion engines contains olefin copolymers, it is impossible to reduce the kinematic viscosity in the low-temperature region, thus reducing fuel efficiency.

[0051] Furthermore, the lubricating oil composition for internal combustion engines of the present invention may appropriately contain additives that can be used together with the lubricating oil base oil in the lubricating oil composition for internal combustion engines. As such additives, known additives for internal combustion engine lubricating oil compositions can be appropriately utilized without particular limitation. Preferably, viscosity index improvers, metal detergents, molybdenum-based friction modifiers, ashless friction modifiers, antioxidants, anti-wear agents, dispersants, pour point depressants, demulsifiers, metal passivators, and defoamers are preferred. More preferably, viscosity index improvers, metal detergents, molybdenum-based friction modifiers, ashless friction modifiers, antioxidants, anti-wear agents, and dispersants are preferred (it should be noted that the additives listed here are suitable examples, and the available additives are not limited to these). Such additives can be used alone or in combination of two or more.

[0052] Furthermore, the lubricating oil composition for internal combustion engines of the present invention preferably further comprises a viscosity index improver. Here, "viscosity index improver" refers to a compound that, when added to a lubricating oil, has the function of reducing the viscosity change of the lubricating oil that occurs with temperature variations. As such a viscosity index improver, any viscosity index improver used in the field of lubricating oil compositions (excluding olefin copolymers) can be appropriately used, provided that the effects of the present invention are achieved. Examples include polybutene (PB), polyisobutylene (PIB), ethylene-propylene copolymer (EPC), poly(meth)acrylate (PMA), and styrene-diene copolymer (SDC). It should be noted that in this specification, "(meth)acrylate" refers to acrylates and / or methacrylates, and "poly(meth)acrylate" refers to a polymer containing acrylate monomer units and / or methacrylate monomer units.

[0053] Furthermore, when the internal combustion engine lubricating oil composition of the present invention contains a viscosity index improver, from the viewpoint that by improving the viscosity-temperature characteristics, while maintaining a low viscosity in the low-temperature region and increasing the viscosity in the high-temperature region, the fuel-saving performance can be further improved, the viscosity index improver is more preferably poly(meth)acrylate (more preferably polymethacrylate). Additionally, as such a poly(meth)acrylate (PMA), any one of dispersed poly(meth)acrylate, non-dispersed poly(meth)acrylate, and comb-type poly(meth)acrylate can be used, without particular limitation. From the viewpoint that by improving the viscosity-temperature characteristics, while maintaining a low viscosity in the low-temperature region and increasing the viscosity in the high-temperature region, thereby further enhancing the effect of improving fuel-saving performance, comb-type poly(meth)acrylate is preferred.

[0054] Here, "dispersed poly(meth)acrylate" refers to a poly(meth)acrylate compound having a functional group containing a nitrogen atom, and "non-dispersed poly(meth)acrylate" refers to a poly(meth)acrylate compound not having a functional group containing a nitrogen atom. Furthermore, as the comb-type poly(meth)acrylate, known poly(meth)acrylate polymers having a so-called comb structure can be appropriately utilized (e.g., "comb polymer" described in Japanese Patent Application Publication No. 2017-101211, "comb poly(meth)acrylate" described in Japanese Patent Application Publication No. 2018-177986, "comb poly(meth)acrylate" described in International Publication No. 2016 / 159006, "viscosity index improver" described in Japanese Patent Application Publication No. 2017-110196, "(co)polymer (A)" described in Japanese Patent Application Publication No. 2017-110196, etc.). It should be noted that, for example, such comb-type poly(meth)acrylates can be derived from macromonomers derived from the hydrides of polyolefins obtained by copolymerizing butadiene and isoprene.

[0055] Furthermore, the weight-average molecular weight (Mw) of the viscosity index improver is, for example, 10,000 or more and 1,000,000 or less, preferably 50,000 or more and 900,000 or less, more preferably 100,000 or more and 800,000 or less, and even more preferably 150,000 or more and 600,000 or less. It should be noted that the Mw / Mn (weight-average molecular weight / number-average molecular weight) of the viscosity index improver is, for example, 2.3 or more and 6.0 or less, preferably 2.5 or more and 5.5 or less, more preferably 3.0 or more and 5.0 or less. By keeping the Mw / Mn within the above range, the viscosity index can be well maintained. It should be noted that in this specification, the weight-average molecular weight Mw and number-average molecular weight Mn of the viscosity index improver refer to values ​​obtained by gel permeation chromatography (GPC) (molecular weight converted from polystyrene).

[0056] When the internal combustion engine lubricating oil composition of the present invention contains a viscosity index improver, the content of the viscosity index improver, calculated as resin component, is preferably 0.1% by mass or more and 20% by mass or less based on the total composition, more preferably 1.0% by mass or more and 10% by mass or less, and even more preferably 1.5% by mass or more and 3.0% by mass or less. By setting the content of such a viscosity index improver, calculated as resin component, to the upper limit or below, viscosity-temperature characteristics can be improved while maintaining detergency. On the other hand, by setting the content of such a viscosity index improver, calculated as resin component, to the lower limit or above, viscosity-temperature characteristics can be improved by achieving a lower viscosity in the low-temperature region, including the room temperature region, while adjusting the kinematic viscosity at high temperatures to be the same. It should be noted that the "content of the viscosity index improver, calculated as resin component" mentioned here refers to the content of the resin component constituting the viscosity index improver in the lubricating oil composition. In this specification, "resin component" refers to a polymer component with a molecular weight of 1000 or more.

[0057] Furthermore, the lubricating oil composition for internal combustion engines of the present invention preferably contains a metallic detergent. Examples of such metallic detergents include calcium-based detergents, magnesium-based detergents, and / or barium-based detergents. These detergents can be highly alkalineized with boric acid, borates, carbonic acid, or carbonates. As metallic detergents, metallic detergents having a salicylic acid group (metallic detergents with a salicylic acid structure), metallic detergents having a sulfonic acid group, or metallic detergents having a phenolic group can be used. Metallic detergents having a salicylic acid group (metallic detergents with a salicylic acid structure) are preferred.

[0058] Furthermore, as such a metal-based detergent, a metal-based detergent containing magnesium carbonate is preferred. Examples of preferred metal-based detergents include those containing magnesium carbonate and salicylic acid groups, and those containing magnesium carbonate and sulfonic acid groups. Such metal-based detergents can be used alone or in combination of two or more (e.g., using a metal-based detergent containing magnesium carbonate with a metal-based detergent containing a metal other than magnesium).

[0059] When the internal combustion engine lubricating oil composition of the present invention contains a metal-based detergent, the specific range of the amount of metal derived from the metal-based detergent, based on the total amount of the composition, is preferably 100 ppm by mass or more and 2200 ppm by mass or less (more preferably 453 ppm by mass or more and 1901 ppm by mass or less, and even more preferably 1400 ppm by mass or more and 1901 ppm by mass or less). In this specification, unless otherwise specified, the content of each element in the oil—calcium, magnesium, sulfur, zinc, boron, phosphorus, and molybdenum—is determined according to JIS K0116 by inductively coupled plasma atomic emission spectrometry (intensity ratio method (internal standard method)). By setting the amount of metal derived from the metal-based detergent to the upper limit mentioned above, compared with cases exceeding the upper limit, the sulfuric acid ash content can be reduced, and consequently, the coefficient of friction can also be reduced.

[0060] The base value (perchloric acid method) range of the metal-based detergent used in the internal combustion engine lubricating oil composition of the present invention is preferably 10 mg KOH / g or more and 650 mg KOH / g or less, more preferably 190 mg KOH / g or more and 400 mg KOH / g or less. It should be noted that, in this specification, the base value (perchloric acid method) of the metal-based detergent is a value determined according to JIS K 2501:2003-9.

[0061] Furthermore, the lubricating oil composition for internal combustion engines of the present invention preferably includes a molybdenum-based friction modifier. There are no particular limitations on such a molybdenum-based friction modifier; known molybdenum-based friction modifiers can be appropriately used, and molybdenum dithiocarbamate (hereinafter, sometimes simply referred to as "MoDTC"), dialkylamine molybdate, etc., are preferred. Moreover, such a molybdenum-based friction modifier preferably includes MoDTC, and particularly preferably MoDTC. By using such a molybdenum-based friction modifier, the coefficient of friction can be reduced. Such a molybdenum-based friction modifier can be used alone, or two or more can be used in any proportion.

