Additive, method for determining the blending ratio of liquid antioxidant and solid antioxidant contained in said additive, and method for determining the amount of said additive to be added to lubricating oil

Abstract

The present invention provides an additive capable of improving transportability and handleability, a method for determining the blending ratio of a liquid antioxidant and a solid antioxidant contained in the additive, and a method for determining the amount of the additive to be added to a lubricating oil. [Solution] The additive disclosed herein contains only a liquid antioxidant as a liquid component, in which a solid antioxidant is dissolved, and the liquid antioxidant and the solid antioxidant are each either a phenolic antioxidant or an amine antioxidant.

Description

[Technical Field]

[0001] The present disclosure relates to an additive, a method for determining the blending ratio of a liquid antioxidant and a solid antioxidant contained in the additive, and a method for determining the amount of the additive to be added to a lubricating oil. [Background technology]

[0002] Patent Document 1 describes an additive that is added to improve the oxidation stability and anti-corrosion properties of lubricants used in turbine gearboxes, turbine bearings, or engines. The additive includes a base oil, an antioxidant, and a sulfur-containing additive. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2022-525421 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the additive described in Patent Document 1 requires a solvent (base oil) to dissolve the antioxidant and sulfur-containing additive, which increases the mass and volume of the additive, posing problems in transportability and handling.

[0005] In view of the above circumstances, at least one embodiment of the present disclosure aims to provide an additive that can improve transportability and handleability, a method for determining the blending ratio of a liquid antioxidant and a solid antioxidant contained in the additive, and a method for determining the amount of the additive to be added to a lubricating oil. [Means for solving the problem]

[0006] In order to achieve the above object, the additive according to the present disclosure includes only a liquid antioxidant as a liquid component, a solid antioxidant is dissolved in the liquid antioxidant, and the liquid antioxidant and the solid antioxidant are each either a phenol-based antioxidant or an amine-based antioxidant. [Effects of the Invention]

[0007] According to the additive of the present disclosure, the additive contains only a liquid antioxidant as a liquid component, and a solid antioxidant is dissolved in the liquid antioxidant, which eliminates the need for a solvent in which the solid antioxidant dissolves. This allows the mass and volume of the additive to be smaller than those of an additive that contains a solvent, thereby improving the transportability and handleability of the additive. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a flowchart of a method for determining the blending ratio of a liquid antioxidant and a solid antioxidant contained in the additive of the present disclosure. [Figure 2] 1 is a flow chart of a method for determining the dosage of an additive of the present disclosure to a lubricating oil. [Figure 3] 1 is a graph showing examples of a first relationship and a second relationship used in a method for determining an amount of an additive to be added to a lubricating oil according to the present disclosure. [Figure 4] 1 is a graph showing the masses of Additives 1 to 3. [Figure 5] 1 is a graph showing the volumes of Additives 1 to 3. DETAILED DESCRIPTION OF THE INVENTION

[0009] The additive according to the embodiment of the present disclosure will be described below with reference to the drawings. The embodiment described below shows one aspect of the present disclosure, and does not limit the disclosure. The additive according to the embodiment of the present disclosure can be arbitrarily modified within the scope of the technical idea of ​​the present disclosure.

[0010] <Configuration of the additive of the present disclosure> The additive disclosed herein is an additive to be added to a lubricating oil, and contains only a liquid antioxidant as a liquid component, with a solid antioxidant dissolved in the liquid antioxidant. The liquid antioxidant and the solid antioxidant are each either a phenolic antioxidant or an amine antioxidant. The liquid antioxidant may be a mixture of two or more liquid antioxidants, and the solid antioxidant may be a mixture of two or more solid antioxidants.

[0011] Examples of phenolic liquid antioxidants include octyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanoate (Irganox® L135 manufactured by BASF) and 2-methyl-4,6-bis[(n-octylthio)methyl]phenol (Irganox® L125 manufactured by BASF).

[0012] Examples of phenolic solid antioxidants include 2,6-di-tert-butyl-p-cresol (DBPC), 1,6-hexanediol bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (Irganox® L109 manufactured by BASF), 3-(3,5-di-tert-butyl-4-hydroxyphenyl)stearyl propionate (Irganox® L107 manufactured by BASF), 2,2′-thiodiethyl bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (Irganox® L108 manufactured by BASF), and 2,2′-thiodiethyl bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (Irganox® L109 manufactured by BASF). L115), 2,2-bis[[[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]oxy]methyl]propane-1,3-diol 1,3-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (Irganox (registered trademark) L1010 manufactured by BASF).

