U.S. patent application number 14/360721 was filed with the patent office on 2015-10-22 for friction and wear reducing agent for lubricating oil and lubricating oil composition containing same.
The applicant listed for this patent is ADEKA CORPORATION. Invention is credited to Masahiro TAKATA, Kenji YAMAMOTO.
Application Number | 20150299604 14/360721 |
Document ID | / |
Family ID | 48612587 |
Filed Date | 2015-10-22 |
United States Patent
Application |
20150299604 |
Kind Code |
A1 |
TAKATA; Masahiro ; et
al. |
October 22, 2015 |
FRICTION AND WEAR REDUCING AGENT FOR LUBRICATING OIL AND
LUBRICATING OIL COMPOSITION CONTAINING SAME
Abstract
The purpose of the present invention is to provide an additive
for lubricating oil, which does not substantially contain metal
elements or the like and is safe but which demonstrates extreme
pressure performance equivalent to conventional extreme pressure
agents each containing a metal element when used in lubricating
applications. In order to achieve the above-mentioned purpose, the
present invention provides a friction and wear reducing agent for
lubricating oil consisting of a copolymer (A) comprising an alkyl
acrylate (a) represented by the following general formula (1) and a
hydroxyalkyl acrylate (b) represented by the following general
formula (2) as essential constituent monomers, wherein the
constitutive ratio of (a) to (b) is 50/50 to 90/10 (molar ratio)
and the weight average molecular weight thereof is 2,000 to less
than 40,000. ##STR00001## (in the above formula, R' represents an
alkyl group having 10 to 18 carbon atoms) ##STR00002## (in the
above formula, R.sup.2 represents an alkylene group having 2 to 4
carbon atoms)
Inventors: |
TAKATA; Masahiro; (Tokyo,
JP) ; YAMAMOTO; Kenji; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ADEKA CORPORATION |
Tokyo |
|
JP |
|
|
Family ID: |
48612587 |
Appl. No.: |
14/360721 |
Filed: |
December 12, 2012 |
PCT Filed: |
December 12, 2012 |
PCT NO: |
PCT/JP2012/082225 |
371 Date: |
May 27, 2014 |
Current U.S.
Class: |
508/500 ;
508/503 |
Current CPC
Class: |
C10M 2217/022 20130101;
C10M 145/14 20130101; C10N 2030/06 20130101; C10M 2205/0285
20130101; C10M 149/04 20130101; C10N 2040/16 20130101; C10M
2211/022 20130101; C10N 2040/02 20130101; C10N 2040/30 20130101;
C10M 2223/041 20130101; C10M 2203/1006 20130101; C10M 2207/289
20130101; C10N 2020/02 20130101; C08F 220/18 20130101; C10N 2040/20
20130101; C10M 2209/084 20130101; C10N 2040/25 20130101; C10N
2020/04 20130101; C10N 2040/08 20130101; C10N 2040/12 20130101;
C08F 220/1811 20200201; C08F 220/20 20130101; C08F 220/1811
20200201; C08F 220/20 20130101 |
International
Class: |
C10M 149/04 20060101
C10M149/04 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 13, 2011 |
JP |
2011-272558 |
Claims
1. A friction and wear reducing agent for lubricating oil
consisting of a copolymer (A) comprising an alkyl acrylate (a)
represented by the following general formula (1) and a hydroxyalkyl
acrylate (b) represented by the following general formula (2) as
essential constituent monomers, wherein the constitutive ratio of
(a) to (b) is 50/50 to 90/10 (molar ratio) and the weight average
molecular weight thereof is 2,000 to less than 40,000. ##STR00007##
(in the above formula, R.sup.1 represents an alkyl group having 10
to 18 carbon atoms) ##STR00008## (in the above formula, R.sup.2
represents an alkylene group having 2 to 4 carbon atoms)
2. The friction and wear reducing agent for lubricating oil
according to claim 1, wherein the copolymer (A) is a copolymer
consisting of an alkyl acrylate (a) and a hydroxyalkyl acrylate
(b).
3. The friction and wear reducing agent for lubricating oil
according to claim 1, wherein R.sup.1 of the alkyl acrylate (a) is
an alkyl group having 10 to 14 carbon atoms.
4. A lubricating oil composition comprising a base oil and the
friction and wear reducing agent for lubricating oil according to
claim 1, wherein the friction and wear reducing agent for
lubricating oil is contained in an amount of 0.1 to 50% by weight
with respect to the total amount of the lubricating oil
composition.
5. A lubricating oil composition comprising a base oil and the
friction and wear reducing agent for lubricating oil according to
claim 3, wherein the friction and wear reducing agent for
lubricating oil is contained in an amount of 0.1 to 50% by weight
with respect to the total amount of the lubricating oil
composition.
6. The friction and wear reducing agent for lubricating oil
according to claim 2, wherein R.sup.1 of the alkyl acrylate (a) is
an alkyl group having 10 to 14 carbon atoms.
7. A lubricating oil composition comprising a base oil and the
friction and wear reducing agent for lubricating oil according to
claim 2, wherein the friction and wear reducing agent for
lubricating oil is contained in an amount of 0.1 to 50% by weight
with respect to the total amount of the lubricating oil
composition.
8. A lubricating oil composition comprising a base oil and the
friction and wear reducing agent for lubricating oil according to
claim 6, wherein the friction and wear reducing agent for
lubricating oil is contained in an amount of 0.1 to 50% by weight
with respect to the total amount of the lubricating oil
composition.
Description
TECHNICAL FIELD
[0001] The present invention relates to an additive for lubricating
oil having both extreme pressure performance and a friction
reducing effect. More specifically, the present invention relates
to an additive for lubricating oil which does not substantially
contain metal elements or elements such as phosphorous or sulfur
but which demonstrates performance equivalent to that of
conventional extreme pressure agents containing metal elements or
elements such as phosphorous or sulfur and also has both friction
and wear reducing effects.