[0062] Alternatively, the MoDTC can be, for example, a compound represented by the following formula (A).

[0063] (A) In the formula (A), R 1 ~R 4The alkyl groups can be the same or different, and can be alkyl groups having 2 to 24 carbon atoms or (alkyl)aryl groups having 6 to 24 carbon atoms, preferably alkyl groups having 4 to 13 carbon atoms or (alkyl)aryl groups having 10 to 15 carbon atoms. The alkyl group can be any of primary, secondary, or tertiary alkyl groups, and can be straight-chain or branched. It should be noted that "(alkyl)aryl" refers to "aryl or alkylaryl". In alkylaryl groups, the substitution position of the alkyl group in the aromatic ring is arbitrary. 1 ~X 4 Each can be independently a sulfur atom or an oxygen atom, X 1 ~X 4 At least one of them is a sulfur atom.

[0064] Examples of molybdenum-based friction modifiers other than MoDTC include molybdenum dithiophosphate, molybdenum oxide, molybdate, ammonium salts and other molybdates, molybdenum disulfide, molybdenum sulfide, molybdate sulfide, and sulfur-containing molybdenum-based friction modifiers. Dialkylamine molybdates are preferred as molybdenum-based friction modifiers other than MoDTC.

[0065] When the internal combustion engine lubricating oil composition of the present invention contains a molybdenum-based friction modifier, the amount of molybdenum derived from the molybdenum-based friction modifier, based on the total amount of the composition, is preferably 50 ppm by mass or more and 2000 ppm by mass or less (more preferably 300 ppm by mass or more and 1800 ppm by mass or less, further preferably 500 ppm by mass or more and 1000 ppm by mass or less, and particularly preferably 600 ppm by mass or more and 850 ppm by mass or less). By setting the molybdenum content to the lower limit or above, fuel efficiency can be improved compared to cases below the lower limit. In addition, by setting the molybdenum content to the upper limit or below, the storage stability of the lubricating oil composition can be improved compared to cases exceeding the upper limit. The amount of molybdenum in the oil is determined according to JPI-5S-62 by inductively coupled plasma atomic emission spectrometry (intensity ratio method (internal standard method)).

[0066] Furthermore, the lubricating oil composition for internal combustion engines of the present invention preferably includes an ashless friction modifier. In this specification, an ashless friction modifier refers to a friction modifier that does not contain metallic elements. By including such an ashless friction modifier, the coefficient of friction of the composition can be reduced. There are no particular limitations on such an ashless friction modifier; known ashless friction modifiers can be appropriately used, for example, nitrogen-containing ashless friction modifiers, ashless friction modifiers composed of dithiocarbamates, zinc dithiocarbamates, disulfides, polysulfides, thioolefins, or thiogreases. In addition, such an ashless friction modifier can be used alone, or two or more can be used in any proportion. Furthermore, other types of ashless friction modifiers can also be appropriately included.

[0067] In addition, the nitrogen-containing ashless friction modifier is preferably selected from at least one of amino acid compounds, amine compounds, urea compounds, fatty acid ester compounds, and their derivatives having 12 to 30 carbon atoms, including alkyl, alkenyl, or acyl groups.

[0068] As suitable amino acid compounds for use as such nitrogen-containing ashless friction modifiers, compounds represented by the following formula (B) can be listed.

[0069] (B) Here, R in equation (B) 10 R is an alkyl, alkenyl, or acyl group having 12 to 30 carbon atoms. 11 R is an alkyl group or hydrogen atom having 1 to 4 carbon atoms. 12 It is hydrogen or an alkyl group having 1 to 10 carbon atoms. The alkyl group can contain straight-chain, branched, or cyclic structures, and the carbon atoms can be substituted with heteroatoms or modified with functional groups such as hydroxyl, carboxyl, or amino groups. R 13 The group is an alkyl group having 1 to 4 carbon atoms or hydrogen, where n is 0 or 1, and Y is a functional group having active hydrogen, a hydrocarbon having that functional group, a metal salt or ethanolamine salt of that functional group, or a methoxy group. The active hydrogen functional group of Y in formula (B) is preferably a hydroxyl or amino group.

[0070] Furthermore, considering the sustainability of the frictional properties effect, R is the preferred ashless friction modifier. 10 An acyl group (oleoyl group) with 18 carbon atoms, R 11 Methyl, R 12 Oleylsarcosine with hydrogen, hydroxyl group Y, and n = 0.

[0071] In addition, compounds represented by the following formula (C) can be listed as suitable amine compounds for use as nitrogen-containing ashless friction modifiers.

[0072] R 20 -(NR 21 )-R 22 (C) (R) 20 R is an alkyl, alkenyl, or acyl group having 12 to 30 carbon atoms. 21 R 22 (Each of which is independently hydrogen, alkyl, alkenyl, acyl, or hydroxyalkyl) Examples of amine compounds represented by formula (C) include oleylamine and stearylamine, with oleylamine being preferred. Additionally, 2,2'-(octadecane-1-ylimino)diethanol is also a preferred amine compound represented by formula (C).

[0073] Furthermore, as a suitable urea compound for use as the nitrogen-containing ashless friction modifier, a compound having a structure represented by the following formula (D) is preferred.

[0074] R 30 -NH-CO-NH2 (D) (R) 30 (Alkyl, alkenyl, or acyl groups having 12 to 30 carbon atoms) Such urea compounds are preferably aliphatic urea compounds, and more preferably octadecenylurea.

[0075] Suitable fatty acid ester compounds for use as the nitrogen-containing ashless friction modifier are any compounds formed by the esterification of the carboxyl group of a fatty acid with an alcohol, without particular limitation. Examples include esters of linear or branched fatty acids with aliphatic monohydric or polyhydric alcohols. The fatty acid can be saturated or unsaturated. The number of carbon atoms in these fatty acid ester compounds can be, for example, 7 to 31. As the fatty acid ester compound, esters of fatty acids and aliphatic polyhydric alcohols are preferred, more preferably esters of linear fatty acids and aliphatic polyhydric alcohols, and even more preferably esters of linear unsaturated fatty acids and aliphatic polyhydric alcohols. These aliphatic polyhydric alcohol esters can be complete esters or partial esters, preferably partial esters. As esters of these aliphatic polyhydric alcohols, glyceryl monooleate is preferred.

[0076] Regarding the alkyl, alkenyl, or acyl groups having 12 to 30 carbon atoms, which are suitable as the aforementioned compounds used as nitrogen-containing ashless friction modifiers, the number of carbon atoms in these groups is preferably 14 to 24, more preferably 16 to 20, and even more preferably 18. Such alkyl, alkenyl, or acyl groups having 12 to 30 carbon atoms are most preferably octadecyl, 9-octadecenyl, or oleoyl. The alkyl, alkenyl, or acyl groups can be linear or branched, but are preferably linear.

[0077] In addition, oleylsarcosine, oleylpropylenediamine, oleic acid, oleylamine, glyceryl monooleate, oleyl diethanolamine, N,N-diethanol oleamide, benzotriazole derivatives, and thioolefins are listed as suitable ashless friction modifiers. Among them, oleylsarcosine, oleylpropylenediamine, oleic acid, oleylamine, glyceryl monooleate, oleyl diethanolamine, N,N-diethanol oleamide, benzotriazole derivatives, and thioolefins are more preferred, oleylsarcosine, oleylpropylenediamine, oleic acid, and N,N-diethanol oleamide are even more preferred, and oleylsarcosine is particularly preferred.

[0078] When the internal combustion engine lubricating oil composition of the present invention contains an ashless friction modifier, the content of the ashless friction modifier, based on the total amount of the composition, is preferably 0.001% by mass or more and 5.0% by mass or less, more preferably 0.01% by mass or more and 1.0% by mass or less, and even more preferably 0.1% by mass or more and 0.5% by mass or less.