[0013] Examples of the amine-based liquid antioxidant include a reaction product of N-phenyl-benzeneamine and 2,4,4-trimethylpentene (Irganox® L57 manufactured by BASF) and Irganox® L67 manufactured by BASF.

[0014] Examples of the amine-based solid antioxidant include N-phenyl-1-naphthylamine, N-phenyl-1,1,3,3-tetramethylbutylnaphthalen-1-amine (Irganox (registered trademark) L06 manufactured by BASF), and P,P'-dioctyldiphenylamine.

[0015] The additive of the present disclosure contains only a liquid antioxidant as a liquid component, and a solid antioxidant is dissolved in the liquid antioxidant, which eliminates the need for a solvent in which the solid antioxidant is dissolved, and allows the volume of the additive to be smaller than that of an additive that contains a solvent, thereby improving the transportability and handleability of the additive.

[0016] If the liquid antioxidant and the solid antioxidant are both phenolic antioxidants or both amine antioxidants, the solid antioxidant can be reliably dissolved in the liquid antioxidant. However, depending on the structures of the liquid antioxidant and the solid antioxidant, even if one is a phenolic antioxidant and the other is an amine antioxidant, the solid antioxidant may dissolve in the liquid antioxidant. Therefore, all combinations of liquid antioxidants and solid antioxidants of different types are not excluded from the additives of the present disclosure.

[0017] The antioxidants include not only phenolic liquid antioxidants and solid antioxidants, and amine liquid antioxidants and solid antioxidants, but also metal antioxidants (such as zinc dialkyldiphosphate, etc.), organic sulfur antioxidants (such as dibenzyldisulfide, etc.), and nitrogen-containing compounds that are metal deactivators (such as benzotriazole, etc.). The additive of the present disclosure may be an additive in which at least one of these is dissolved in a liquid antioxidant in addition to a phenolic solid antioxidant or an amine solid antioxidant. Since such an antioxidant of other types is further dissolved in the liquid antioxidant in addition to the solid antioxidant, the concentration of the antioxidant in the additive is further concentrated.

[0018] The additive of the present disclosure may be an additive in which at least one of an antifoaming agent or a rust preventive agent is further dissolved in the liquid antioxidant. Such an additive will have at least one of antifoaming ability or rust preventive ability.

[0019] <Method for determining the mixing ratio of the liquid antioxidant and the solid antioxidant contained in the additive> Next, a method for determining the mixing ratio of the liquid antioxidant and the solid antioxidant contained in the additive of the present disclosure will be described. As shown in FIG. 1, the amounts of the liquid antioxidant and the solid antioxidant to be used are determined in advance, a predetermined amount of the liquid antioxidant and the solid antioxidant are prepared, and the solid antioxidant is dissolved in the liquid antioxidant (first dissolution step, step S1). At this time, in order to shorten the time for dissolving the solid antioxidant in the liquid antioxidant, the temperature of the liquid antioxidant may be adjusted to a temperature near the melting point of the solid antioxidant, and then the solid antioxidant may be dissolved in the liquid antioxidant. For example, the temperature of the liquid antioxidant may be adjusted to a temperature T (° C.) that satisfies (MP - 10) ≦ T < MP when the melting point of the solid antioxidant is MP (° C.), and the solid antioxidant may be dissolved in the liquid antioxidant.

[0020] The first solution in which all of the solid antioxidant has been dissolved in the liquid antioxidant in step S1 is stored at a temperature of 4°C or lower (storage step, step S2). The first solution is stored in this state preferably for 7 days or more. After step S2 is completed, the presence or absence of precipitation of the solid antioxidant in the first solution is confirmed (step S3). If precipitation of the solid antioxidant is confirmed in step S3, the process returns to step S1, and steps S1 and S2 are repeated at least once.

