U.S. patent application number 13/580485 was filed with the patent office on 2013-05-09 for lubricant compositions and rolling device.
This patent application is currently assigned to NSK LTD.. The applicant listed for this patent is Koichi Hachiya, Kanako Mori, Atsushi Yokouchi. Invention is credited to Koichi Hachiya, Kanako Mori, Atsushi Yokouchi.
Application Number | 20130116158 13/580485 |
Document ID | / |
Family ID | 47356826 |
Filed Date | 2013-05-09 |
United States Patent
Application |
20130116158 |
Kind Code |
A1 |
Hachiya; Koichi ; et
al. |
May 9, 2013 |
LUBRICANT COMPOSITIONS AND ROLLING DEVICE
Abstract
The lubricant compositions of the invention include a saturated
fatty acid triglyceride as a lubricating ingredient and further
contain an antioxidant or a thickener which is magnesium stearate
or calcium stearate. Consequently, the lubricant compositions are
harmless even when eaten, have excellent lubricity, and impose
little burden on the environment. The rolling device of the
invention not only imposes little burden on the environment because
the device is lubricated with either of these lubricant
compositions, but also has excellent durability.
Inventors: |
Hachiya; Koichi; (Kanagawa,
JP) ; Mori; Kanako; (Kanagawa, JP) ; Yokouchi;
Atsushi; (Kanagawa, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Hachiya; Koichi
Mori; Kanako
Yokouchi; Atsushi |
Kanagawa
Kanagawa
Kanagawa |
|
JP
JP
JP |
|
|
Assignee: |
NSK LTD.
Tokyo
JP
|
Family ID: |
47356826 |
Appl. No.: |
13/580485 |
Filed: |
January 23, 2012 |
PCT Filed: |
January 23, 2012 |
PCT NO: |
PCT/JP2012/051322 |
371 Date: |
August 22, 2012 |
Current U.S.
Class: |
508/506 ;
508/512 |
Current CPC
Class: |
C10M 2207/1285 20130101;
F16C 19/06 20130101; C10M 169/00 20130101; C10M 169/06 20130101;
C10M 2207/026 20130101; C10M 2207/1256 20130101; C10M 2215/064
20130101; C10M 169/04 20130101; C10M 2215/1026 20130101; C10M
2203/024 20130101; C10N 2030/64 20200501; C10M 2207/126 20130101;
C10N 2010/04 20130101; F16C 33/6633 20130101; C10M 2215/065
20130101; C10M 2219/06 20130101; C10N 2040/02 20130101; F16C
33/6607 20130101; C10M 129/26 20130101; C10M 2215/102 20130101;
C10M 2207/1265 20130101; C10M 2207/08 20130101; C10M 2207/281
20130101; C10M 2207/046 20130101; C10N 2050/10 20130101; C10M
2207/2835 20130101; C10M 2207/401 20130101; C10N 2030/06 20130101;
C10M 2203/022 20130101; C10M 2207/125 20130101; C10M 2203/02
20130101; C10M 2207/283 20130101 |
Class at
Publication: |
508/506 ;
508/512 |
International
Class: |
C10M 129/26 20060101
C10M129/26 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 15, 2011 |
JP |
2011-133118 |
Nov 30, 2011 |
JP |
2011-262944 |
Nov 30, 2011 |
JP |
2011-262945 |
Claims
1-6. (canceled)
7. A lubricant composition which comprises a saturated fatty acid
triglyceride and an antioxidant.
8. The lubricant composition as claimed in claim 7, wherein the
antioxidant comprises at least one member selected from phenols,
polyphenols, flavonoids, carotenoids, vitamins, vitamin analogues,
and organic acids.
9. The lubricant composition as claimed in claim 7 or 8, which
contains a coenzyme Q.
10. The lubricant composition as claimed in claim 7 or 8, which
contains a fatty acid ester, a metal soap, or a urea compound as a
thickener.
11. The lubricant composition as claimed in claim 9, which contains
a fatty acid ester, a metal soap, or a urea compound as a
thickener.