[0079] In the case where the internal combustion engine lubricating oil composition of the present invention includes an ashless friction modifier and the ashless friction modifier is a nitrogen-containing ashless friction modifier, the nitrogen content derived from the ashless friction modifier is preferably 10 ppm by mass or more and 500 ppm by mass or less (more preferably 50 ppm by mass or more and 400 ppm by mass or less, and even more preferably 100 ppm by mass or more and 300 ppm by mass or less). By setting the amount of nitrogen derived from the ashless friction modifier to 10 ppm by mass or more, the coefficient of friction can be reduced.

[0080] Furthermore, the lubricating oil composition for internal combustion engines of the present invention preferably contains an antioxidant. Known antioxidants such as phenolic antioxidants and amine-based ashless antioxidants can be used as such antioxidants. It should be noted that such antioxidants can be used alone or in combination of two or more in any proportion.

[0081] Examples of such phenolic antioxidants include 2,6-di-tert-butyl-4-methylphenol, 4,4'-methylenebis(2,6-di-tert-butylphenol), and octyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate.

[0082] In addition, amine-based ashless antioxidants can be used in the field of lubricating oil compositions for internal combustion engines. Alkyl diphenylamines having the following general formula (E) are preferred as amine-based ashless antioxidants.

[0083] In equation (E), R 60 and R 61 They can be the same or different, each representing a hydrogen atom or an alkyl group having 1 to 16 carbon atoms. Among them, R... 60 R 61 Not all of them will be hydrogen at the same time. As a product of R 60 and R 61 The alkyl group can be represented by methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, and hexadecyl (these alkyl groups can be straight-chain or branched), among which the preferred straight-chain alkyl group having 9 carbon atoms is nonyl.

[0084] When the internal combustion engine lubricating oil composition of the present invention contains an antioxidant, the content of the antioxidant is preferably 0.1% by mass or more and 5.0% by mass or less (more preferably 1.5% by mass or more and 3.0% by mass or less) based on the total amount of the composition.

[0085] Furthermore, the lubricating oil composition for internal combustion engines of the present invention preferably includes an anti-wear agent. There are no particular limitations on such an anti-wear agent, and known compounds used as anti-wear agents can be used in the lubricating oil composition. Examples of anti-wear agents include phosphorus-based and sulfur-phosphorus-based anti-wear agents. Examples of such anti-wear agents include phosphites, thiophosphites, dithiophosphites, trithiophosphites, phosphates, thiophosphates, dithiophosphates, trithiophosphates, their amine salts, their metal salts, and their derivatives. Such anti-wear agents can be used alone or in combination of two or more.

[0086] Furthermore, zinc dialkyl dithiophosphate (ZnDTP) or zinc dialkyl phosphate is preferred as the anti-wear agent. Among such zinc dialkyl dithiophosphates, compounds represented by the following formula (F) are preferred.

[0087] (F) R in the general formula (F) 80 ~R 83 Each of the components is an alkyl group, either linear or branched, having 1 to 24 carbon atoms. This alkyl group can be a primary alkyl group, a secondary alkyl group, or a tertiary alkyl group. As dialkyl zinc dithiophosphate, zinc dithiophosphate having a primary alkyl group (primary alkyl type ZnDTP) or zinc dithiophosphate containing a secondary alkyl group (secondary alkyl type ZnDTP) is preferred. In particular, to improve wear resistance, dialkyl zinc dithiophosphate with secondary alkyl zinc dithiophosphate as the main component is preferred. Furthermore, when primary alkyl type ZnDTP and secondary alkyl type ZnDTP are used in combination, their mass ratio ([primary alkyl type ZnDTP]:[secondary alkyl type ZnDTP]) is preferably 80:20 to 10:90, more preferably 30:70 to 20:80.

[0088] When the internal combustion engine lubricating oil composition of the present invention contains an anti-wear agent, the content of the anti-wear agent, based on the total amount of the composition, is preferably 0.1% by mass or more and 1.6% by mass or less (more preferably 0.9% by mass or more and 1.5% by mass or less). Furthermore, when the internal combustion engine lubricating oil composition of the present invention contains an anti-wear agent composed of a phosphorus-containing compound, the amount of phosphorus derived from the anti-wear agent, based on the total amount of the composition, is preferably 10 ppm by mass or more and 900 ppm by mass or less (more preferably 600 ppm by mass or more and 800 ppm by mass or less, and even more preferably 750 ppm by mass or more and 785 ppm by mass or less).

[0089] Furthermore, the lubricating oil composition for internal combustion engines of the present invention preferably contains a dispersant. There are no particular limitations on such a dispersant; known ashless dispersants can be appropriately used (for example, see Japanese Patent Application Publication No. 2022-158121, Japanese Patent Application Publication No. 2003-155492, Japanese Patent Application Publication No. 2020-76004, International Publication No. 2013 / 147162, etc.), such as succinimides and their derivatives, or benzylamine, etc. Additionally, such a succinimid can be either a boron-free succinimid or a boron-containing succinimid, preferably a boron-free succinimid. By using a boron-free succinimid, the increase in sulfate ash content due to the increase in boron can be prevented. It should be noted that boron-free succinimide refers to succinimide in which some or all of the amino and / or imino groups are not neutralized or amidated by boric acid or similar substances. For example, based on succinimide, the boron content is less than 0.1% by mass. It should also be noted that such ashless dispersants can be used alone or in combination of two or more in any proportion.

[0090] When the internal combustion engine lubricating oil composition of the present invention contains a dispersant, the content of the dispersant, based on the total amount of the composition, is preferably 2.0% by mass or more and 7.0% by mass or less (more preferably 2.8% by mass or more and 3.6% by mass or less). When the internal combustion engine lubricating oil composition of the present invention contains a dispersant and the dispersant is succinimidyl or a derivative thereof, the amount of nitrogen derived from the dispersant, based on the total amount of the lubricating oil composition, is preferably 350 ppm by mass or more and 2000 ppm by mass or less (more preferably 370 ppm by mass or more and 980 ppm by mass or less, and even more preferably 400 ppm by mass or more and 600 ppm by mass or less). By ensuring that the amount of nitrogen derived from succinimidyl or a derivative thereof is within the aforementioned range, low sulfuric acid ash content and detergency can be ensured.

[0091] Furthermore, the lubricating oil composition for internal combustion engines of the present invention may contain a pour point depressant. Known pour point depressants can be used as such depressants without particular limitation; for example, polymethyl methacrylate (PMA) and ethylene-vinyl acetate copolymer (EVA) are preferred. Furthermore, from the viewpoint of pour point depressing effect and shear stability, polymers such as PMA and EVA used as the pour point depressant are preferably polymers with a weight-average molecular weight of 10,000 to 200,000. One pour point depressant may be used alone, or two or more may be used in combination. In addition, when a pour point depressant is used, its content, based on the total amount of the lubricating oil composition, is preferably 0.01 to 1.0% by mass (more preferably 0.03 to 0.6% by mass).

[0092] Furthermore, the lubricating oil composition for internal combustion engines of the present invention may contain an antiemulsifier. Such an antiemulsifier may be, for example, a known antiemulsifier such as a polyalkylene glycol-based nonionic surfactant. Additionally, an antiemulsifier may be used alone or in combination of two or more. When an antiemulsifier is used in the lubricating oil composition, its content is preferably 0.005 to 5.0% by mass based on the total amount of the composition.

[0093] Furthermore, the lubricating oil composition for internal combustion engines of the present invention may contain a metal passivating agent. There are no particular limitations on such metal passivating agents; examples include imidazoline, pyrimidine derivatives, alkylthiadiazoles, mercaptobenzothiazoles, benzotriazoles or derivatives thereof, tolyltriazoles or derivatives thereof, 1,3,4-thiadiazole polysulfides, 1,3,4-thiadiazolyl-2,5-bis(dialkyldithiocarbamate), 2-(alkyldithio)benzimidazole, β-(o-carboxybenzylthio)propionitrile, etc. One metal passivating agent may be used alone, or two or more may be used in combination. Furthermore, when using a metal passivating agent, its content is preferably 0.01 to 0.5% by mass (more preferably 0.02 to 0.3% by mass) based on the total amount of the composition.