BACKGROUND ART
[0002] There are various lubricating oil applications such as
metalworking oil, engine oil, drive system oil or hydraulic oil. In
recent years, machinery has come to demonstrate higher levels of
performance and larger size and lubricating oil has decreased in
viscosity in order to realize reduced fuel consumption. Due to the
effects of these changes, there are an increasing number of cases
in which contact surfaces requiring lubricating oil are being
subjected to higher pressures than ever before, thereby resulting
in the unwanted outcome of an increase in problems stemming from
excessive wear of those contact surfaces. An extreme pressure agent
is commonly used to prevent such wear (see, for example, Patent
Publications 1 to 3).
[0003] Patent Publication 1 describes examples of extreme pressure
agents for lubricating oil that include sulfides, sulfoxides,
sulfones, thiosulfides, thiocarbonates, dithiocarbonates,
alkylthiocarbamoyls, fats and oils, sulfurized oils, sulfurized
olefins, phosphate esters, phosphite esters, phosphate ester amine
salts, phosphite ester amine salts, chlorinated hydrocarbons,
chlorinated oils, zinc dithiophosphate and thiocarbamates.
[0004] Patent Publication 2 describes examples of extreme pressure
agents of lubricating oils that include lead naphthenate,
sulfurized fatty acid esters, sulfurized sperm oil, sulfurized
terpene, dibenzyl disulfide, chlorinated paraffins, chloronaphtha
xanthate, tricresyl phosphate, tributyl phosphate, tricresyl
phosphite, n-butyl di-n-octyl phosphinate, di-n-butyl dihexyl
phosphonate, di-n-butyl phenyl phosphonate, dibutyl
phosphoroamidate and amine dibutyl phosphate.
[0005] Patent Publication 3 describes examples of extreme pressure
agents of lubricating oils that include sulfurized oils, olefin
polysulfides, dibenzyl sulfide, monooctyl phosphate, tributyl
phosphate, triphenyl phosphite, tributyl phosphite, thiophosphate
esters, thiophosphate metal salts, thiocarbamate metal salts and
acidic phosphate ester metal salts.
[0006] However, nearly all of these known extreme pressure agents
contain elements such as sulfur, phosphorous, lead, zinc or
chlorine as indicated above. Although these elements fulfill an
important role as extreme pressure agents, there are also cases in
which they cause corrosion of lubricated surfaces, cases in which
they have a detrimental effect on human health, and cases in which
they have a detrimental effect on the environment when disposing of
lubricating oil. In consideration of an increased awareness of
environmental issues and physical safety in recent years, the use
of compounds containing these elements is being avoided, while
there is also a strong desire to demonstrate effects using
compounds composed of the three elements of carbon, hydrogen and
oxygen. On the other hand, although compounds not containing metal
elements such as fats and oils (see Patent Publication 1) or fatty
acid esters are also known to demonstrate performance as extreme
pressure agents, the level of performance of these compounds as
extreme pressure agents is low, thereby preventing them from being
used under severe conditions. On the basis thereof, there is a
desire for a highly safe extreme pressure agent that demonstrates
performance equal to that of known extreme pressure agents
containing metal elements and the like without containing the
above-mentioned metal elements and the like.
[0007] With the foregoing in view, the applicant of the present
application filed a patent application for an invention of an
extreme pressure agent not containing metal elements on Aug. 17,
2010 (Patent Publication 4). The safety of the extreme pressure
agent according to this invention is high, it demonstrates a high
level of extreme pressure performance in a high load environment,
and it can be preferably used for applications in which extreme
pressure agents are used under high loads such as in metalworking
oil or gear oil. However, in applications such as engine oil or
bearing oil in which extreme pressure agents are not subjected to
extremely high loads, rather than extreme pressure performance
capable of withstanding high loads, extreme pressure performance
capable of withstanding low loads for a long period of time is
required, while also preferably having a friction reducing effect.
Although the extreme pressure agent described in Patent Publication
4 has extreme pressure performance capable of withstanding high
loads as well as extreme pressure performance capable of
withstanding low loads over a long period of time, it does not
demonstrate a friction and wear reducing effect, thus resulting in
a need on the market for a safe additive, which in addition to
demonstrating extreme pressure performance capable of withstanding
low loads over a long period of time, simultaneously demonstrates
friction and wear reducing effects.
CONVENTIONAL ART REFERENCES
Patent Publications
[0008] Patent Publication 1: Japanese Patent Application Laid-open
No. H1-287196
[0009] Patent Publication 2: Japanese Patent Application Laid-open
No. 2002-012881
[0010] Patent Publication 3: Japanese Patent Application Laid-open
No. 2005-325241
[0011] Patent Publication 4: Japanese Patent Application No.
2010-182256
SUMMERY OF THE INVENTION
[0012] Thus, a purpose of the present invention is to provide a
friction and wear reducing agent as a lubricating oil additive,
which does not substantially contain metal element or the like and
is safe but which demonstrates extreme pressure performance
equivalent to those of conventional extreme pressure agents each
containing a metal element when used in lubricating
application.
[0013] Therefore, as a result of conducting extensive studies, the
inventors of the present invention found an additive that has
extreme pressure properties and demonstrates friction and wear
reducing effects without containing metal elements and the like, to
complete the present invention. Namely, the present invention is a
friction and wear reducing agent for lubricating oil consisting of
a copolymer (A)comprising an alkyl acrylate (a) represented by the
following general formula (1) and a hydroxyalkyl acrylate (b)
represented by the following general formula (2) as essential
constituent monomers, wherein the constitutive ratio of (a) to (b)
is 50/50 to 90/10 (molar ratio) and the weight average molecular
weight thereof is 2,000 to less than 40,000.
##STR00003##
[0014] (In the above formula, R.sup.1represents an alkyl group
having 10 to 18 carbon atoms.)
##STR00004##
[0015] (In the above formula, R.sup.2 represents an alkylene group
having 2 to 4 carbon atoms.)
[0016] The effects of the present invention are to provide an
additive which does not substantially contain metal elements or the
like and is safe, more specifically, to provide a friction and wear
reducing agent for lubricating oil consisting of the three elements
of carbon, hydrogen and oxygen, which demonstrates extreme pressure
performance equivalent to those of conventional extreme pressure
agents each containing a metal element and also demonstrates a
friction and wear reducing effect when used in lubricating
applications.