12. A lubricant composition which comprises a saturated fatty acid
triglyceride as a base oil and either magnesium stearate or calcium
stearate as a thickener.
13. A rolling device equipped with an inner member which has a
raceway surface in the outer surface thereof, an outer member which
has a raceway surface that faces the raceway surface of the inner
member and which has been disposed outside the inner member, a
plurality of rolling elements which have been disposed between the
two raceway surfaces so as to be freely rollable, and a lubricant
which lubricates between each raceway surface and the rolling
elements, wherein the lubricant is the lubricant composition
according to claim 7 or 8.
14. A rolling device equipped with an inner member which has a
raceway surface in the outer surface thereof, an outer member which
has a raceway surface that faces the raceway surface of the inner
member and which has been disposed outside the inner member, a
plurality of rolling elements which have been disposed between the
two raceway surfaces so as to be freely rollable, and a lubricant
which lubricates between each raceway surface and the rolling
elements, wherein the lubricant is the lubricant composition
according to claim 9.
15. A rolling device equipped with an inner member which has a
raceway surface in the outer surface thereof, an outer member which
has a raceway surface that faces the raceway surface of the inner
member and which has been disposed outside the inner member, a
plurality of rolling elements which have been disposed between the
two raceway surfaces so as to be freely rollable, and a lubricant
which lubricates between each raceway surface and the rolling
elements, wherein the lubricant is the lubricant composition
according to claim 10.
16. A rolling device equipped with an inner member which has a
raceway surface in the outer surface thereof, an outer member which
has a raceway surface that faces the raceway surface of the inner
member and which has been disposed outside the inner member, a
plurality of rolling elements which have been disposed between the
two raceway surfaces so as to be freely rollable, and a lubricant
which lubricates between each raceway surface and the rolling
elements, wherein the lubricant is the lubricant composition
according to claim 11.
17. A rolling device equipped with an inner member which has a
raceway surface in the outer surface thereof, an outer member which
has a raceway surface that faces the raceway surface of the inner
member and which has been disposed outside the inner member, a
plurality of rolling elements which have been disposed between the
two raceway surfaces so as to be freely rollable, and a lubricant
which lubricates between each raceway surface and the rolling
elements, wherein the lubricant is the lubricant composition
according to claim 12.
Description
TECHNICAL FIELD
[0001] The present invention relates to lubricant compositions. The
invention further relates to a rolling device, e.g., a rolling
bearing, ball screw, linear guide, or direct-acting bearing.
BACKGROUND ART
[0002] Lubricant compositions such as lubricating oils and greases
have conventionally been used in the sliding parts or rotating or
rolling parts of various machines and apparatus (see, for example,
patent documents 1 to 3). However, most of the conventionally known
lubricant compositions including those of patent documents 1 to 3
are not eatable, and there are few known lubricant compositions,
among the lubricant compositions usable for lubricating machine
parts including rolling bearings, that are harmless even when
eaten.
[0003] There are frequently cases where oxidation inhibitors are
added to lubricant compositions to improve the durability thereof,
because the temperature of the lubricant compositions rises with
operation of the rolling devices. The oxidation inhibitors for
addition to lubricant compositions include the following.
Frequently used for industrial applications are amine-based
antioxidants, phenolic antioxidants, and phenothiazine. There are
cases where tocopherol (vitamin E), dibutyl-p-cresol (DBPC),
butylhydroxyanisole (BHA), butylhydroquinone (TBHQ), isopropyl
gallate, and the like are used in machines for foods, although such
cases are rare (see, for example, patent documents 4 to 6).
However, there is considerable concern about environmental
preservation, and there is a strong desire for a technique which
imposes little environmental burden and, despite this, further
enhances the effect of oxidation prevention.