[0094] Furthermore, the lubricating oil composition for internal combustion engines of the present invention may contain an antifoaming agent. Such antifoaming agents include, for example, known antifoaming agents such as siloxanes, fluorosiloxanes, and fluoroalkyl ethers. Additionally, when using an antifoaming agent, its content is preferably 0 to 0.5% by mass (more preferably 0 to 0.1% by mass). It should be noted that the lower limit of the content is not particularly limited, and in one embodiment it can be 0.0001% by mass or more.

[0095] In the lubricating oil composition for internal combustion engines of the present invention, the contents of calcium, magnesium, sulfur, boron, and nitrogen relative to the total amount of the composition are preferably within the numerical ranges described below. Specifically, from the viewpoint of preventing premature ignition in the low-rotation, high-load region and maintaining cleanliness, the calcium content, based on the total amount of the composition, is preferably 10 ppm by mass or more and 1800 ppm by mass or less, more preferably 1000 ppm by mass or more and 1540 ppm by mass or less. Furthermore, from the viewpoint of maintaining cleanliness and maintaining friction-reducing properties, the magnesium content, based on the total amount of the composition, is preferably 10 ppm by mass or more and 1600 ppm by mass or less, more preferably 200 ppm by mass or more and 501 ppm by mass or less. From the viewpoint of maintaining cleanliness and maintaining wear resistance, the sulfur content, based on the total amount of the composition, is preferably 100 ppm by mass or more and 4500 ppm by mass or less, more preferably 800 ppm by mass or more and 2600 ppm by mass or less. From the viewpoint of maintaining fuel-efficient performance, the boron content, based on the total composition, is preferably 0 ppm or more and 900 ppm or less, more preferably 0 ppm or more and 600 ppm or less. The nitrogen content, based on the total composition, is preferably 800 ppm or more, more preferably 900 ppm or more and 1650 ppm or less. It should be noted that the contents of calcium, magnesium, sulfur, and boron are values ​​determined according to JIS K0116 by inductively coupled plasma atomic emission spectrometry (intensity ratio method (internal standard method)), and the nitrogen content (ppm by mass) is the value determined according to JIS K2609.

[0096] Furthermore, the lubricating oil composition for internal combustion engines of the present invention contains a lubricating oil base oil, wherein the kinematic viscosity of the lubricating oil base oil at 40°C is 18.0 mm. 2 The lubricating oil composition is free of olefin copolymers and the calculated value X obtained by formula (1) is less than 0.45% by mass per hour. Other properties are not particularly limited.

[0097] The kinematic viscosity of the lubricating oil composition for internal combustion engines of the present invention at 100°C is preferably 4.5 mm. 2 / s or higher and 9.3mm 2 / s or less (more preferably 4.8mm) 2 / s or higher and 7.8mm 2 (below / s). Furthermore, the kinematic viscosity of the internal combustion engine lubricating oil composition of the present invention at 40°C is preferably 26.0 mm. 2 / s or less (more preferably 16.0mm) 2 / s or higher and 23.0mm 2 / s or less, and more preferably 19.0mm. 2 / s or higher and 22.0mm 2 (below / s). By setting the kinematic viscosity of the lubricating oil composition to below the upper limit, excellent fuel-saving performance can be obtained. In addition, by setting the kinematic viscosity of the lubricating oil composition to above the lower limit, the oil film formation at the lubrication points is excellent, and the evaporation loss of the lubricating oil composition can be further reduced.

[0098] The viscosity index of the lubricating oil composition for internal combustion engines of the present invention is preferably 120 or higher and 450 or lower (more preferably 138 or higher and 380 or lower). By setting the viscosity index of the lubricating oil composition to the lower limit or higher, fuel efficiency can be improved. Furthermore, by setting the viscosity index of the lubricating oil composition to the upper limit or lower, detergency can be improved. It should be noted that in this specification, "viscosity index" refers to a value measured according to JIS K 2283-1993.

[0099] The CCS viscosity of the lubricating oil composition for internal combustion engines of the present invention at -40°C is preferably 7000 mPa·s or less (more preferably 6200 mPa·s or less, further preferably 5700 mPa·s or less, and most preferably 4000 mPa·s or less). If such a CCS viscosity at -40°C exceeds the upper limit, there is a tendency for increased losses due to viscous resistance in low-temperature environments below the normal temperature range, and the viscosity at low temperatures becomes excessive relative to temperature changes. This leads to excessive changes in the oil film and fluid delivery state during the oil temperature rise process accompanying the operation of the internal combustion engine, thereby tending to impair stable operation. Furthermore, the CCS viscosity of the lubricating oil composition for internal combustion engines of the present invention at -35°C is preferably 5000 mPa·s or less (more preferably 4000 mPa·s or less, further preferably 3500 mPa·s or less, and most preferably 2800 mPa·s or less). If the CCS viscosity at -35°C exceeds the upper limit, the viscous resistance becomes excessive during operation of the internal combustion engine in low-temperature environments below room temperature, tending to impair fuel efficiency. It should be noted that the CCS viscosity at -35°C is the value measured according to ASTM D5293 at a test temperature of -35°C, and the CCS viscosity at -40°C is the value measured using the same method as the ASTM D5293 method, except that the test temperature is changed to -40°C.

[0100] The HTHS viscosity of the internal combustion engine lubricating oil composition of the present invention at 150°C is preferably 1.7 mPa·s or more and 2.8 mPa·s or less (more preferably 2.3 mPa·s or more and 2.5 mPa·s or less). Good fuel economy is achieved by setting the HTHS viscosity at 150°C to the upper limit or below. Furthermore, good lubricity is achieved by setting the HTHS viscosity at 150°C to the lower limit or above.

[0101] The HTHS viscosity of the internal combustion engine lubricating oil composition of the present invention at 100°C is preferably 3.0 mPa·s or more and 5.0 mPa·s or less (more preferably 3.6 mPa·s or more and 4.7 mPa·s or less). Furthermore, the HTHS viscosity of the internal combustion engine lubricating oil composition of the present invention at 80°C is preferably 4.6 mPa·s or more and 6.7 mPa·s or less (more preferably 5.0 mPa·s or more and 6.4 mPa·s or less). It should be noted that the HTHS viscosity at 150°C or 100°C represents the high-temperature high-shear viscosity at each temperature (150°C or 100°C) specified in ASTM D4683, and the HTHS viscosity at 80°C represents the high-temperature high-shear viscosity measured using the same method as the test method specified in ASTM D 4683, except that the test temperature is changed to 80°C.

[0102] Furthermore, the lubricating oil composition for internal combustion engines of the present invention is preferably classified as any one of 0W-8, 0W-12, 0W-16, and 0W-20 in the viscosity grades specified in the J300 standard of the Society of Automotive Engineers (hereinafter referred to as "SAE viscosity grades"), and is particularly preferred to be classified as any one of 0W-16 and 0W-20.

[0103] The sulfuric acid ash content of the lubricating oil composition for internal combustion engines of the present invention is preferably 1.00% by mass or less (more preferably 0.90% by mass or less). Here, "sulfuric acid ash content" refers to the sulfuric acid ash content measured according to ASTM D874. It should be noted that in the lubricating oil composition for internal combustion engines, if the amount of metal increases, the sulfuric acid ash content increases, and if the sulfuric acid ash content increases, there is a tendency for the filter life to decrease. From this point of view, it is preferable that the sulfuric acid ash content is below the aforementioned upper limit.

[0104] The evaporation loss (NOACK (250°C, 1 hour) evaporation loss) of the internal combustion engine lubricating oil composition of the present invention, determined by NOACK evaporation test according to ASTM D5800 at 250°C for 1 hour, is preferably 10.0 to 30.0% by mass (more preferably 12.0 to 30.0% by mass, even more preferably 16.0 to 30.0% by mass, particularly preferably 21.0 to 29.5% by mass). By setting the NOACK (250°C, 1 hour) evaporation loss to below the upper limit, there is a tendency to obtain a higher effect in terms of low evaporation; on the other hand, by setting it to above the lower limit, there is a tendency to obtain a higher effect in terms of improved fuel efficiency.