DETAILED DESCRIPTION OF THE INVENTION
[0017] The alkyl acrylate (a) used in the present invention is an
alkyl acrylate having an alkyl group with 10 to 18 carbon atoms,
and is represented by the following general formula (1):
##STR00005##
[0018] (in the above formula, R.sup.1 represents an alkyl group
having 10 to 18 carbon atoms).
[0019] Examples of R.sup.1 in the above-mentioned general formula
(1) include linear alkyl groups such as a decyl group, undecyl
group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl
group, hexadecyl group, heptadecyl group or octadecyl group; and
branched alkyl groups such as a branched decyl group, branched
undecyl group, branched dodecyl group, branched tridecyl group,
branched tetradecyl group, branched pentadecyl group, branched
hexadecyl group, branched heptadecyl group or branched octadecyl
group. Among these, from the viewpoint of the balance between
solubility in lubricating oil and extreme pressure properties,
alkyl groups having 10 to 16 carbon atoms are preferable, alkyl
groups having 10 to 14 carbon atoms are more preferable, and linear
alkyl groups having 10 to 14 carbon atoms are even more
preferable.
[0020] The hydroxyalkyl acrylate (b) used in the present invention
is a hydroxyalkyl acrylate having an alkylene group with 2 to 4
carbon atoms, and is represented by the following general formula
(2):
##STR00006##
[0021] (in the above formula, R.sup.2 represents an alkylene group
having 2 to 4 carbon atoms).
[0022] Examples of R.sup.2 in the above-mentioned general formula
(2) include an ethylene group, propylene group, butylene group,
methyl ethylene group, methyl propylene group and dimethyl ethylene
group. Among these, alkylene groups having 2 to 3 carbon atoms are
preferable since they can be produced inexpensively, and an
ethylene group is more preferable.
[0023] The copolymer (A) can be obtained by copolymerizing the
above-mentioned monomers (a) and (b). There are no particular
limitations on the polymerized form of the copolymer (A), and it
may be in any of the forms of a block copolymer, random copolymer
or block/random copolymer. Among these, a random copolymer is
preferable due to the ease of the polymerization reaction. Since
the reaction ratio of monomers (a) and (b) has a considerable
effect on extreme pressure performance of the resulting copolymer
as well as solubility in base oil, the reaction ratio between (a)
and (b), i.e. (a)/(b) must range from 50/50 to 90/10 (molar ratio),
preferably 55/45 to 85/15 (molar ratio), and more preferably 60/40
to 80/20 (molar ratio). If the ratio of the monomer (a) is larger
than (a)/(b)=90/10 (molar ratio), favorable extreme pressure
performance cannot be obtained, while if the ratio of the monomer
(b) is larger than (a)/(b)=50/50 (molar ratio), solubility in base
oil becomes poor, thereby resulting in problems such as
precipitation and clouding.
[0024] Although the copolymer (A) obtained by copolymerizing the
monomers (a) and (b) is required to have a weight average molecular
weight of 2,000 to less than 40,000, when considering the balance
between extreme pressure effect and friction and wear reducing
effects, the weight average molecular weight thereof is preferably
5,000 to 30,000 and more preferably 10,000 to 25,000. If the weight
average molecular weight is less than 2,000, there are cases in
which favorable extreme pressure performance and friction and wear
reducing effects cannot be obtained or production may become
difficult, while if the weight average molecular weight is 40,000
or higher, there are cases in which favorable friction and wear
reducing effects cannot be obtained or the resulting friction and
wear reducing agent may be not be soluble in base oil. In addition,
weight average molecular weight is measured by GPC and is
determined in terms of styrene.
[0025] There are no particular limitations on the method used to
synthesize the friction and wear reducing agent for lubricating oil
of the present invention, and it may be synthesized by any method
provided it is a known method. Although examples of such methods
include emulsification polymerization, suspension polymerization
and solution polymerization, since the friction and wear reducing
agent for lubricating oil of the present invention is used by
adding to a base oil such as a mineral oil or synthetic oil,
solution polymerization using as a solvent an organic solvent that
dissolves in the base oil is preferable to a polymerization method
that uses water as a solvent in the manner of emulsification
polymerization or suspension polymerization. Although a step is
required for removing water following completion of synthesis if
emulsification polymerization or suspension polymerization is used
for synthesis, in the case of solution polymerization, a product of
the present invention can be added directly to a base oil while
still containing solvent without having to remove the solvent used.
In addition, in the case of solution polymerization, a finished
product may be obtained by further adding solvent to the system
following completion of polymerization, or a finished product may
be obtained after removing all or a portion of the solvent.
[0026] A specific example of a method for carrying out solution
polymerization comprises charging the monomer (a) and the monomer
(b) in a solvent into a reactor such that the total monomers
account for 5 to 80%, by weight, followed by raising the
temperature to about 80.degree. C. to 120.degree. C., adding an
initiator in an amount equal to 0.1 to 10 mol % based on the total
amount of monomers either all at once or in several batches,
stirring for about 1 hour to 20 hours, and reacting such that the
weight average molecular weight becomes 2,000 to less than 40,000.
Alternatively, the monomers and solvent may be charged all at once
followed by raising the temperature to about 80.degree. C. to
120.degree. C., stirring for about 1 hour to 20 hours, and reacting
such that the weight average molecular weight becomes 2,000 to less
than 40,000.