PRIOR-ART DOCUMENTS
Patent Documents
[0004] Patent Document 1: Japanese Patent No. 4730714 [0005] Patent
Document 2: JP-T-2004-510020 [0006] Patent Document 3:
JP-A-2007-64456 [0007] Patent Document 4: JP-A-2002-323053 [0008]
Patent Document 5: JP-A-2008-248990 [0009] Patent Document 6:
JP-A-4-72392
SUMMARY OF THE INVENTION
Problems that the Invention is to Solve
[0010] An object of the invention, which has been achieved in view
of the circumstances described above, is to provide lubricant
compositions which are harmless even when eaten, have excellent
lubricity, and impose little environmental burden and which,
despite this, are highly prevented from oxidizing. Another object
is to provide a rolling device which is lubricant with either of
the lubricant compositions, imposes little environmental burden,
and is excellent in terms of lubrication and durability.
Means for Solving the Problems
[0011] The present invention provides the following lubricant
compositions and rolling device in order to overcome those
problems. [0012] (1) A lubricant composition characterized by
comprising a saturated fatty acid triglyceride and an antioxidant.
[0013] (2) The lubricant composition according to (1) above
characterized in that the antioxidant comprises at least one member
selected from phenols, polyphenols, flavonoids, carotenoids,
vitamins, vitamin analogues, and organic acids. [0014] (3) The
lubricant composition according to (1) or (2) above characterized
by containing a coenzyme Q. [0015] (4) The lubricant composition
according to any one of (1) to (3) above characterized by
containing a fatty acid ester, a metal soap, or a urea compound as
a thickener. [0016] (5) A lubricant composition characterized by
comprising a saturated fatty acid triglyceride as a base oil and
either magnesium stearate or calcium stearate as a thickener.
[0017] (6) A rolling device equipped with an inner member which has
a raceway surface in the outer surface thereof, an outer member
which has a raceway surface that faces the raceway surface of the
inner member and which has been disposed outside the inner member,
a plurality of rolling elements which have been disposed between
the two raceway surfaces so as to be freely rollable, and a
lubricant which lubricates between each raceway surface and the
rolling elements, characterized in that the lubricant is the
lubricant composition according to any one of (1) to (5) above.
Effects of the Invention
[0018] The lubricant compositions of the invention are harmless
even when eaten, and impose little environmental burden. Despite
this, the compositions are highly prevented from oxidizing. The
rolling device of the invention has excellent durability, imposes
little environmental burden, and causes no harm even when the
lubricant composition is eaten.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a sectional view which illustrates a deep-groove
ball bearing as one embodiment of the rolling device of the
invention.
[0020] FIG. 2 is a graph which shows the results of (Test 1)
conducted in Example A.
[0021] FIG. 3 is a graph that shows the results of an examination
in which the test greases of Examples 4A, 5A, and 6A and
Comparative Examples 20A and 21A were examined for bearing life in
(Test 2) in Example A.
[0022] FIG. 4 is a graph that shows the results of an examination
in which the test greases of Examples 7A and 8A and Comparative
Examples 22A and 23A were examined for bearing life in (Test 2) in
Example A.
[0023] FIG. 5 is a graph which shows the results of a life test
conducted in Example B.
[0024] FIG. 6 is a graph which shows the results of another life
test conducted in Example B.
[0025] FIG. 7 is a graph which shows the results of still another
life test conducted in Example B.
[0026] FIG. 8 is a graph which shows the results of Example C.
[0027] FIG. 9 is a graph which shows the results of Example D.
MODES FOR CARRYING OUT THE INVENTION
[0028] The invention will be explained below in detail.
(Lubricant Compositions)
[0029] One of the lubricant compositions of the invention includes
a saturated fatty acid triglyceride as a lubricating ingredient and
an antioxidant as an oxidation inhibitor.
[0030] The saturated fatty acid triglyceride is an ester of one or
more saturated fatty acids with glycerol, and has biodegradability.
The kinds of the saturated fatty acids are not particularly
limited. However, linear fatty acids are preferred, and saturated
fatty acids having 6-12 carbon atoms are preferred. In case where
the saturated fatty acids each have 5 or less carbon atoms, there
is the possibility that the base oil might have insufficient heat
resistance. In case where the saturated fatty acids each have more
than 12 carbon atoms, there is the possibility that the base oil
might have too high a viscosity. Preferred of those are saturated
fatty acids having 8-12 carbon atoms. Even more preferred are
saturated fatty acids having 8-10 carbon atoms. Such saturated
fatty acids have excellent lubricity and are available on the
market at relatively low cost.
