JP2510088B2 - Lubricating oil composition - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a lubricating oil composition, and more particularly to a lubricating oil composition having excellent oxidative stability and hardly generating sludge.

[Problems to be Solved by Conventional Techniques and Inventions] Synthetic oils having a low aromatic content, such as mineral oils and poly α-olefin oils, which do not contain an aromatic ring in their structural units, have poor oxidation stability by themselves. However, the product responds well to antioxidants and has high oxidative stability. However, such oils have the disadvantage of low solubility in antioxidants. The antioxidant itself is deteriorated when it performs a function during use, and there is a problem that sludge is formed by the oxidation.

An important point in developing a long-life lubricating oil is to balance the level of sludge formation with the oxidation life.

Phenyl-α-naphthylamine is an excellent antioxidant, but its solubility is low, and deterioration products thereof due to oxidation and its multimers such as dimers and trimers have further drawbacks of low solubility. Therefore, in spite of its excellent antioxidation property, there is a problem that even if high oxidation stability is required, it is impossible to add a large amount to improve the oxidation stability of the lubricating oil.

British Patent No. 1,046,353 discloses a method of further alkylating a phenyl group as a means for improving the solubility of phenyl-α-naphthylamine, but an oligomer of isobutylene is mainly used as an alkylating agent. However, although this product has improved solubility in oil, it has the drawback that the solubility of the modified product is still low.

The present inventors have focused on the high antioxidant performance of phenyl-α-naphthylamine, and have conducted research to overcome the drawback that phenyl-α-naphthylamine easily forms sludge. As a result, phenyl having a specific structure can be obtained. −
It was found that when a specific amount of α-naphthylamine was added, a lubricating oil composition having extremely excellent oxidation stability and less sludge formation was obtained, and the present invention was completed.

[Means for Solving Problems] The present invention uses [I] a mineral oil having an aromatic content of 30% by weight or less and / or a synthetic oil having no aromatic ring in its structural unit as a base oil. II] General formula In the formula, R is a branched alkyl group having a carbon number of 12 or 15 derived from an oligomer of propylene. An Np-alkylphenyl-α-naphthylamine represented by the following formula is used as an essential component and 0.01% based on the total amount of the composition.
The present invention provides a lubricating oil composition containing about 5.0% by weight.

The [I] base oil referred to in the present invention is an aromatic content of 30% by weight.
The following mineral oils and / or synthetic oils containing no aromatic rings in their structural units.

As a mineral oil, the kinematic viscosity at 40 ° C is 10 to 10,000 cS
t, preferably 20 to 1,000 cSt are generally used. Usually, it is preferable to use a mineral oil obtained by subjecting a lubricating oil fraction obtained by distilling crude oil to any refining treatment such as solvent refining, sulfuric acid treatment, hydrogenation refining, and clay treatment.

The mineral oil having an aromatic content of 30% by weight, preferably 20% by weight or less is suitable. The aromatic content referred to here is a value measured by the method specified in ASTM D 2549-81.

On the other hand, synthetic oils do not contain aromatic rings in their structural units and have a kinematic viscosity of 10 to 10,000 cSt at 40 ° C.
Those generally used. Specific examples thereof include polybutene obtained by homopolymerization or copolymerization of α-olefin having 4 to 30 carbon atoms, poly-α-olefin oil such as decene-1 oligomer, butyl stearate, and methyl laurate. Diester of aliphatic dibasic acid and aliphatic monohydric alcohol represented by monoester of aliphatic monocarboxylic acid and aliphatic monohydric alcohol, di-2-ethylhexyl sebacate, dioctyl adipate, ditridecyl glutarate, etc. Trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol 2-ethylhexanoate,
Aliphatic monocarboxylic acid ester of aliphatic polyhydric alcohol represented by pentaerythritol, pelargonate, etc., Polyalkylene glycol represented by polyethylene glycol, polypropylene glycol, etc. or its monoalkyl ether, dialkyl ether, monoalkyl ester, dialkyl Examples thereof include cycloparaffins such as esters, cyclododecane, hydrindane, bicyclohexyl and tercyclohexyl, alkylcycloparaffins such as dicyclohexylbutane and dicyclohexylpropane, and mixtures thereof.

On the other hand, [II] Np-alkylphenyl-α-naphthylamine referred to in the present invention is represented by the general formula: Is a compound represented by. In the formula, R is the number of carbon atoms derived from a propylene oligomer (tetramer or pentamer)
12 or 15 branched alkyl groups are shown.

In the present invention, it is important that R is a branched alkyl group derived from an oligomer of propylene, and even if the same branched alkyl group is derived from α-olefin, the antioxidant performance of the product is It is significantly inferior to the component [II] of the invention, and those derived from olefins other than propylene, for example, oligomers such as isobutylene, are themselves unfavorable because they easily precipitate as sludge in lubricating oil.