[0021] In the second step S1 performed after step S3, a smaller amount of solid antioxidant than that in the first step S1 is dissolved in the same amount of liquid antioxidant as that in the first step S1. Then, step S2 is performed. If precipitation of the solid antioxidant is again confirmed in the subsequent step S3, the process returns to step S1, and steps S1 and S2 are performed a third time. In the third step S1, a smaller amount of solid antioxidant than that in the second step S1 is dissolved in the same amount of liquid antioxidant as that in the second step S1. Steps S1 and S2 are repeated until precipitation of the solid antioxidant is no longer confirmed in step S3. That is, when precipitation of the solid antioxidant is no longer confirmed in step S3, the repetition of steps S1 and S2 is terminated. In each step S1, a smaller amount of solid antioxidant than the amount of solid antioxidant in the previous step S1 is dissolved in the same amount of liquid antioxidant as the amount of liquid antioxidant in the previous step S1.

[0022] If the solid antioxidant dissolved in the first solution does not precipitate in the first storage step S2, or after steps S1 and S2 are repeated at least once, a second dissolution step (step S4) is performed at least once to prepare a second solution by dissolving the solid antioxidant in the liquid antioxidant under conditions where the amount of either the liquid antioxidant or the solid antioxidant used in step S2, in which no solid antioxidant precipitated, is the same but the amount of the other is reduced. If step S4 is performed two or more times, in each step S4, the solid antioxidant is dissolved in the liquid antioxidant under conditions where the amount of either the liquid antioxidant or the solid antioxidant, which was reduced in the previous step S4, is further reduced compared to the previous step S4 and the amount of the other antioxidant is the same as in the previous step S4. The temperature of the liquid antioxidant in step S4 is not particularly limited; for example, the solid antioxidant may be dissolved in the liquid antioxidant at the above-mentioned T°C.

[0023] In step S4, whether the amount of liquid antioxidant or solid antioxidant is reduced depends on the purpose. Here, the condition for reducing the amount of solid antioxidant is defined as the first condition, and the condition for reducing the amount of liquid antioxidant is defined as the second condition. If the purpose is to reduce the volume of the additive (reduce the packaging), the second condition is adopted. If the purpose is to reduce the production cost of the additive, the second condition is adopted if the liquid antioxidant is more expensive than the solid antioxidant, and the first condition is adopted if the solid antioxidant is more expensive than the liquid antioxidant. If the purpose is to increase the antioxidant ability, the second condition is adopted if the solid antioxidant has a higher antioxidant ability than the liquid antioxidant, and the first condition is adopted if the liquid antioxidant has a higher antioxidant ability than the solid antioxidant.

[0024] If the first condition is adopted in step S4 (step S5), the process proceeds to a determination step (step S9) described later. That is, if the first condition is adopted in step S4, step S4 is performed only once. If the second condition is adopted in step S4 (step S5), it is confirmed whether all of the solid antioxidant in the second solution is dissolved in the liquid antioxidant (step S6). If all of the solid antioxidant is dissolved in the liquid antioxidant in step S6, the process returns to step S4. That is, only when the second condition is adopted in step S4, step S4 may be performed two or more times. If a portion of the solid antioxidant is not dissolved in the liquid antioxidant in step S6, the liquid phase of the second solution (from which the undissolved solid antioxidant has been removed) is stored under the same conditions as step S2 (storage step, step S7). After step S7 is completed, it is confirmed whether the solid antioxidant has precipitated from the liquid phase of the second solution (step S8). If precipitation of the solid antioxidant is confirmed in step S8, the process returns to step S4. If precipitation of the solid antioxidant is not confirmed in step S8, the process proceeds to step S9.

[0025] In step S9, the following operations are performed. When the first condition is adopted in step S4, the blending ratio of the liquid antioxidant and the solid antioxidant is determined from the amounts of the liquid antioxidant and the solid antioxidant in the second solution in step S4. When the second condition is adopted in step S4 and step S4 is performed only once, the blending ratio of the liquid antioxidant and the solid antioxidant is determined from the amounts of the liquid antioxidant and the solid antioxidant in the first solution in step S2, which was performed last. When the second condition is adopted in step S4 and step S4 is performed two or more times, the blending ratio of the liquid antioxidant and the solid antioxidant is determined from the amounts of the liquid antioxidant and the solid antioxidant in the second solution in step S4, which was performed just before the last step S4.