[0031] One saturated fatty acid triglyceride may be used alone, or
a plurality of saturated fatty acid triglycerides may be used as a
mixture thereof. Furthermore, the saturated fatty acid triglyceride
may be either a saturated fatty acid triglyceride obtained by the
reaction of three molecules of one saturated fatty acid with one
molecule of glycerol or a saturated fatty acid triglyceride
obtained by the reaction of three molecules, in total, of two or
three saturated fatty acids with one molecule of glycerol.
[0032] In the case where a plurality of saturated fatty acid
triglycerides are used as a mixture thereof, it is preferred that
the mixture should be a mixture of a saturated fatty acid
triglyceride which is an ester of a saturated fatty acid having 8
carbon atoms with glycerol (referred to as saturated fatty acid
triglyceride A) and a saturated fatty acid triglyceride which is an
ester of a saturated fatty acid having 10 carbon atoms with
glycerol (referred to as saturated fatty acid triglyceride B). In
this case, the molar ratio of the saturated fatty acid triglyceride
A to the saturated fatty acid triglyceride B (A:B) is preferably in
the range of 60:40 to 90:10, more preferably in the range of 70:30
to 80:20. When the molar ratio is regulated so as to be within such
a range, the lubricant composition has better chemical performance,
e.g., heat resistance and durability, and better mechanical
performance, not to mention better low-torque characteristics.
[0033] In the case where a saturated fatty acid triglyceride
obtained by the reaction of three molecules, in total, of two or
three saturated fatty acids with one molecule of glycerol is used,
it is preferred that this triglyceride should be a saturated fatty
acid triglyceride obtained by the reaction of three molecules, in
total, of a saturated fatty acid having 8 carbon atoms and a
saturated fatty acid having 10 carbon atoms with one molecule of
glycerol. In this case, the molar ratio of the saturated fatty acid
ingredient having 8 carbon atoms (C) to the saturated fatty acid
ingredient having 10 carbon atoms (D) (C:D) is preferably in the
range of 60:40 to 90:10, more preferably in the range of 70:30 to
80:20. When the molar ratio is regulated so as to be within such a
range, the lubricant composition has better chemical performance,
e.g., heat resistance and durability, and better mechanical
performance, not to mention better low-torque characteristics.
[0034] The molar ratio (C:D) can be regulated, for example, by
mixing, in a suitable proportion, a saturated fatty acid
triglyceride obtained by the reaction of one molecule of the
saturated fatty acid having 8 carbon atoms and two molecules of the
saturated fatty acid having 10 carbon atoms with one molecule of
glycerol and a saturated fatty acid triglyceride obtained by the
reaction of two molecules of the saturated fatty acid having 8
carbon atoms and one molecule of the saturated fatty acid having 10
carbon atoms with one molecule of glycerol.
[0035] It is preferred that the saturated fatty acid triglyceride
should have a dynamic viscosity at 40.degree. C. of 8-120
mm.sup.2/s. In case where the dynamic viscosity at 40.degree. C.
thereof is less than 8 mm.sup.2/s, there is the possibility that
the base oil might have insufficient heat resistance. In case where
the dynamic viscosity at 40.degree. C. thereof exceeds 120
mm.sup.2/s, this base oil has increased shear resistance and there
is the possibility that use of this lubricant composition in, for
example, a rolling bearing might disadvantageously result in an
increase in starting torque or rotation torque. From the standpoint
of inhibiting such troubles from occurring, the dynamic viscosity
at 40.degree. C. of the saturated fatty acid triglyceride is more
preferably 8-50 mm.sup.2/s, even more preferably 10-35 mm.sup.2/s,
most preferably 10-20 mm.sup.2/s.