[0105] Furthermore, the internal combustion engine lubricating oil composition of the present invention is based on the test method specified in ASTM D5800, and a NOACK evaporation test is conducted at a temperature of 150°C. Every 4 hours, the test is temporarily stopped, and a cooling procedure specified in the test method is performed. After confirming the quality, the test is restarted. This process is repeated three times at 150°C for 4 hours. When calculating the change in NOACK evaporation loss per unit time (slope) between 4 hours and 12 hours based on the evaporation loss (mass%) of the third NOACK evaporation test (after 12 hours) with a total test time of 12 hours and the evaporation loss (mass%) of the first NOACK evaporation test (after 4 hours) with a test time of 4 hours, this change is preferably 0.45 mass% / hour or less (more preferably 0.35 mass% / hour or less). By setting such a change in NOACK evaporation loss per unit time to below the aforementioned upper limit, a higher level of reduction in evaporability can be achieved.

[0106] The content of the component with a boiling point of 330°C or less in the lubricating oil composition for internal combustion engines of the present invention is more preferably 4.6% by mass or less (more preferably 2.9% by mass or less) based on the total amount of the composition. By setting the content of such a component with a boiling point of 330°C or less to the above-mentioned upper limit, evaporation loss during use can be further reduced, and a higher effect can be obtained in terms of low volatility. It should be noted that the content of such a component with a boiling point of 330°C or less can be determined as follows: the lubricating oil composition is subjected to the aforementioned "gas chromatographic distillation test (A)," and the content ratio of the component with a boiling point of 330°C or less relative to the total amount of the lubricating oil base oil is calculated from the obtained gas chromatogram.

[0107] The content of the component with a boiling point of 310°C or less in the lubricating oil composition for internal combustion engines of the present invention is more preferably 3.2% by mass or less (more preferably 2.0% by mass or less) based on the total amount of the composition. By setting the content of such a component with a boiling point of 310°C or less to the above-mentioned upper limit, evaporation loss during use can be further reduced, and a higher effect can be obtained in terms of low volatility. It should be noted that the content of such a component with a boiling point of 310°C or less can be determined as follows: the lubricating oil composition is subjected to the aforementioned "gas chromatographic distillation test (A)," and the content ratio of the component with a boiling point of 310°C or less relative to the total amount of the lubricating oil base oil is calculated based on the obtained gas chromatogram.

[0108] Furthermore, the lubricating oil composition for internal combustion engines of the present invention can be used in devices equipped with internal combustion engines without particular limitation. Specifically, it can be used as a lubricating oil composition for automobile engines equipped with GPF (gasoline particulate filter) and a lubricating oil composition for hybrid vehicles equipped with internal combustion engines and electric motors.

[0109] [Method for manufacturing lubricating oil composition for internal combustion engines] The method for manufacturing the lubricating oil composition for internal combustion engines of the present invention is a method for manufacturing a lubricating oil composition for internal combustion engines containing a lubricating oil base oil. It is a method of manufacturing the lubricating oil composition for internal combustion engines by designing its composition in such a way that the kinematic viscosity of the lubricating oil base oil at 40°C is 18.0 mm. 2 The lubricating oil composition is free of olefin copolymers, and the estimated value X of the change in evaporation loss per unit time of the lubricating oil composition determined by the NOACK evaporation test at 150°C for 12 hours, calculated by formula (1), is 0.45 wt% / hour or less (assuming the estimated value X of the change in NOACK evaporation loss per unit time of the lubricating oil composition measured at 150°C for 12 hours). It should be noted that the internal combustion engine lubricating oil composition obtained by this invention is the same as the internal combustion engine lubricating oil composition of this invention.

[0110] Thus, the method for manufacturing the lubricating oil composition for internal combustion engines of the present invention obtains the lubricating oil composition for internal combustion engines by designing the composition in such a way that the kinematic viscosity of the lubricating oil base oil used in the manufacture of the composition at 40°C is 18.0 mm. 2The lubricating oil composition should be free of olefin copolymers and the calculated value X obtained by formula (1) should be less than 0.45 wt% / hour. It should be noted that, in the lubricating oil composition for internal combustion engines, as mentioned above, the reduction of viscosity for improving fuel efficiency and the reduction of evaporation loss for improving long service life are mutually exclusive properties. Here, for example, when the desired design of the base oil is manufactured by separating the fractions through distillation, and the composition is used therein, it is a matter that should be studied from an industrial point of view in terms of economic rationality, such as the design of the composition based on which boiling point the heavy components and the light components are strictly separated. Here, the method that means that the process of manufacturing the preferred lubricating oil composition is subject to chance is incompatible with the existence of modern industry that utilizes the laws of nature, is to randomly manufacture multiple compositions having different boiling points for each component and having a distribution of boiling points over a very wide range, to conduct tests (oil consumption tests) related to evaporation loss on all of them, and to manufacture the preferred lubricating oil composition by chance based on the results. Therefore, in order to rationally design and predict the distribution within the desired boiling point range in the overall composition, the inventors have repeatedly conducted research and, as described above, derived a parameter, X, calculated from Equation (1), which has a very high correlation with the actual evaporation loss. Furthermore, based on this parameter, X, the desired composition can be easily designed, thereby enabling efficient and reliable manufacturing of the desired composition. Therefore, the inventors believe that the manufacturing method of the present invention, utilizing this parameter, can further accelerate industrial development. It should be noted that the application value of the present invention is not limited to the matters described above; for example, it can also contribute to aspects of sustainable business planning considered important in modern industries. Generally, in industries utilizing global logistics, the substitutability of raw materials is important due to abnormal weather conditions accompanying climate change and geopolitical risks. In contrast, by utilizing this invention, for example, in cases where a base oil having the most preferred boiling point distribution for the composition is unavailable, it is easy to design combinations of alternative base oils, thus facilitating the adoption of suboptimal strategies. Therefore, it is also easy to prepare substitutes for lubricating oil compositions having the preferred boiling point distribution, and the business can be continuously carried out. In this way, it is easy to design lubricating oil compositions with desired properties and lubricating oil compositions with the same properties. Therefore, from the viewpoint of continuously manufacturing desired compositions, this invention is also highly advantageous.

[0111] It should be noted that the composition is designed to achieve a kinematic viscosity of 18.0 mmHg for the base oil at 40°C. 2When the calculated value X of the change in NOACK evaporation loss per unit time of the lubricating oil composition, as determined by formula (1) under the assumed conditions of 150°C and 12 hours, is less than 0.45 wt% / hour, the composition can be designed by considering the boiling point and distribution of the components used, and by appropriately combining known additives other than olefin copolymers as needed, to make the calculated value X obtained by formula (1) less than 0.45 wt% / hour. The composition can be easily designed (executed) and manufactured by obtaining gas chromatographic distillation data of the base oil and additive components. It should be noted that the same components as those described in the above-described internal combustion engine lubricating oil composition of the present invention can be appropriately used as the various components used to manufacture such a composition, depending on its design. Furthermore, in the manufacturing method of such an internal combustion engine lubricating oil composition, particularly when the lubricating oil composition is manufactured by mixing after sequentially adding all necessary components, compared to the manufacturing method of obtaining a lubricating oil composition by adding only additives other than the base oil to the lubricating oil base oil, a manufacturing method is more preferable as follows: In a stage (process) near its final step where at least 90% by mass of the components based on the total amount of the lubricating oil composition are added, a monomer premixed with the base oil component or a mixture of the base oil component and one or more other additives is added to the mixture of at least 90% by mass of the components based on the total amount of the lubricating oil composition and mixed to obtain the lubricating oil composition. This allows for more precise adjustments to the manufacturing process based on gas chromatographic distillation data of the base oil monomer or the mixture containing the base oil, which has a large proportion in the composition and a significant impact on the estimated value (estimated value) X.

[0112] Example The present invention will now be described in more detail based on embodiments and comparative examples, but the present invention is not limited to the following embodiments.