[0026] In this way, it is possible to produce an additive in which the solid antioxidant does not precipitate during storage, and further it is possible to reduce the volume of the additive, reduce the production cost of the additive, or increase the antioxidant ability.

[0027] <Method for determining the amount of additive to be added to lubricating oil> Next, a method for determining the amount of an additive to be added to a lubricating oil, the blending ratio of the liquid antioxidant and the solid antioxidant being determined by the above-described method, will be described. As shown in Figure 2, a first relationship is obtained (step S10), which is the relationship between the amount of liquid antioxidant and the amount of solid antioxidant added when each of the liquid antioxidant and the solid antioxidant constituting the additive is added to the lubricating oil and the amount of recovery of the RPVOT value (ASTM D 2272) of the lubricating oil. The recovery of the RPVOT value is the value obtained by subtracting the RPVOT value of the lubricating oil measured before adding the antioxidant from the RPVOT value of the lubricating oil measured after adding the antioxidant to the lubricating oil.

[0028] A specific operation of step S10 will be described by way of example. Irganox® L135 was used as the liquid antioxidant, and DBPC was used as the solid antioxidant. Different amounts of each were added to a degraded lubricating oil (FBK Turbine 32, ENEOS) (hereinafter simply referred to as "degraded oil"), and the RPVOT values ​​of the lubricating oil were measured before and after each addition. The RPVOT recovery amount was calculated from the measurement results, and the relationship between the addition amount and the RPVOT recovery amount was plotted on a graph. This graph is shown in FIG. 3. In FIG. 3, the regression curves of the plots for the liquid antioxidant and the solid antioxidant are drawn with dashed lines. These dashed curves represent the first relationships for the liquid antioxidant and the solid antioxidant, respectively.

[0029] 2, based on the first relationship obtained by the above-described operation, a second relationship is obtained, which is the relationship between the amount of additive added and the recovery amount of the RPVOT value of the degraded oil when the additive is added to the degraded oil, from the blending ratio of the liquid antioxidant and the solid antioxidant in the additive (step S11). The specific operation of step S11 will be described below by way of example, using a mixture of Irganox (registered trademark) L135 and DBPC in a mass ratio of 2:1 as the additive to be added to the degraded oil. For example, the RPVOT recovery time when adding an additive to a degraded oil at a 1.5 wt% additive amount is 125 min, which is the sum of 45 min, the RPVOT recovery time when adding Irganox® L135 to a degraded oil at a 1.0 wt% additive amount, and 80 min, the RPVOT recovery time when adding DBPC to a degraded oil at a 0.5 wt% additive amount, based on the first relationship in Figure 3, since the mass ratio of Irganox® L135 to DBPC in the additive is 2:1. In this way, the RPVOT recovery time for different additive amounts can be obtained from the first relationship, and a solid curve can be drawn in Figure 3. This solid curve is the second relationship.

[0030] As shown in Figure 2, based on the second relationship obtained by the above-mentioned operation, it is possible to determine the amount of additive to be added that will achieve the recovery amount of the RPVOT value required for the lubricating oil (step S12). To explain the operation of step S12 by way of example, as shown in Figure 3, if it is desired to achieve the recovery amount of the RPVOT value of 50 min by adding the above-mentioned additive to degraded oil, the value on the horizontal axis when the value on the vertical axis of the solid curve representing the second relationship is 50 min is 0.3 wt%, so the amount of additive to be added to the degraded oil will be approximately 0.3 wt%.

[0031] In this way, an appropriate amount of additive can be added to deteriorated oil, thereby restoring the RPVOT value of the lubricating oil to an appropriate value. [Example]

[0032] <Verification of the mass and volume reduction effect of the additive of the present disclosure> The inventors of the present disclosure confirmed that when 1 g of DBPC as a solid antioxidant was dissolved in 1 g of Irganox® L135 as a liquid antioxidant at room temperature, all of the DBPC dissolved. The inventors of the present disclosure also confirmed that when 1 g of DBPC was dissolved in 2 g of Irganox® L135 at room temperature, all of the DBPC dissolved. This confirmed that an additive in which DBPC is dissolved in Irganox® L135 can have a DBPC concentration of up to 50 wt%. Furthermore, the inventors of the present disclosure measured the mass and volume after dissolving 270 g of DBPC in 540 g of Irganox® L135 at 60°C. Based on these measurement results, they calculated the mass and volume of Additive 1, which would provide a 2:1 mass ratio of Irganox® L135 to DBPC and a total mass of 1.0 kmol.