[0027] Examples of solvents that can be used include alcohols such
as methanol, ethanol, propanol or butanol; hydrocarbons such as
benzene, toluene, xylene or hexane; esters such as ethyl acetate,
butyl acetate or isobutyl acetate; ketones such as acetone, methyl
ethyl ketone or methyl isobutyl ketone; ethers such as
methoxybutanol, ethoxybutanol, ethylene glycol monomethyl ether,
ethylene glycol dimethyl ether, ethylene glycol monobutyl ether,
propylene glycol monomethyl ether, propylene glycol dimethyl ether,
propylene glycol monobutyl ether or dioxane; mineral oils such as
paraffin-based mineral oil, naphthene-based mineral oil or refined
mineral oils obtained by refining these oils by hydrorefining,
solvent deasphalting, solvent extraction, solvent dewaxing,
hydrodewaxing, catalytic dewaxing, hydrocracking, alkali
distillation, sulfuric acid treatment or clay treatment; synthetic
oils such as poly-.alpha.-olefins, ethylene-.alpha.-olefin
copolymers, polybutenes, alkyl benzenes, alkyl naphthalenes,
polyphenyl ethers, alkyl-substituted diphenyl ethers, polyol
esters, dibasic acid esters, hindered esters, monoesters and gas to
liquids (GTL), and mixtures thereof.
[0028] Examples of initiators that can be used include azo-based
initiators such as 2,2'-azobis(2-methylpropionitrile),
2,2'-azobis(2-amidinopropane)dihydrochloride,
2,2'-azobis-(N,N-dimethyleneisobutyramidine)dihydrochloride or
1,1'-azobis(cyclohexyl-l-carbonitrile), hydrogen peroxide and
organic peroxides such as benzoyl peroxide, t-butyl hydroperoxide,
cumene hydroperoxide, methyl ethyl ketone peroxide or perbenzoic
acid, persulfates such as sodium persulfate, potassium persulfate
or ammonium persulfate, redox initiators such as hydrogen
peroxide-Fe.sup.3+, and other known radical initiators.
[0029] Although the weight average molecular weight of the friction
and wear reducing agent for lubricating oil of the present
invention is required to be 2,000 to less than 40,000, since it is
difficult to lower molecular weight in a polymerization reaction,
the molecular weight easily reaches 40,000 or higher when carrying
out an ordinary polymerization reaction. Although it is possible to
produce a polymer of a prescribed molecular weight by controlling
the reaction temperature and amount of initiator, a method
comprising a step of polymerization using a solvent having a high
chain transfer constant, a method comprising a step of
polymerization adding a chain transfer agent, or a method
comprising a step of polymerization combining the use of a solvent
having a high chain transfer constant and a chain transfer agent is
preferable since such methods facilitate production. The use of
these methods enables a polymer having low molecular weight to be
easily produced.
[0030] Examples of solvents having a high chain transfer constant
include ethanol, propanol, isopropanol, butanol, isobutanol,
toluene, ethyl benzene, isopropyl benzene, acetone, methyl ethyl
ketone, chloroform and carbon tetrachloride.
[0031] Examples of chain transfer agents include thiol-based
compounds such as mercaptoethanol, thioglycerol, thioglycolic acid,
3-mercaptopropionic acid, thiomalic acid, 2-mercaptoethanesulfonic
acid, butanethiol, octanethiol, decanethiol, dodecanethiol,
hexadecanethiol, octadecanethiol, cyclohexyl mercaptan, thiophenol,
octyl thioglycolate or octyl 3-mercaptopropionate; secondary
alcohols such as isopropyl alcohol; and phosphorous acid,
hypophosphorous acid and salts thereof (sodium hypophosphite or
potassium hypophosphite); lower thio oxides such as sulfurous acid,
hydrogen sulfite, dithionous acid or metabisulfurous acid and salts
thereof (sodium hyposulfite, sodium hydrogen sulfite, sodium
dithionite or sodium metabisulfite).
[0032] Polymer (A) can also be obtained by copolymerizing monomers
other than the monomers (a) and (b) within a range that does not
impair the effects of the present invention. The method used to
polymerize other monomers is not particularly specified, other
monomers may be copolymerized after polymerizing the monomers (a)
and (b), or other monomers may be copolymerized together with the
monomers (a) and (b). The other monomers may be any monomers
provided they have a double bond, and examples thereof include
aromatic vinyl monomers such as styrene, vinyl toluene,
2,4-dimethylstyrene, 4-ethylstyrene or 2-vinylnaphthalene;
aliphatic vinyl monomers such as vinyl acetate, vinyl propionate,
vinyl octanoate, methyl vinyl ether, ethyl vinyl ether or
2-ethylhexyl vinyl ether; halogen-based vinyl monomers such as
vinyl chloride, vinyl bromide, vinylidene chloride, allyl chloride
or dichlorostyrene; acrylic esters such as methyl acrylate, ethyl
acrylate, propyl acrylate, butyl acrylate, pentyl acrylate, hexyl
acrylate, heptyl acrylate, octyl acrylate, 2-ethylhexyl acrylate or
nonyl acrylate; and amino group-containing monomers such as allyl
amine, aminoethyl acrylate, aminopropyl acrylate, aminobutyl
acrylate, methylaminoethyl acrylate, 2-diphenylamineacrylamide,
dimethylaminomethyl acrylate, dimethylaminomethyl acrylamide,
N,N-dimethylaminostyrene, 4-vinylstyrene or N-vinylpyrrolidone.
Among these, monomers having an acrylic group are preferable, and
butyl acrylate, pentyl acrylate, hexyl acrylate, heptyl acrylate,
octyl acrylate and 2-ethylhexyl acrylate are more preferable.
[0033] Although a methacrylic group has a structure similar to an
acrylic group, the use of a monomer having a methacrylic group may
cause poor solubility in base oil. In addition, since there are
cases in which extreme pressure performance is not demonstrated or
solubility in base oil becomes poor if the contents of these
monomers are excessively high in the resulting copolymer, the
content of these other monomers in the resulting copolymer is
preferably 30% by weight or less, more preferably 20% by weight or
less, even more preferably 10% by weight or less, and most
preferably these other monomers are substantially not contained.
Furthermore, although monomers (a) and (b) have an acrylic group,
if this group is a methacrylic group, the effects of the present
invention are not obtained, and for example, a copolymer produced
using an alkyl methacrylate and hydroxyalkylene methacrylate does
not allow the obtaining of high extreme pressure performance.
[0034] The lubricating oil composition of the present invention
refers to that obtained by adding the friction and wear reducing
agent for lubricating oil of the present invention to a base oil.