Even when a branched alkyl group derived from an oligomer of propylene is used as R, when the number of carbon atoms is less than the range of the present invention, it itself tends to be precipitated as sludge in lubricating oil by oxidation, and Those having a carbon number exceeding the range of the present invention are not preferable because the ratio of functional groups contained in the molecule becomes small and the antioxidant ability becomes weak.

The method for synthesizing Np-alkylphenyl-α-naphthylamine, which is the [II] component of the present invention, is arbitrary and can be synthesized by a known method, but from the viewpoint of ease of synthesis,
The Friedel-Crafts alkylation reaction of an oligomer of phenyl-α-naphthylamine and propylene is preferred.
As the catalyst in this case, aluminum chloride, zinc chloride,
Metal halides such as iron chloride and acidic catalysts such as sulfuric acid, phosphoric acid, phosphorus pentoxide, boron fluoride, acid clay and activated clay are used, but the product is not colored and the reaction rate is high and the catalyst Activated clay is particularly preferred because it is easy to remove. If an activated clay / aluminum chloride mixed catalyst system having an activated clay / aluminum chloride weight ratio of 3 to 10 is used, the reaction rate can be further increased.

This Friedel-Crafts alkylation reaction is usually
It is performed as follows.

1 mol of phenyl-α-naphthylamine, 2 to 10 mol, preferably 3 to 5 mol of propylene oligomer and 50
˜200 g, preferably 80 to 150 g of activated clay is placed in a reaction vessel equipped with a temperature detector, a nitrogen blowing tube, a reflux condenser and a stirrer, and heated to 140 to 190 ° C. while stirring.
When aluminum chloride is also used as a catalyst, aluminum chloride which is 1/3 to 1/10 of the amount of white clay used thereafter is further added little by little. After that, continue the reaction at that temperature, sample at regular intervals and analyze with an analytical instrument such as gas chromatography or infrared spectroscopy, heating and stirring until the unreacted content of phenyl-α-naphthylamine shows 10% or less. Continue.

After the reaction is complete, the reaction mixture is cooled and the catalyst is removed by suction filtration. The obtained filtrate is distilled under reduced pressure, unreacted propylene oligomer is distilled off, and the residue is chromatographically purified to obtain the desired Np-alkylphenyl-α-naphthylamine as a viscous transparent liquid. To be

The compounding amount of the [II] component in the present invention is 0.01 to 5.0% by weight, preferably 0.1 to 3.0% by weight, based on the total amount of the composition.
Is. If the blending amount is less than 0.01% by weight, the effect of blending the [II] component is inferior, and if the blending amount exceeds 5.0% by weight, an effect commensurate with the added amount cannot be obtained, which is economically advantageous. They are disadvantageous and are not preferable.

Also, if necessary for the lubricating oil composition of the present invention,
Other commonly used lubricating oil additives, such as antioxidants, washing dispersants, pour point depressants, viscosity index improvers, oiliness agents, antiwear agents, extreme pressure agents, corrosion inhibitors, metal deactivators. ,
For details of these various additives that can also be added defoaming agents, emulsifiers, demulsifiers, bactericides, coloring agents, etc.,
For example, it is disclosed in the Journal of the Lubrication Society, Vol. 15, No. 6 or "Petroleum Product Additives" edited by Toshio Sakurai (Koshobo).

The lubricating oil composition of the present invention is a lubricating oil required to have oxidation stability, such as automobile engine oil, agricultural machine engine oil, diesel engine oil, marine diesel engine oil, industrial multipurpose lubricating oil, turbine oil, hydraulic oil. , Spindle oil, oil film bearing oil, refrigerator oil, gear oil, automatic transmission oil, cylinder oil, dynamo oil, no machine oil, cutting oil, metal working oil, etc.

[Examples] Next, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to these examples unless the gist is changed.

Synthesis Example 1 Phenyl-α-naphthylamine 32.9 was added to a four-necked flask.
g (0.15 mol) and specific surface area 235 m ² / g, acidity 1.5 mg-KOH
/ g of activated clay 15g is put and heated to 150 ℃ in a nitrogen stream,
101 g (0.6 mol) of propylene tetramer was sequentially added over 1 hour while stirring at high speed. After the addition was completed, high speed stirring was continued while the system was kept at 150 ° C., and the reaction was allowed to proceed for another 5 hours.

After completion of the reaction, the activated clay was filtered off, the filtrate was distilled under reduced pressure to distill off unreacted propylene tetramer, and the residue was chromatographed to obtain the desired N-colored transparent viscous liquid. 48.7 g of -p-branched dodecylphenyl-α-naphthylamine was obtained.

The viscosity of this compound is 1,612 cSt (@ 40 ° C), and the yield based on phenyl-α-naphthylamine is 84.
%Met.