[0033] The inventors of the present disclosure confirmed that up to 20 g of DBPC can be dissolved in 100 g of base oil (Diana Fresia (registered trademark), Idemitsu Kosan Co., Ltd.) at room temperature, and that up to 5 g of DBPC can be dissolved in 100 g of the same base oil at 0°C. Based on these results, the inventors of the present disclosure calculated the mass and volume of Additives 2 and 3, in which 1.0 kmol of DBPC was dissolved in the same base oil at room temperature and 0°C, respectively. The masses and volumes of Additives 1 to 3 are shown in Figures 4 and 5, respectively. It was confirmed that Additive 1, which does not use base oil, had a significantly lower mass and volume than Additives 2 and 3, which do use base oil. From these results, it can be said that the additives of the present disclosure can be made smaller in mass and volume than additives in which an antioxidant is dissolved in base oil, and therefore have excellent transportability and handleability.

[0034] <Verification of precipitation of solid antioxidant in the additive of the present disclosure> The inventors of the present disclosure prepared Additives 4 to 8 shown in Table 1 below, and stored them at low temperatures for the storage periods shown in Table 1, respectively, to confirm whether or not DBPC precipitated.

[0035] [Table 1]

[0036] No DBPC precipitation occurred during low-temperature storage for Additives 4, 5, 7, and 8. Additive 6 solidified during low-temperature storage because the storage temperature was below the melting point of Irganox® L135, resulting in DBPC precipitation. From these results, it can be said that once DBPC is dissolved in Irganox® L135, no DBPC precipitation will occur unless it is cooled to below the melting point of the latter and solidifies.

[0037] The contents described in each of the above embodiments can be understood, for example, as follows.

[0038] [1] The additive according to one embodiment is The liquid component contains only a liquid antioxidant, and a solid antioxidant is dissolved in the liquid antioxidant; The liquid antioxidant and the solid antioxidant are each either a phenolic antioxidant or an amine antioxidant.

[0039] According to the additive of the present disclosure, the additive contains only a liquid antioxidant as a liquid component, and a solid antioxidant is dissolved in the liquid antioxidant, which eliminates the need for a solvent in which the solid antioxidant dissolves. This allows the mass and volume of the additive to be smaller than those of an additive that contains a solvent, thereby improving the transportability and handleability of the additive.

[0040] [2] The additive according to another embodiment is the additive according to [1], Both the liquid antioxidant and the solid antioxidant are phenolic antioxidants.

[0041] According to this configuration, since both the liquid antioxidant and the solid antioxidant are phenolic antioxidants, the solid antioxidant can be reliably dissolved in the liquid antioxidant.

[0042] [3] The additive according to yet another embodiment is the additive according to [1], Both the liquid antioxidant and the solid antioxidant are amine-based antioxidants.

[0043] According to this configuration, since both the liquid antioxidant and the solid antioxidant are amine-based antioxidants, the solid antioxidant can be reliably dissolved in the liquid antioxidant.

[0044] [4] An additive according to yet another embodiment is any one of the additives [1] to [3], At least one of a metal-based antioxidant, an organic sulfur-based antioxidant, and a nitrogen-containing compound is dissolved in the liquid antioxidant.

[0045] According to this configuration, since other antioxidants are dissolved in the liquid antioxidant in addition to the solid antioxidant, the concentration of the antioxidant in the additive can be further concentrated.

[0046] [5] An additive according to yet another embodiment is any one of the additives [1] to [4], At least one of an antifoaming agent and an anticorrosive agent is dissolved in the liquid antioxidant.

[0047] According to this configuration, the additive can be endowed with at least one of an anti-foaming ability and an anti-rust ability.