Examples of base oils that can be used include mineral oils such as
paraffin-based mineral oil, naphthene-based mineral oil, refined
mineral oils obtained by refining these oils by hydrorefining,
solvent deasphalting, solvent extraction, solvent dewaxing,
hydrodewaxing, catalytic dewaxing, hydrocracking, alkali
distillation, sulfuric acid treatment or clay treatment; synthetic
oils such as poly-.alpha.-olefins, ethylene-.alpha.-olefin
copolymers, polybutenes, alkyl benzenes, alkyl naphthalenes,
polyphenyl ethers, alkyl-substituted diphenyl ethers, polyol
esters, dibasic acid esters, hindered esters, monoesters or gas to
liquids (GTL), and mixtures of mineral oil with synthetic oil.
[0035] The amount of the friction and wear reducing agent for
lubricating oil of the present invention in the lubricating oil
composition of the present invention is not particularly limited,
but it is preferably added in an amount of 0.1 to 50% by weight,
more preferably 1 to 30% by weight and even more preferably 3 to
20% by weight with respect to the total amount of the lubricating
oil composition. If the amount is less than 0.1% by weight, extreme
pressure performance may be unable to be obtained, while if the
amount exceeds 50% by weight, there are cases in which the friction
and wear reducing agent may not completely dissolve in the base oil
as well as cases in which effects corresponding to the added amount
are not obtained.
[0036] Moreover, the lubricating oil composition of the present
invention does not preclude the addition of known lubricating oil
additives, and additives such as antioxidants, friction reducing
agents, oiliness improvers, cleaning agents, dispersants, viscosity
index improvers, pour point depressants, rust inhibitors, corrosion
inhibitors or antifoaming agents may be added within a range which
does not impair the effects of the present invention.
[0037] Examples of antioxidants include phenol-based antioxidants
such as 2, 6-di-tertiary-butyl phenol (hereinafter, tertiary-butyl
is to be abbreviated as t-butyl), 2,6-di-t-butyl-p-cresol,
2,6-di-t-butyl-4-methylphenol, 2,6-di-t-butyl-4-ethylphenol,
2,4-dimethyl-6-t-butylphenol,
4,4'-methylenebis(2,6-di-t-butylphenol),
4,4'-bis(2,6-di-t-butylphenol), 4,4'-bis(2-methyl-6-t-butylphenol),
2,2'-methylenebis(4-methyl-6-t-butylphenol),
2,2'-methylenebis(4-ethyl-6-t-butylphenol),
4,4'-butylidenebis(3-methyl-6-t-butylphenol),
4,4'-isopropylidenebis(2,6-di-t-butylphenol),
2,2'-methylenebis(4-methyl-6-cyclohexylphenol),
2,2'-methylenebis(4-methyl-6-nonylphenol),
2,2'-isobutylidenebis(4,6-dimethylphenol),
2,6-bis(2'-hydroxy-3'-t-butyl-5'-methylbenzyl)-4-methyl phenol,
3-t-butyl-4-hydroxyanisole, 2-t-butyl-4-hydroxyanisole, octyl
3-(4-hydroxy-3,5-di-t-butylphenyl)propionate, stearyl
3-(4-hydroxy-3,5-di-t-butylphenyl)propionate, oleyl
3-(4-hydroxy-3,5-di-t-butylphenyl)propionate, dodecyl
3-(4-hydroxy-3,5-di-t-butylphenyl)propionate, decyl
3-(4-hydroxy-3,5-di-t-butylphenyl)propionate,
tetrakis{3-(4-hydroxy-3,5-di-t-butylphenyl)propionyloxymethyl}methane,
glycerol 3-(4-hydroxy-3,5-di-t-butylphenyl)propionate monoester,
esters of 3-(4-hydroxy-3,5-di-t-butylphenyl)propionic acid and
glyceryl monooleyl ether, butylene
3-(4-hydroxy-3,5-di-t-butylphenyl)propionate glycol ester, butylene
3-(4-hydroxy-3,5-di-t-butylphenyl)propionate thiodiglycol ester,
4,4'-thiobis(3-methyl-6-t-butylphenol),
4,4'-thiobis(2-methyl-6-t-butylphenol),
2,2'-thiobis(4-methyl-6-t-butylphenol),
2,6-di-t-butyl-.alpha.-dimethylamino-p-cresol,
2,6-di-t-butyl-4-(N,N'-dimethylaminomethylphenol),
bis(3,5-di-t-butyl-4-hydroxybenzyl)sulfide,
tris{(3,5-di-t-butyl-4-hydroxyphenyl)propionyl-oxyethyl}isocyanurate,
tris(3,5-di-t-butyl-4-hydroxyphenyl)isocyanurate,
1,3,5-tris(3,5-di-t-butyl-4-hydroxybenzyl) isocyanurate,
bis{2-methyl-4-(3-n-alkylthiopropionyloxy)-5-t-butylphenyl}sulfide,
1,3,5-tris(4-t-butyl-3-hydroxy-2,6-dimethylbenzyl)isocyanurate,
tetraphthaloyl-di(2,6-dimethyl-4-t-butyl-3-hydroxybenzylsulfide),
6-(4-hydroxy-3,5-di-t-butylanilino)-2,4-bis(octylthio)-1,3,5-triazine,
2,2-thio-{diethyl-bis-3-(3,5-di-t-butyl-4-hydroxyphenyl)}propionate,
N,N'-hexamethylenebis(3,5-di-t-butyl-4-hydroxy-hydrocinnamide),
3,5-di-t-butyl-4-hydroxy-benzyl-phosphate diester,
bis(3-methyl-4-hydroxy-5-t-butylbenzyl)sulfide,
3,9-bis[1,1-dimethyl-2-{.beta.-(3-t-butyl-4-hydroxy-5-methylphenyl)propio-
nyloxy}ethyl]-2,4,8,10-tetraoxaspiro[5,5]undecane,
1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane,
1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene
and bis{3,3'-bis-(4'-hydroxy-3'-t-butylphenyl)butyric acid} glycol
ester; naphthylamine-based antioxidants such as 1-naphthylamine,
phenyl-1-naphthylamine, p-octylphenyl-1-naphthylamine,
p-nonylphenyl-1-naphthylamine, p-dodecylphenyl-1-naphthylamine or
phenyl-2-naphthylamine; phenylenediamine-based antioxidants such as
N,N'-diisopropyl-p-phenylenediamine,
N,N'-diisobutyl-p-phenylenediamine,
N,N'-diphenyl-p-phenylenediamine,
N,N'-di-.beta.-naphthyl-p-phenylenediamine,
N-phenyl-N'-isopropyl-p-phenylenediamine,
N-cyclohexyl-N'-phenyl-p-phenylenediamine,