[0113] (Regarding the ingredients used in the various embodiments, etc.) First, Table 1 shows the abbreviations, types, and characteristics of the base oil components used in each example, and Table 2 shows the abbreviations, types, and characteristics of the additives used in each example. It should be noted that in the examples described below, the components are sometimes referred to using the abbreviations listed in Tables 1 and 2. Furthermore, the "content of components with a boiling point below 330°C" for the base oil components shown in Table 1 indicates the content of components with a boiling point below 330°C in the base oil, determined by the same test as the "Gas Chromatography Distillation Test (A)" described above. Additionally, the "kinematic viscosity at 40°C" and "kinematic viscosity at 100°C" shown in Table 1 are values ​​measured according to ASTM D-445. It should be noted that the "NOACK (250°C, 1 hour) evaporation loss" shown in Table 1 indicates the evaporation loss of each base oil determined by the NOACK evaporation test under conditions of 250°C and 1 hour according to ASTM D5800. Here, for base oils with a NOACK (250°C, 1 hour) evaporation loss exceeding 60% by mass, direct measurement is not possible. Therefore, an estimated value is used, which is obtained by preparing three or more samples consisting of mixtures of other base oils with known NOACK (250°C, 1 hour) evaporation losses in different proportions. The NOACK (250°C, 1 hour) evaporation loss of each sample is calculated, and the estimated value is calculated by obtaining an approximate straight line based on the measured value.

[0114] (Examples 1-43 and Comparative Examples 1-9) Using the components shown in Tables 3-7, lubricating oil compositions of Examples 1-43 and Comparative Examples 1-9 were prepared respectively. It should be noted that, regarding the items "Content of base oil component in lubricating oil base oil" and "Content of additive in lubricating oil composition" in Tables 3-7, blank columns indicate that the component was not used. Furthermore, in the items "Content of base oil component in lubricating oil base oil," "Characteristics of lubricating oil base oil," and "Content of additive in lubricating oil composition" in Tables 3-7, "mass%" indicates the content (mass%) relative to the total amount of lubricating oil base oil, and "by mass%" indicates the content (mass%) relative to the total amount of the lubricating oil composition. It should be noted that the values ​​(unit: by mass%) of the viscosity index improvers (PMA series VI (1) to (5) and OCP series VI) in Tables 3 to 7 represent the content of the resin component (polymer component with a molecular weight of 1000 or more) constituting the viscosity index improver based on the total amount of the composition (content of the viscosity index improver converted to resin component). Tables 3 to 7 also show the content (mass ppm: mass ppm) of each element (Ca, Mg, Mo, P, Zn, S and B) in the composition as determined by inductively coupled plasma atomic emission spectrometry (intensity ratio method (internal standard method)) according to JIS K0116, and the nitrogen content (mass ppm: mass ppm) as determined according to JIS K2609.

[0115] [Evaluation of the properties of the lubricating oil compositions obtained in each embodiment] <Gas Chromatography Distillation Test> The lubricating oil compositions obtained in each example were subjected to the same test as described in the "Gas Chromatography Distillation Test (A)" above, and gas chromatograms were obtained. Then, based on the gas chromatograms, the contents of components with boiling points below 240°C and components with boiling points in the range of {(i-1)×10}°C to (i×10)°C (where i is an integer from 25 to 60, and all values ​​were measured separately) were determined (unit: mass %: mass ratio based on the total amount of the composition). It should be noted that, as can be seen from the compositions shown in Tables 3 to 7, the lubricating oil compositions obtained in each example do not contain components with boiling points above 600°C. Therefore, the contents of components with boiling points above 600°C were not measured (it can be seen that the contents of components with boiling points in the range of {(i-1)×10}°C to (i×10)°C and where i is 61 to 75 are all 0% by mass, and there is no significance in measuring them, so the measurement was omitted). Furthermore, the contents (total) of components with boiling points below 310°C and below 330°C in the lubricating oil composition were determined based on the gas chromatogram. As the results of this gas chromatographic distillation test (A), the contents of components with boiling points between {(i-1)×10}°C and (i×10)°C (where i is an integer from 25 to 60) are shown in Tables 8 to 11. The contents (total) of components with boiling points below 310°C and below 330°C are shown in Tables 12 to 15. Components with a measured content less than 0.01% by mass are considered to have a content of 0 and are recorded as 0.00 in Tables 8 to 11. It should be noted that the contents of components with boiling points below 240°C in the lubricating oil composition measured are all 0.00% by mass.

[0116] <Calculation of the estimated value X> For the lubricating oil compositions obtained in the various embodiments, the estimated value X of the change in NOACK evaporation loss per unit time of the lubricating oil composition was calculated using the gas chromatographic distillation results shown in Tables 8 to 11, according to equations (1) to (3). In this calculation, for i values ​​of 61 or higher, the value of A(i) was taken as 0. The results are shown in Tables 12 to 15. It should be noted that in this specification, lubricating oil compositions with an estimated value X of 0.45 wt% / hour or less are considered to have a high level of low evaporability, while lubricating oil compositions with an estimated value X exceeding 0.45 wt% / hour are considered to have a low level of low evaporability.

[0117] <Determination of Kinematic Viscosity and Viscosity Index> For the lubricating oil compositions obtained in each of the embodiments and the like, the kinematic viscosity at 40°C (40°C kinematic viscosity) and the kinematic viscosity at 100°C (100°C kinematic viscosity) were measured respectively in accordance with ASTM D-445. In addition, for the lubricating oil compositions obtained in each of the embodiments and the like, the "viscosity index" was in accordance with JIS K 2283-1993. The results obtained are shown in Tables 12 to 15. It should be noted that when the kinematic viscosity at 40°C is 26.0 mm 2 / s or less, it can be evaluated that the kinematic viscosity in the low-temperature region is sufficiently low.

[0118] <Measurement of high-temperature high-shear viscosity (HTHS viscosity)> For the lubricating oil compositions obtained in each of the embodiments and the like, the high-temperature high-shear viscosity (HTHS viscosity) at each of the temperatures of 150°C, 100°C, and 80°C was measured. It should be noted that the HTHS viscosity at 150°C or 100°C represents the high-temperature high-shear viscosity at each of the temperatures (150°C or 100°C) specified in ASTM D4683, and the HTHS viscosity at 80°C represents the high-temperature high-shear viscosity measured by the same method as the measurement method specified in ASTM D 4683 except that only the test temperature is changed to 80°C. The results obtained are shown in Tables 12 to 15.

[0119] <Measurement method of low-temperature starting (CCS) viscosity> For the lubricating oil compositions obtained in each of the embodiments and the like, the CCS viscosity at -35°C was measured in accordance with ASTM D5293, and the CCS viscosity at -40°C was measured by the same method as the measurement method of the CCS viscosity in accordance with ASTM D5293 except that only the temperature condition is changed to -40°C. In addition, using the measurement results, the change amount of the CCS viscosity with respect to the temperature change amount from -35°C to -4°C (the change amount of the CCS viscosity per 1°C (the increase amount per 1°C decrease)) and the ratio of the CCS viscosities ( [CCS viscosity at -40°C] / [CCS viscosity at -35°C] ) were obtained together. The results obtained are shown in Tables 12 to 15.

[0120] <Measurement of acid value, base number (hydrochloric acid method), and base number (perchloric acid method)> For the lubricating oil compositions obtained in each of the embodiments and the like, the acid value, base number (hydrochloric acid method), and base number (perchloric acid method) were measured respectively in accordance with JIS K2501:2003. The results obtained are shown in Tables 12 to 15.

[0121] <Measurement of USV viscosity> For the lubricating oil compositions obtained in each of the embodiments and the like, at each of the temperatures of 40°C and 60°C, using a USV viscometer manufactured by PCS Instruments, at a shear rate of 1×106 The USV viscosity was measured under the condition of / s. The obtained results are shown in Tables 12 to 15.

[0122] <Determination of Sulfated Ash> For the lubricating oil compositions obtained in each of the embodiments, etc., the sulfated ash (mass %) was determined in accordance with JIS K2272. The obtained results are shown in Tables 12 to 15.