[0048] [6] A method for determining the blending ratio of the liquid antioxidant and the solid antioxidant contained in the additive according to one embodiment includes the steps of: A method for determining a blending ratio of a liquid antioxidant and a solid antioxidant contained in any one of the additives [1] to [5], comprising: a first dissolving step of dissolving a predetermined amount of the solid antioxidant in a predetermined amount of the liquid antioxidant; a storage step of storing the first solution prepared in the first dissolving step at a temperature of 4°C or less; Including, when a part of the solid antioxidant dissolved in the first solution precipitates in the storing step, the first dissolving step and the storing step are repeated at least once, and in the first dissolving step that is repeated at least once, an amount of the solid antioxidant that is smaller than the amount of the solid antioxidant in the first dissolving step that was performed immediately before is dissolved in an amount of the liquid antioxidant that is the same as the amount of the liquid antioxidant in the first dissolving step that was performed immediately before; and when the solid antioxidant dissolved in the first solution no longer precipitates in the storing step that is repeated at least once, the first dissolving step and the storing step that are repeated at least once are terminated. If the solid antioxidant dissolved in the first solution does not precipitate in the storing step that is performed initially, or after the first dissolving step and the storing step are repeated at least once, a second dissolving step is performed at least once to prepare a second solution by dissolving the solid antioxidant in the liquid antioxidant under either a first condition in which the amount of the liquid antioxidant used in the storing step in which no precipitation of the solid antioxidant occurred is the same but the amount of the solid antioxidant is reduced, or a second condition in which the amount of the solid antioxidant used in the storing step in which no precipitation of the solid antioxidant occurred is the same but the amount of the liquid antioxidant is reduced, When the second dissolving step is performed two or more times, in each of the second dissolving steps, the amount of the liquid antioxidant or the solid antioxidant, whichever is smaller in the second dissolving step performed immediately before, is made even smaller than in the second dissolving step performed immediately before, and the amount of the other antioxidant is made the same as in the second dissolving step performed immediately before, and when the first condition is adopted, the second dissolving step is performed only once, and when the second condition is adopted, the second dissolving step, which is performed at least once, is terminated if the solid antioxidant dissolved in the second solution precipitates in the second dissolving step, which is performed at least once. When the first condition is adopted in the second dissolving step, the blending ratio of the liquid antioxidant and the solid antioxidant is determined from the amounts of the liquid antioxidant and the solid antioxidant in the second solution in the second dissolving step. When the second condition is adopted in the second dissolving step and a portion of the solid antioxidant does not dissolve, the liquid phase of the second solution is stored at a temperature of 4°C or less, and after confirming that there is no precipitation of the solid antioxidant due to this storage, if the second dissolving step is performed only once, the blending ratio of the liquid antioxidant and the solid antioxidant is determined from the amounts of the liquid antioxidant and the solid antioxidant in the first solution in the last storage step. If the second dissolving step is performed two or more times, the blending ratio of the liquid antioxidant and the solid antioxidant is determined from the amounts of the liquid antioxidant and the solid antioxidant in the second solution in the second dissolving step that was performed just before the last second dissolving step.

[0049] According to the method of the present disclosure, it is possible to produce an additive in which the solid antioxidant does not precipitate during storage, and further to reduce the mass and volume of the additive, reduce the production cost of the additive, or increase the antioxidant ability.

[0050] [7] A method for determining the amount of additive to be added to a lubricating oil according to one embodiment includes: A method for determining the amount of the additive to be added to a lubricating oil, the amount being determined by the method of [6], obtaining a first relationship which is a relationship between the amount of recovery of the RPVOT value of the lubricating oil and the amount of addition of the liquid antioxidant and the solid antioxidant when each of the liquid antioxidant and the solid antioxidant is added to the lubricating oil; A step of obtaining a second relationship, which is a relationship between the amount of the additive added to the lubricating oil and the recovery amount of the RPVOT value of the lubricating oil, from the blending ratio of the additive based on the first relationship; determining, based on the second relationship, the amount of the additive that will achieve the recovery amount of the RPVOT value required for the lubricating oil; Includes:

[0051] According to the method of the present disclosure, an appropriate amount of additive can be added to deteriorated lubricating oil, thereby restoring the RPVOT value of the lubricating oil to an appropriate value.

Claims

1. The liquid component contains only a liquid antioxidant, and a solid antioxidant is dissolved in the liquid antioxidant, The additive wherein the liquid antioxidant and the solid antioxidant are each either a phenolic antioxidant or an amine antioxidant.