Synthesis Example 2 126 g of propylene pentamer instead of propylene tetramer
Synthesis was performed in the same manner as in Synthesis Example 1 except that (0.6 mol) was used to obtain 51.6 g of the desired Np-branched pentadecylphenyl-α-naphthylamine.

The viscosity of this compound is 2,182 cSt (@ 40 ° C), and the yield based on phenyl-α-naphthylamine is 8
It was 0.2%.

Synthesis Example 3 Phenyl-α-naphthylamine 32.9 was added to a four-necked flask.
g (0.15 mol), specific surface area of 235 m ² / g, acidity of 1.5 mg-KOH / g of activated clay 15 g and aluminum chloride 3 g, and heated to 150 ° C in a nitrogen stream, while stirring at high speed, propylene 4
101 g (0.6 mol) of the monomer were sequentially added over 3 hours. After the addition was completed, high-speed stirring was continued while the system was kept at 150 ° C., and the reaction was continued for another hour.

After the reaction is completed, the activated clay and aluminum chloride are filtered off,
The filtrate was transferred to a separating funnel and washed with water. After washing with water, the unreacted propylene tetramer is distilled off under reduced pressure, and the residue is chromatographically purified to obtain the desired Np-branched dodecylphenyl-α- as a yellow transparent viscous liquid. 52.6 g of naphthylamine was obtained.

The viscosity of this compound is 1,628 cSt (@ 40 ° C), and the yield based on phenyl-α-naphthylamine is 9
It was 0.6%.

Comparative Synthesis Example 1 Phenyl-α-naphthylamine 32.9 was added to a four-necked flask.
g (0.15 mol) and 3 g of aluminum chloride were added, the mixture was heated to 140 ° C. in a nitrogen stream, and 50.5 g (0.6 mol) of propylene dimer was sequentially added over 5 hours while stirring at high speed.
After the addition was completed, the reaction product was dissolved in 100 ml of benzene,
This solution was washed with water to remove aluminum chloride, and then subjected to a rotary evaporator to remove unreacted propylene dimer and benzene as a solvent. This residue was further distilled under reduced pressure, and a fraction having a boiling point of 213 to 218 ° C./1 mHg was collected to obtain the desired Np-branched hexylphenyl-α.
31.8 g of naphthylamine were obtained.

Comparative Synthesis Example 2 Phenyl-α-naphthylamine 32.9 was added to a four-necked flask.
g (0.15 mol) and 3 g of aluminum chloride were added, the mixture was heated to 140 ° C. in a nitrogen stream, and 101 g (0.6 mol) of isobutylene trimer was sequentially added over 5 hours while stirring at high speed. After the addition was completed, the reaction product was dissolved in 100 ml of benzene, the solution was washed with water to remove aluminum chloride, and then subjected to rotary evaporation to remove the solvent benzene. The residue was further distilled under reduced pressure to remove unreacted isobutylene trimer, and the distillation residue was recrystallized with an aqueous ethanol solution to obtain 21.2 g of the desired Np-branched dodecylphenyl-α-naphthylamine in white. Crystal (melting point 116
° C).

Examples 1 to 3 and Comparative Examples 1 to 4 N which is the [II] component of the present invention obtained in Synthesis Examples 1 to 3
-P-alkylphenyl-α-naphthylamine is a refined mineral oil having an aromatic content of 7% by weight (kinetic viscosity 34.4 cSt, @ 40 ° C) and poly-α-olefin oil (decene-1-oligomer, kinematic viscosity 30.7 cSt, @ 40
C) and evaluated its solubility (Examples 1 to 1).
3). The results are shown in Table 1.

For comparison, as shown in Table 1, commercially available antioxidants such as phenyl-α-naphthylamine and N-p-branched octylphenyl-α-naphthylamine having an isobutylene dimer as an alkyl source, and comparative synthesis Also for the Np-branched hexylphenyl-α-naphthylamine obtained in Example 1 and the Np-branched dodecylphenyl-α-naphthylamine (alkyl source: isobutylene trimer) obtained in Comparative Synthesis Example 2. Similarly, the solubility of the deteriorated product by oxidation in the base oil was evaluated (Comparative Examples 1 to 4), and the results are also shown in Table 1.

In addition, phenyl-α-naphthylamine and Np-
The alteration product by the oxidation of alkylphenyl-α-naphthylamine is described by the method of RF Bridger (J.Org.Chem.Vol 33.No1.
2. (1968)) and the following method.

That is, phenyl-α-naphthylamine or N-
0.05 mol of p-alkylphenyl-α-naphthylamine is dissolved in 100 ml of acetone and cooled to 0 ° C. After 2.63 g of potassium permanganate was sequentially added to this solution over 5 hours, cooling was stopped and the mixture was allowed to stand at room temperature for 15 hours. (During this time,
Keep the system in a nitrogen atmosphere.) Filter off manganese dioxide with filter paper, remove acetone from the filtrate, dissolve the rest in 100 ml of benzene, wash with water, and distill benzene.