[0123] <Determination of NOACK Evaporation Loss> For the lubricating oil compositions obtained in each of the embodiments, etc., the NOACK evaporation loss was determined as follows. That is, first, for each sample of the compositions, three tests were performed that were the same as the NOACK volatility test specified in ASTM D5800 except that the temperature condition was changed to 150 °C and the test time was changed to 4 hours. These three tests were performed as follows: every 4 hours of the test time, the test was temporarily stopped, and after performing the cooling process specified in this test method (the NOACK volatility test specified in ASTM D5800), the mass was confirmed and the test was restarted. By operating in this way, for each sample, the NOACK volatility test under the conditions of 150 °C and 4 hours was performed three times intermittently (in the manner of performing a cooling process, measuring the mass, and restarting every 4 hours). Then, the evaporation loss (mass %) of NOACK (150 °C, 12 hours) in the third NOACK volatility test (after 12 hours) with a total test time of 12 hours and the evaporation loss (mass %) of NOACK (150 °C, 4 hours) in the first NOACK volatility test (after 4 hours) with a test time of 4 hours were respectively determined, and the change amount of the NOACK evaporation loss per unit time between 4 hours and 12 hours of the test time (hereinafter, sometimes referred to as "the slope of NOACK at 150 °C", unit: mass % / hour) was determined. It should be noted that when the slope of NOACK at 150 °C is 0.45 mass % / hour or less, the evaporation loss does not occur rapidly, and it can be evaluated as low volatility. The obtained results are shown in Tables 12 to 15. In addition, for the lubricating oil compositions obtained in each of the embodiments, etc., in addition to the above tests, the NOACK volatility test specified in ASTM D5800 was performed under the conditions of 250 °C and 1 hour, and the evaporation loss (mass %) of the lubricating oil composition was determined. The obtained results are shown in Tables 12 to 15.

[0124] <Evaluation of Characteristics of Oxidized Degraded Oil by ISOT Test> For the lubricating oil compositions obtained in the various embodiments, firstly, unused samples (new oil) were oxidized using the ISOT method (Indiana Stirring Oxidation Test) specified in JISK 2514-1 at a temperature of 165°C for 168 hours to obtain oxidized deteriorated oil. Next, using this oxidized deteriorated oil obtained by the ISOT method, the kinematic viscosity at 40°C, acid value, base value (hydrochloric acid method), and base value (perchloric acid method) were measured using the same method as described above. The results are shown in Tables 12-15, which present the increase rate (%) of the kinematic viscosity at 40°C after ISOT relative to the kinematic viscosity at 40°C of the new oil, the increase in acid value after ISOT, the increase in base value after ISOT (hydrochloric acid method), the increase in base value after ISOT (perchloric acid method), and the increase in acid value after ISOT.

[0125] <Evaluation based on heat pipe testing (evaluation of high-temperature cleaning performance)> For the lubricating oil compositions obtained in the various embodiments, a heat pipe test (HTT) was conducted according to JPI-5S-55-99 at a sample volume of 5 mL, a test temperature of 280°C, and a test time of 16 hours to evaluate high-temperature detergency. It should be noted that the HTT score ranges from a maximum of 10 points to a minimum of 0 points; a higher score indicates higher high-temperature detergency. The results are shown in Tables 12-15.

[0126] <Determination of the coefficient of friction (SRV test)> For the lubricating oil compositions obtained in the various embodiments, the SRV test was performed to determine the coefficient of friction as follows. First, using an SRV testing machine manufactured by OPTIMOL, standard test pieces according to ASTM D5706 were prepared [test pieces consisting of a cylinder (dimensions: 15 mm (diameter) × 22 mm) and a disc (dimensions: 24 mm (diameter) × 6.9 mm)]. Each lubricating oil composition was dropped onto the sliding surface of the test piece. The test was conducted at temperatures of 120°C and 40°C, under conditions of a load of 400 N, a vibration frequency of 50 Hz, an amplitude of 1.5 mm, and a test time of 15 minutes. The average coefficient of friction was measured from 10 minutes after the start of the test to 15 minutes after the start of the test (the test time was 10 to 15 minutes). The results are shown in Tables 12 to 15.

[0127] As shown in Tables 3-15, the composition and experimental results indicate that the kinematic viscosity of the lubricating oil base oil at 40℃ is 18 mm. 2 The lubricating oil compositions manufactured in Examples 1 to 43, which have a kinematic viscosity of 26.0 mmHg or less, an estimated value X of 0.45% by mass per hour or less, and do not contain olefin copolymers, were confirmed to have a kinematic viscosity of 26.0 mmHg at 40°C. 2 The kinematic viscosity is sufficiently low at low temperatures and below / s, and the change in NOACK evaporation loss per unit time (the slope of NOACK at 150°C) is less than 0.45% / hour for test times ranging from 4 to 12 hours. Therefore, it can be seen that the evaporation loss suppression effect during use is high, indicating that it is at a high level in terms of low volatility.

[0128] In contrast, the kinematic viscosity of the lubricating oil base oil at 40°C is 18 mm. 2 The lubricating oil compositions manufactured in Comparative Examples 1-9, which meet at least one of the following conditions: a viscosity of ≤0.5 g / s, a calculated value X of ≤0.45 wt% / hour, and a condition not containing olefin copolymers, do not satisfy the requirement of a kinematic viscosity of 26.0 mm at 40°C, as determined by test results. 2 It is impossible to achieve both low evaporation and low viscosity characteristics under conditions below / s and conditions where the slope of NOACK at 150°C is below 0.45 mass% / hour.

[0129] It should be noted that, based on the composition and experimental results shown in Tables 3-15, it can be confirmed that the lubricating oil composition manufactured in Example 1 is a composition with an SAE viscosity grade of 0W-16. Furthermore, if the lubricating oil compositions manufactured in Examples 1-4 are compared with each other, they differ in their composition in setting the content of the Mo compound within different ranges, but the slope of the NOACK at 150°C is all below 0.45% by mass / hour. Therefore, it can be seen that, in order to meet the requirement of a kinematic viscosity of 18 mmHg for the lubricating oil base oil at 40°C... 2 The composition is designed in a manner that ensures the composition has a concentration of less than 0.45% by mass per hour and does not contain olefin copolymers, thereby obtaining the desired properties such as detergency, detergency maintenance, and reduced intermetallic friction. The composition can be designed with appropriate adjustment of the content of the additives (Mo compounds) used.

[0130] It should be noted that, compared with Example 1, Examples 5 and 6 differ in the combination of base oil components, resulting in lubricating oil compositions with a further reduction in the estimated value X. This confirms a further reduction in the change in NOACK evaporation loss per unit time (the slope of NOACK at 150°C) between 4 and 12 hours of testing, and also indicates a further reduction in the kinematic viscosity of the composition at 40°C, demonstrating further superior fuel-saving performance. The lubricating oil compositions manufactured in Examples 7 and 8 are SAE viscosity grade 0W-8 compositions. The difference from the composition in Example 1 is that PMA-based viscosity index improvers are not used in Example 7, while the amount of PMA-based viscosity index improver used is changed in Example 8; however, the kinematic viscosity of the compositions at 40°C remains 26.0 mm. 2 The velocity per second (V / s) and the slope of the NOACK at 150°C were all below 0.45% by mass per hour. Furthermore, the lubricating oil compositions prepared in Examples 9 and 10 differed from those in Example 1 in that the types and amounts of detergents and antioxidants were changed, but the kinematic viscosity of the compositions at 40°C was still 26.0 mm. 2 The NOACK slope at 150°C is below 0.45% / hour (mass%), indicating that the types and amounts of detergents and antioxidants can be appropriately modified according to the product design without compromising volatility or fuel efficiency, thereby improving detergency and detergency maintenance. Furthermore, compared to Example 1, the lubricating oil compositions manufactured in Examples 11-15 mainly differed in the composition of the base oil; the kinematic viscosity of the lubricating oil base oil at 40°C was 18 mm. 2 With a viscosity-temperature characteristic (viscosity-temperature characteristic, kinematic viscosity at 40°C) of less than / s and an estimated value X of less than 0.45 wt% / hour, the slope of NOACK at 150°C is less than 0.45 wt% / hour (for Examples 11-15, compared to Example 1, the kinematic viscosity of the lubricating oil base oil at 40°C is particularly lower, thus the kinematic viscosity of the composition at 40°C is further lower). The results from the lubricating oil compositions manufactured in Examples 11-14 show that by improving the viscosity-temperature characteristic (kinematic viscosity at 40°C) of the lubricating oil base oil, the fuel-saving performance of the composition can be improved. Therefore, changing the viscosity-temperature characteristic is one of the appropriate options when designing compositions considering economic rationality.