N-1,3-dimethylbutyl-N'-phenyl-p-phenylenediamine,
dioctyl-p-phenylenediamine, phenylhexyl-p-phenylenediamine or
phenyloctyl-p-phenylenediamine; diphenylamine-based antioxidants
such as dipyridylamine, diphenylamine,
p,p'-di-n-butyldiphenylamine, p,p'-di-t-butyldiphenylamine,
p,p'-di-t-pentyldiphenylamine, p,p'-dioctyldiphenylamine,
p,p'-dinonyldiphenylamine, p,p'-didecyldiphenylamine,
p,p'-didodecyldiphenylamine, p,p'-distyryldiphenylamine,
p,p'-dimethoxydiphenylamine,
4,4'-bis(4-.alpha.,.alpha.-dimethylbenzoyl)diphenylamine,
p-isopropoxydiphenylamine or dipyridylamine; phenothiazine-based
antioxidants such as phenothiazine, N-methylphenothiazine,
N-ethylphenothiazine, 3,7-dioctylphenothiazine, phenothiazine
carboxylic acid ester or phenoselenazine; and, zinc
dithiophosphate. The amount of these antioxidants is preferably
0.01 to 5%, by weight and more preferably 0.05 to 4% by weight with
respect to the base oil.
[0038] Examples of friction reducing agents include organic
molybdenum compounds such as oxymolybdenum dithiocarbamate sulfide
or oxymolybdenum dithiophosphate sulfide. The amount of these
friction reducing agents in terms of the content of molybdenum is
preferably 30 to 2,000 wtppm and more preferably 50 to 1,000 wtppm
with respect to the base oil.
[0039] Examples of oiliness improvers include higher alcohols such
as oleyl alcohol or stearyl alcohol; fatty acids such as oleic acid
or stearic acid; esters such as oleyl glycerol ester, stearyl
glycerol ester or lauryl glycerol ester; amides such as lauryl
amide, oleyl amide or stearyl amide; amines such as lauryl amine,
oleyl amine or stearyl amine; and ethers such as lauryl glyceryl
ether or oleyl glyceryl ether. The amount of these oiliness
improvers is preferably 0.1 to 5% by weight and more preferably 0.2
to 3% by weight with respect to the base oil.
[0040] Examples of cleaning agents include sulfonates, phenates,
salicylates and phosphates of calcium, magnesium or barium and
perbasic salts thereof. Among these, perbasic salts are preferable,
and among perbasic salts, those having a total base number (TBN) of
30 to 500 mgKOH are more preferable. Moreover, salicylate-based
cleaning agents free of phosphor and sulfur atoms are also
preferable. The amount of these cleaning agents is preferably 0.5
to 10% by weight and more preferably 1 to 8% by weight with respect
to the base oil.
[0041] Examples of dispersants include succinic acid imides,
succinic acid esters, benzylamines and boric acid modification
products thereof, to which have been added an alkyl group or
alkenyl group, having a weight average molecular weight of about
500 to 3,000. The amount of these dispersants is preferably 0.5 to
10% by weight and more preferably 1 to 8% by weight based with
respect to the base oil.
[0042] Examples of viscosity index improvers include
poly(C1-18)alkyl(meth)acrylates, (C1-18)alkyl
acrylate/(C1-18)alkyl(meth)acrylate copolymers,
diethylaminoethyl(meth)acrylate/(C1-18)alkyl(meth)acrylate
copolymers, ethylene/(C1-18)alkyl(meth)acrylate copolymers,
polyisobutylene, polyalkylstyrene, ethylene/propylene copolymers,
styrene/maleic acid ester copolymers and styrene/isoprene
hydrogenated polymers. Alternatively, dispersible or
multifunctional viscosity index improvers to which dispersing
properties are imparted may also be used. The average molecular
weight is about 10,000 to 1,500,000. The amount of these viscosity
index improvers is preferably 0.1 to 20% by weight and more
preferably 0.3 to 15% by weight with respect to the base oil.
Furthermore, a methacrylate-based polymer is preferably used for
the viscosity index improver. This is because methacrylate-based
polymers demonstrate superior performance as viscosity index
improvers in comparison with acrylate-based polymers.
Acrylate-based polymers are known to demonstrate barely any
function as viscosity index improvers, and although the friction
and wear reducing agent of the present invention has a structure
that resembles that of a specific viscosity index improver, it does
not function as a viscosity index improver.
[0043] Examples of pour point depressants include poly(alkyl
methacrylates), poly(alkyl acrylates), poly(alkyl styrenes) and
polyvinyl acetate having a weight average molecular weight of 1,000
to 100,000. The amount of these pour point depressants is
preferably 0.005 to 3% by weight and more preferably 0.01 to 2% by
weight with respect to the base oil. Methacrylate-based polymers
are preferable for the pour point depressant as well as viscosity
index improvers, and the friction and wear reducing agent of the
present invention demonstrates barely any function as a pour point
depressant.
[0044] Examples of rust inhibitors include sodium nitrite, calcium
salts of oxidized paraffin wax, magnesium salts of oxidized
paraffin wax, tallow acid alkaline metal salts, alkaline earth
metal salts or amine salts, alkenyl succinic acids or alkenyl
succinic acid hemiesters (in which the molecular weight of the
alkenyl group is about 100 to 300), sorbitan monoesters,
nonylphenol ethoxylates and calcium salts of lanolin fatty acid.