The product thus obtained was analyzed by infrared absorption spectrum, GPC analysis and mass spectrometry, and it was confirmed that phenyl-
α-naphthylamine or Np-alkylphenyl-
It can be seen that the main component is a modified product of α-naphthylamine by oxidation and its dimer and trimer.

Examples 4 to 6 and Comparative Examples 5 to 8 N which is the component [II] of the present invention obtained in Synthesis Examples 1 to 3.
In order to investigate the oxidation performance of the -p-alkylphenyl-α-naphthylamine, the same refined mineral oils used in Examples 1 to 3 were each added in the amounts indicated in Table 2 and the lubricating oil compositions thus obtained Then, a rotary bomb oxidation test (test temperature 150 ° C, oxygen pressure 13 kg / cm ² , copper wire catalyst) according to ASTM D2272 was performed. The oxidation performance was evaluated by the time until the oxygen pressure decreased by 1.8 kg / cm ² (Examples 4 to 6), and the results are shown in Table 2.

For comparison, the phenyl-α-naphthylamine and Np-alkylphenyl-α-naphthylamine used in Comparative Examples 1 to 4 were also evaluated for oxidation performance in the same manner (Comparative Examples 5 to 8). The results are also shown in Table 2. In Comparative Examples 5 to 7, as can be seen from the results of Comparative Examples 1 to 3 in Table 1, the amount of the compound shown in Table 2 in which a deteriorated substance due to the oxidation of the compound is deposited, that is, the risk of sludge generation. Is strong and is added in a large amount so as to cause a problem in practical use.

[Effects of the Invention] As is clear from the results of Table 1, in the N-p-alkylphenyl-α-naphthylamine which is the [II] component of the present invention, the deterioration products due to oxidation are less likely to become sludge, and therefore, the lubricating oil group. It can be seen that a large amount can be added to the oil as an antioxidant. On the other hand, commercially available antioxidants such as phenyl-α-naphthylamine (Comparative Example 1) and Np-
The branched octylphenyl-α-naphthylamine (Comparative Example 2) is significantly inferior to Examples 1 to 3 in the ability to dissolve oxidatively modified substances. Therefore, when it is used as an antioxidant, it may become sludge and cannot be added in a large amount. Even when the propylene oligomer is used as the alkyl source, as in the case of the component (II) of the present invention, Np-branched hexylphenyl-α-naphthylamine (Comparative Example 3) having a small number of carbon atoms in the alkyl group and carbon in the alkyl group. Even if the number is within the range of the present invention, even with Np-branched dodecylphenyl-α-naphthylamine (Comparative Example 4) using an isobutylene oligomer as an alkyl source, the solubility of the oxidative deterioration product is still within the range of the present invention. It can be seen that it is inferior to the [II] component.

Furthermore, from the results of Table 2, Example 4 to
Since the lubricating oil composition of No. 6 has excellent solubility of the [II] component itself and its oxidative deterioration, the addition amount of the [II] component can be freely adjusted without fear of sludge formation. Therefore, as can be seen from the results of the oxidation performance of Example 4, when high oxidation stability is required, [I
The demand can be satisfied by increasing the addition amount of the component I].

On the other hand, in the compositions of Comparative Examples 5 to 8, although the compounds themselves have the same degree of oxidation performance as the component [II] of the present invention, as is clear from the results of Comparative Examples 1 to 4, sludge is obtained. From the viewpoint of production, the amount added is largely limited, and it is impossible for the lubricating oil composition to obtain high oxidative stability like the composition of the present invention. In particular, the compositions of Comparative Examples 5 to 7 were obtained when the compound was added in such a large amount that there was a risk of sludge formation in Table 1, and the oxidation performance shown in Table 2 could not be practically obtained.

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Claims (2)

(57) [Claims] 1. A base oil comprising [I] a mineral oil having an aromatic content of 30% by weight or less and / or a synthetic oil containing no aromatic ring in its structural unit. In the formula, R is a branched alkyl group having a carbon number of 12 or 15 derived from an oligomer of propylene. An Np-alkylphenyl-α-naphthylamine represented by the following formula is used as an essential component and 0.01% based on the total amount of the composition.
A lubricating oil composition containing about 5.0% by weight. 2. The [II] Np-alkylphenyl-
α-naphthylamine has 12 or less carbon atoms in the presence of activated clay catalyst or a mixed catalyst of activated clay and aluminum chloride.
The lubricating oil composition according to claim 1, which is obtained by reacting 15 propylene oligomers with phenyl-α-naphthylamine.