2. 2. The additive of claim 1, wherein the liquid antioxidant and the solid antioxidant are both phenolic antioxidants.

3. 2. The additive of claim 1, wherein the liquid antioxidant and the solid antioxidant are both amine-based antioxidants.

4. The additive according to any one of claims 1 to 3, wherein at least one of a metal-based antioxidant, an organic sulfur-based antioxidant, or a nitrogen-containing compound is dissolved in the liquid antioxidant.

5. The additive according to any one of claims 1 to 3, wherein at least one of an antifoaming agent and an antirust agent is dissolved in the liquid antioxidant.

6. A method for determining a blending ratio of a liquid antioxidant and a solid antioxidant contained in the additive according to any one of claims 1 to 3, comprising: a first dissolving step of dissolving a predetermined amount of the solid antioxidant in a predetermined amount of the liquid antioxidant; a storage step of storing the first solution prepared in the first dissolving step at a temperature of 4°C or less; Including, when a part of the solid antioxidant dissolved in the first solution precipitates in the storing step, the first dissolving step and the storing step are repeated at least once, and in the first dissolving step that is repeated at least once, an amount of the solid antioxidant that is smaller than the amount of the solid antioxidant in the first dissolving step that was performed immediately before is dissolved in an amount of the liquid antioxidant that is the same as the amount of the liquid antioxidant in the first dissolving step that was performed immediately before; and when the solid antioxidant dissolved in the first solution no longer precipitates in the storing step that is repeated at least once, the first dissolving step and the storing step that are repeated at least once are terminated. If the solid antioxidant dissolved in the first solution does not precipitate in the first storing step, or after the first dissolving step and the storing step are repeated at least once, a second dissolving step is performed at least once to prepare a second solution by dissolving the solid antioxidant in the liquid antioxidant under either a first condition in which the amount of the liquid antioxidant used in the storing step in which no precipitation of the solid antioxidant occurred is the same but the amount of the solid antioxidant is reduced, or a second condition in which the amount of the solid antioxidant used in the storing step in which no precipitation of the solid antioxidant occurred is the same but the amount of the liquid antioxidant is reduced, When the second dissolving step is performed two or more times, in each of the second dissolving steps, the amount of the liquid antioxidant or the solid antioxidant, whichever was less in the second dissolving step performed immediately before, is made even less than in the second dissolving step performed immediately before, and the amount of the other antioxidant is made the same as in the second dissolving step performed immediately before, and when the first condition is adopted, the second dissolving step is performed only once, and when the second condition is adopted, the second dissolving step, which is performed at least once, is terminated if the solid antioxidant dissolved in the second solution precipitates in the second dissolving step, which is performed at least once. When the first condition is adopted in the second dissolving step, a blending ratio of the liquid antioxidant and the solid antioxidant is determined from the amounts of the liquid antioxidant and the solid antioxidant in the second solution in the second dissolving step. When the second condition is adopted in the second dissolving step and a part of the solid antioxidant does not dissolve, the liquid phase of the second solution is stored at a temperature of 4° C. or less, and after confirming that the solid antioxidant does not precipitate due to the storage, if the second dissolving step is performed only once, a blending ratio of the liquid antioxidant and the solid antioxidant is determined from the amounts of the liquid antioxidant and the solid antioxidant in the first solution in the last storage step. If the second dissolving step is performed two or more times, a blending ratio of the liquid antioxidant and the solid antioxidant is determined from the amounts of the liquid antioxidant and the solid antioxidant in the second solution in the second dissolving step that is performed just before the last second dissolving step.

7. A method for determining the amount of the additive to be added to a lubricating oil having the blending ratio determined by the method of claim 6, comprising: obtaining a first relationship which is a relationship between the amount of recovery of the RPVOT value of the lubricating oil and the amount of addition of the liquid antioxidant and the solid antioxidant when each of the liquid antioxidant and the solid antioxidant is added to the lubricating oil; obtaining a second relationship, which is a relationship between the amount of the additive added to the lubricating oil and the recovery amount of the RPVOT value of the lubricating oil, from the blending ratio of the additive based on the first relationship; determining, based on the second relationship, the amount of the additive that will achieve the recovery amount of the RPVOT value required for the lubricating oil; A method comprising:

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