The amount of these rust inhibitors is preferably 0.01 to 3% by
weight and more preferably 0.02 to 2% by weight with respect to the
base oil.
[0045] Examples of corrosion inhibitors include benzotriazole,
benzimidazole, benzothiazole, benzothiadiazole and
tetraalkylthiuram disulfide. The amount of these corrosion
inhibitors is preferably 0.01 to 3% by weight and more preferably
0.02 to 2% by weight with respect to the base oil.
[0046] Examples of antifoaming agents include polydimethyl
silicone, trifluoropropylmethyl silicone, colloidal silica,
poly(alkyl acrylates), poly(alkyl methacrylates), alcohol
ethoxy/propoxylates, fatty acid ethoxy/propoxylates and sorbitan
partial fatty acid esters. The amount of these antifoaming agents
is preferably 0.001 to 0.1% by weight and more preferably 0.001 to
0.01% by weight with respect to the base oil.
[0047] The lubricating oil composition of the present invention can
be used in any lubricating application. For example, it may be used
in lubricating oil such as engine oil, gear oil, turbine oil,
hydraulic oil, fire-resistant hydraulic fluid, refrigerator oil,
compressor oil, vacuum pump oil, bearing oil, insulating oil,
sliding surface oil, rock drill oil, metalworking oil, plastic
working oil, heat treating oil or grease. Among these, the
lubricating oil composition of the present invention is preferably
used in engine oil, bearing oil or grease, and most preferably used
in engine oil.
EXAMPLES
[0048] The following provides a detailed explanation of the present
invention through examples thereof.
[0049] Polymers used in testing were produced using the monomers
described below.
[0050] a-1: Decyl acrylate (R.sup.1=decyl group in general formula
(1))
[0051] a-2: Dodecyl acrylate (R.sup.1=dodecyl group in general
formula (1))
[0052] a-3: Octadecyl acrylate (R.sup.1=octadecyl group in general
formula (1))
[0053] a-4: Butyl acrylate (R.sup.1=butyl group in general formula
(1))
[0054] a-5: 2-ethylhexyl acrylate (R.sup.1=2-ethylhexyl group in
general formula (1))
[0055] a-6: Dodecyl methacrylate
[0056] a-7: Hexadecyl methacrylate
[0057] b-1: 2-hydroxyethyl acrylate (R.sup.2=ethylene group in
general formula (2))
[0058] b-2: 2-hydroxypropyl acrylate (R.sup.2=propylene group in
general formula (2))
[0059] b-3: 2-hydroxyethyl methacrylate
[0060] b-4: N,N-dimethylaminoethyl acrylate
[0061] GPC was carried out under the following conditions.
[0062] GPC system: Semi-micro HPLC 7400 (GL Sciences)
[0063] Columns: Four columns consisting of the GPC KF-401HQ, GPC
KF-402.5 and two GPC LF-404 columns and connected in series (all
manufactured by Showa Denko)
[0064] Detector: GL-7454 (GL Sciences)
[0065] Flow rate: 0.3 ml/min
[0066] Sample concentration: 0.2% by weight (THF solution)
[0067] Sample volume: 5 .mu.l
[0068] Column temperature: 40.degree. C.
[0069] Molecular weights were calculated by comparing with a
styrene standard.
[0070] <Synthesis of Sample 1>
[0071] 144 g (0.6 moles) of dodecyl acrylate (a-2) as monomer (a),
46 g (0.4 moles) of 2-hydroxyethyl acrylate (b-1) as monomer (b)
and 190 g of 2-propanol as solvent were charged into a four-necked
flask having a volume of 500 ml and equipped with a thermometer,
nitrogen introduction tube and stirrer. The inside of the flask was
replaced with nitrogen, and after adding 0.8 g of
2,2'-azobis(2-methylpropionitrile) as an initiator, the temperature
was raised slowly while stirring and the contents were allowed to
react for 5 hours while refluxing at a temperature of 75.degree. C.
to 85.degree. C. to obtain Sample 1. The monomer ratio of Sample 1
was monomer (a)/monomer (b)=60/40 (molar ratio), and as a result of
measuring molecular weight by GPC, the weight average molecular
weight in terms of styrene was 22,000.
[0072] <Synthesis of Sample 2>
[0073] Sample 2 having a monomer ratio of monomer (a)/monomer
(b)=60/40 (molar ratio) was obtained by the same method and using
the same apparatus as Sample 1 with the exception of changing the
solvent from 2-propanol to a mixture of 2-propanol and dioxane
(weight ratio of 2-propanol/dioxane=5/5). As a result of measuring
the molecular weight of Sample 2 by GPC, the weight average
molecular weight thereof in terms of styrene was 28,000.
[0074] <Synthesis of Sample 3>
[0075] Sample 3 having a monomer ratio of monomer (a)/monomer
(b)=60/40 (molar ratio) was obtained by the same method and using
the same apparatus as Sample 1 with the exception of changing the
solvent from 2-propanol to a mixture of 2-propanol and dioxane
(weight ratio of 2-propanol/dioxane=1/9). As a result of measuring
the molecular weight of Sample 3 by GPC, the weight average
molecular weight thereof based on styrene was 45,000.
[0076] <Synthesis of Sample 4>
[0077] Sample 4 having a monomer ratio of monomer (a)/monomer
(b)=60/40 (molar ratio) was obtained by the same method and using
the same apparatus as Sample 1 with the exception of changing the
solvent from 2-propanol to dioxane. As a result of measuring the
molecular weight of Sample 4 by GPC, the weight average molecular
weight thereof in terms of styrene was 230,000.
[0078] <Synthesis of Sample 5>
[0079] Sample 5 having a monomer ratio such that monomer
(a)/monomer (b)=60/40 (molar ratio) was obtained by the same method
and using the same apparatus as Sample 1 with the exception of
changing the solvent from 2-propanol to dioxane and further adding
1 g of dodecanethiol as a chain transfer agent immediately prior to
addition of the catalyst. As a result of measuring the molecular
weight of Sample 5 by GPC, the weight average molecular weight
thereof in terms of styrene was 38,000.