[0131] In contrast, for calculated values ​​X below 0.45 wt% / hour but with a kinematic viscosity of over 18 mm at 40°C for the lubricating oil base oil, the value is different. 2 The lubricating oil compositions prepared in Comparative Examples 1 and 5, with a kinematic viscosity of 28.9 mm² at 40°C, were compared to those in Comparative Examples 1 and 5. 2 At speeds above a certain value (e.g., 1 / s), it is clear that viscosity at low temperatures cannot be reduced. Additionally, the kinematic viscosity of the lubricating oil base oil at 40°C is 18 mm⁻¹. 2The lubricating oil compositions manufactured in Comparative Examples 2-4 and 6-8, whose calculated value X was less than 0.45% / hour but whose test time was between 4 and 12 hours, all showed a change in NOACK evaporation loss per unit time (the slope of NOACK at 150°C) exceeding 0.45% / hour, indicating that the evaporation loss during use could not be reduced.

[0132] Furthermore, if the lubricating oil compositions manufactured in Examples 16-19 are compared with each other, the type and amount of PMA-based viscosity index improver were varied for each composition, but the kinematic viscosity at 40°C of all compositions was 26.0 mm. 2 The NOACK slope at 150°C is below 0.45% / hour (by mass), indicating that the composition can be designed by changing the type of PMA-based viscosity index improver according to product design without compromising evaporability or fuel-saving performance. In contrast, Comparative Example 9, which contains an OCP-based viscosity index improver (olefin copolymer), has the same HTHS viscosity at 150°C as Examples 16-19, meeting the standards specified in SAE J300, but its kinematic viscosity at 40°C is 36.5 mm. 2 The value of / s indicates that it is insufficient in terms of fuel efficiency.

[0133] It should be noted that, when comparing the lubricating oil compositions manufactured in Examples 20 to 29, the composition differs in terms of the type and amount of ashless friction modifier (organic FM agent), but the kinematic viscosity of the compositions at 40°C is 26.0 mm. 2 The slope of NOACK at 150°C is below 0.45 wt% / hour, which means that the composition can be designed by appropriately changing the type of ashless friction modifier to achieve the desired friction reduction performance without compromising volatility or fuel-saving performance.

[0134] Furthermore, compared to Examples 1-29, Examples 30-36 changed the components and their amounts by reducing the sulfur content in the compositions (it should be noted that the lubricating oil composition manufactured in Example 30 was an SAE viscosity grade 0W-16 composition, and the lubricating oil composition manufactured in Example 31 was an SAE viscosity grade 0W-20 composition). Here, the type and amount of friction modifier were changed in Examples 32-34, the amount of antioxidant was changed in Example 35, and the amount of metal-based detergent was changed in Example 36 to reduce sulfuric acid ash content compared to Example 35. However, in the lubricating oil compositions manufactured in Examples 30-36, the kinematic viscosity at 40°C was 26.0 mm. 2The slope of NOACK at 150°C is below 0.45% / hour, and the slope of NOACK at 150°C is below 0.45% / hour. Therefore, it can be seen that the composition can be designed by appropriately changing the amount of various components without compromising the volatility and fuel-saving performance.

[0135] Furthermore, in Examples 37-39, the sulfuric acid ash content was varied by changing the amount of metal-based detergent, antioxidant, and dispersant used, but the kinematic viscosity at 40°C of the lubricating oil compositions manufactured in Examples 38-39 was consistently 26.0 mm. 2 The NOACK slope at 150°C is below 0.45 wt% / hour, and the NOACK slope is below 0.45 wt% / hour. Therefore, it can be concluded that the composition can be designed by appropriately changing the types and amounts of metal-based detergents, antioxidants, and dispersants, from the viewpoint of GPF suitability and friction reduction performance, without compromising volatility and fuel-saving performance. It should also be noted that, based on Example 13, the calculated value X in Examples 40-43 is lower, and the NOACK slope at 150°C is even lower, resulting in higher performance in terms of low volatility.

[0136] These results show that by setting the kinematic viscosity of the lubricating oil base oil at 40℃ to 18 mm... 2 By setting the calculated value X to below 0.45 wt% / hour and ensuring the absence of olefin copolymers, the desired properties (such as lower viscosity) can be obtained without compromising low volatility and fuel efficiency, even with changes in the composition design. Furthermore, these results confirm that designing compositions by studying the calculated value X allows for highly accurate prediction of the lubricant composition's properties, enabling the efficient manufacture of compositions with the desired characteristics.

[0137] Industrial applicability As explained above, according to the present invention, a lubricating oil composition for internal combustion engines can be provided that simultaneously achieves high levels of low kinematic viscosity and low volatility in the low-temperature region; and a method for manufacturing a lubricating oil composition for internal combustion engines can be provided that allows for easy calculation of the composition design to achieve low volatility using specific formulas, enabling efficient manufacturing of a lubricating oil composition for internal combustion engines that simultaneously achieves high levels of low kinematic viscosity and low volatility in the low-temperature region. Such a lubricating oil composition for internal combustion engines of the present invention, which simultaneously achieves high levels of low viscosity and low volatility, is particularly useful as a lubricating oil composition for automobile engines equipped with a GPF (gasoline particulate filter), a lubricating oil composition for hybrid vehicles equipped with an internal combustion engine and an electric motor, etc.

Claims

1. A lubricating oil composition for internal combustion engines, comprising a lubricating oil base oil, wherein, The kinematic viscosity of the lubricating oil base oil at 40°C is 18.0 mm. 2 / s or less The lubricating oil composition does not contain olefin copolymers, and The estimated value X, obtained by formula (1) below, is less than 0.45 wt% / hour, representing the change in evaporation loss per unit time of the lubricating oil composition determined by the NOACK evaporation test at 150°C for 12 hours. In the formula, Y represents the estimated total evaporation loss of the lubricating oil composition as determined by the NOACK evaporation test under conditions of 150°C and 12 hours, obtained by formula (2) below. In equation (2), i represents an integer in the range of 25 to 75. A(i) represents the percentage of components, expressed as a percentage by mass, of the total amount of the lubricating oil composition, whose boiling points are determined by gas chromatography distillation and fall within the range of {(i-1)×10}℃ to (i×10)℃. B(i) represents the value obtained by the following equation (3), where B(i) is considered to be 100 if the calculated value of B(i) exceeds 100. 。 2. The lubricating oil composition for internal combustion engines according to claim 1, wherein, The estimated value X is below 0.35 mass% / hour.

3. The lubricating oil composition for internal combustion engines according to claim 1, wherein, The kinematic viscosity of the base oil for the lubricating oil at 100°C is 2.7 mm. 2 / s or higher and 4.1mm 2 / s or less.

4. The lubricating oil composition for internal combustion engines according to claim 1, wherein, The lubricating oil base oil contains at least one mineral oil-based base oil as a base oil component constituting the lubricating oil base oil.

5. The lubricating oil composition for internal combustion engines according to claim 1, further comprising a viscosity index improver, wherein the viscosity index improver is poly(meth)acrylate.

6. A method for manufacturing a lubricating oil composition for internal combustion engines containing a lubricating oil base oil, wherein, Lubricating oil compositions for internal combustion engines are manufactured by designing their composition in the following manner: The kinematic viscosity of the lubricating oil base oil at 40°C is set to 18.0 mm. 2 / s or less The lubricating oil composition is free of olefin copolymers, and The estimated value X, obtained by formula (1) below, is less than 0.45 wt% / hour, representing the change in evaporation loss per unit time of the lubricating oil composition determined by the NOACK evaporation test at 150°C for 12 hours. In the formula, Y represents the estimated total evaporation loss of the lubricating oil composition as determined by the NOACK evaporation test under conditions of 150°C and 12 hours, obtained by formula (2) below. In equation (2), i represents an integer in the range of 25 to 75. A(i) represents the percentage of components, expressed as a percentage by mass, of the total amount of the lubricating oil composition, whose boiling points are determined by gas chromatography distillation and fall within the range of {(i-1)×10}℃ to (i×10)℃. B(i) represents the value obtained by the following equation (3), where B(i) is considered to be 100 if the calculated value of B(i) exceeds 100. 。

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