[0080] <Synthesis of Samples 6 to 18>
[0081] Samples 6 to 18 having different types and ratios of monomer
(a) and monomer (b) were obtained by the same method and using the
same apparatus of Sample 1 with the exception of changing the types
and ratio of monomer (a) and monomer (b). The compositions of
Samples 6 to 18 and the results of measuring the molecular weights
thereof by GPC are shown in Table 1.
TABLE-US-00001 TABLE 1 Types of Monomers Monomer Molar Ratio
Molecular (a) (b) (a) (b) Weight Sample 1 a-2 b-1 60 40 22,000
Sample 2 a-2 b-1 60 40 28,000 Sample 3 a-2 b-1 60 40 45,000 Sample
4 a-2 b-1 60 40 230,000 Sample 5 a-2 b-1 60 40 38,000 Sample 6 a-2
b-1 40 60 28,000 Sample 7 a-2 b-1 50 50 25,000 Sample 8 a-2 b-1 70
30 23,000 Sample 9 a-2 b-1 80 20 24,000 Sample 10 a-2 b-1 95 5
20,000 Sample 11 a-1 b-2 60 40 19,000 Sample 12 a-3 b-2 60 40
35,000 Sample 13 a-2 b-3 60 40 22,000 Sample 14 a-2 b-4 60 40
21,000 Sample 15 a-4 b-1 60 40 18,500 Sample 16 a-5 b-1 60 40
20,500 Sample 17 a-6 b-1 60 40 23,000 Sample 18 a-7 b-1 60 40
25,500
[0082] Other Samples
[0083] Sample 19: Tricresyl phosphate
[0084] Sample 20: Chlorinated paraffin (chlorine content: 40% by
weight)
[0085] Sample 21: Glyceryl monooleyl ester
[0086] Furthermore, among the above-mentioned Samples 1 to 21,
examples of the present invention correspond to Samples 1, 2, 5, 7,
8, 9, 11 and 12, while the other samples are comparative
examples.
[0087] <Friction Test>
[0088] The above-mentioned Samples 1 to 21 were heated and
dissolved in the following base oils to a concentration of 5% by
weight (the added amount in terms of solid content) followed by
measuring the coefficients of friction thereof using a shell-type
high-speed four-ball tester. More specifically, the test method
comprised measuring the coefficient of friction under conditions of
a rotating speed of 300 rpm, load of 10 kgf and temperature of
40.degree. C. Furthermore, the base oils to which Sample 4, 17 or
18 was added became uniform solutions by heating them, and although
precipitates formed when returned to room temperature, sampling was
carried out while still in a uniform state and those samples were
immediately used in testing. In addition, since Samples 6, 15 and
16 did not dissolve even if the base oil was heated to 100.degree.
C., testing was not carried out on those samples.
[0089] Base Oil 1: Mineral oil, kinematic viscosity: 4.24
mm.sup.2/S (100.degree. C.), 19.65 mm.sup.2/S (40.degree. C.),
viscosity index: 126
[0090] Base Oil 2: Synthetic oil (poly-.alpha.-olefin), kinematic
viscosity: 4.0 mm.sup.2/S (100.degree. C.), 18.4 mm.sup.2/S
(40.degree. C.), viscosity index: 119
[0091] <Extreme Pressure Test>
[0092] The above-mentioned Samples 1 to 21 were heated and
dissolved in the same base oil as that used in the friction test to
a concentration of 1% by weight (the added amount in terms of on
solid content) to prepare test solutions followed by measuring the
wear track diameters of the test pieces using an SRV tester (SRV
Type III, Optimol). The test conditions comprised placing a
spherical test piece on a flat test piece having 1 ml of test
solution placed thereon, and after sliding the spherical test piece
back and forth for 60 minutes at a load of 100 N, amplitude of 1 mm
and frequency of 50 Hz, the diameter of the wear track present on
the spherical test piece was measured. Furthermore, a uniform
solution resulted following heating of the base oil added in
Samples 4, 17 and 18, and although a precipitate formed when
returned to room temperature, sampling was carried out while still
in a uniform state and those samples were immediately used in
testing. In addition, since Samples 6, 15 and 16 did not dissolve
even if the base oil was heated to 100.degree. C., testing was not
carried out on those samples.
TABLE-US-00002 TABLE 2 Friction Test Extreme Pressure Base
(Coefficient of Test (wear track Sample Oil Friction) diameter: mm)
Examples 1 1 1 0.11 0.41 2 2 1 0.11 0.43 3 5 1 0.12 0.45 4 7 1 0.13
0.41 5 8 1 0.12 0.45 6 9 1 0.12 0.46 7 11 1 0.11 0.44 8 12 1 0.12
0.47 9 1 2 0.11 0.42 10 2 2 0.12 0.45 Comp. 1 3 1 0.17 0.45
Examples 2 4 1 0.18 0.47 3 6 1 -- -- 4 10 1 0.17 0.58 5 13 1 0.16
0.62 6 14 1 0.16 0.50 7 15 1 -- -- 8 16 1 -- -- 9 17 1 0.17 0.63 10
18 1 0.16 0.65 11 19 1 0.18 0.46 12 20 1 0.23 0.72 13 21 1 0.12
0.67 14 3 2 0.18 0.47 15 -- 1 0.21 0.63 16 -- 2 0.23 0.65
[0093] *Test results of Comparative Example 15 and 16 indicate
those obtained by using only Base Oil 1 and Base Oil 2,
respectively.
[0094] Although friction cannot be considered to be low unless the
coefficient of friction is at least below 0.15, polymers having a
molecular weight in excess of 40,000 did not demonstrate a
coefficient of friction below 0.15 even if produced with monomers
used in the present application. On the other hand, since the
results of the extreme pressure test using methacrylic polymers
shows a wear track diameter of 0.62 mm in Comparative Example 5,
0.63 mm in Comparative Example 9 and 0.65 mm in Comparative Example
10 with respect to 0.63 mm for the Comparative Example using only
base oil, methacrylic polymers were confirmed to demonstrate hardly
any extreme pressure performance or conversely exacerbate extreme
pressure performance.
* * * * *