[0036] It is preferred that the lubricant composition should
consist only of one or more saturated fatty acid triglycerides or
contain one or more saturated fatty acid triglycerides as the main
component. However, another kind of oil which is used as a base oil
in general lubricants may be mixed with the saturated fatty acid
triglyceride(s) so long as the oil is incorporated in such an
amount that the objects of the invention are accomplished. For
example, a natural lubricating oil such as an animal or vegetable
oil is preferred. Examples thereof include beef tallow, lard,
soybean oil, rapeseed oil, rice bran oil, coconut oil, palm oil,
and palm kernel oil or products of hydrogenation of these.
[0037] The antioxidant may be an antioxidant which is in use as a
food additive. Thus, the lubricant composition or the rolling
device, e.g., a rolling bearing, that is equipped with the
lubricant composition is rendered usable in machines for foods,
machines for medicines, etc. Examples of such antioxidant include
phenols, polyphenols, flavonoids, carotenoids, vitamins, vitamin
analogues, and organic acids.
[0038] Examples of the phenols include BHA, butylhydroxytoluene
(BHT), and TBHQ.
[0039] Examples of the polyphenols include grape seed extract,
proanthocyanidin, and oil-soluble catechins.
[0040] Examples of the flavonoids include soybean isoflavone.
[0041] Examples of the cateroids include .beta.-carotene, lycopene,
and astaxanthin.
[0042] Examples of the vitamins include vitamin A substances,
vitamin B substances, vitamin C substances, vitamin D substances,
vitamin E substances, and vitamin K substances. Examples of the
vitamin A substances include retinal, retinol, retinoic acid, and
dehydroretinal. Examples of the vitamin B substances include
thiamine, thiamine disulfide, dicethiamine, octotiamine,
cycotiamine, bisibuthiamine, bisbentiamine, prosultiamine,
benfotiamine, fursultiamine, riboflavin, flavin adenine
dinucleotide, pyridoxine, pyridoxal, hydroxocobalamin,
cyanocobalamin, methylcobalamin, deoxyadenocobalamin, folic acid,
tetrahydrofolic acid, dihydrofolic acid, nicotinic acid,
nicotinamide, nicotinyl alcohol, pantothenic acid, panthenol,
biotin, choline, and inositol.
[0043] Examples of the vitamin C substances include ascorbic acid
and derivatives thereof and erythorbic acid and derivatives
thereof. Examples of the vitamin D substances include
ergocalciferol, cholecalciferol, hydroxycholecalciferol,
dihydroxycholecalciferol, and dihydrotachysterol. Examples of the
vitamin E substances include tocopherols, derivatives thereof, and
ubiquinone derivatives. The tocopherols are not particularly
limited, and examples thereof include d-.alpha.-tocopherol,
d-.beta.-tocopherol, d-.gamma.-tocopherol, d-.delta.-tocopherol,
and dl-.alpha.-tocopherol. A mixture of these tocopherols may be
used. Examples of the vitamin K substances include phytonadione,
menaquinone, menadione, menadiol, an extract of fermented soybeans,
and an extract of Bacillus natto. Examples of other vitamin
substances include carnitine, ferulic acid, .gamma.-orizanol,
orotic acid, rutin, eriocitrin, and hesperidin.
[0044] Examples of the vitamin analogues include thioctic acid
(.alpha.-liboic acid) and ubiquinol.
[0045] Examples of the organic acids include phytic acid.
[0046] One of these antioxidants may be used alone, or a suitable
combination of two or more thereof may be used. To use two or more
thereof in combination further enhances the effect of preventing
oxidation.
[0047] The content of the antioxidant in the lubricant composition
is an amount with which the effect of preventing oxidation can be
imparted. The content thereof can be regulated in accordance with
the kind of the lubricating ingredient, use, etc. For example, in
the case of a grease composition to be enclosed in bearings, a
sufficient oxidation-preventing effect is obtained by incorporating
the antioxidant in an amount of 0.1-10% by mass based on the whole
grease.
[0048] It is preferred to add a coenzyme Q to the lubricant
composition, because the addition thereof further enhances the
oxidation-preventing effect. Although the kind of the coenzyme Q is
not particularly limited, coenzyme Q10 is especially preferred. One
coenzyme Q may be used alone, or a suitable combination of two or
more coenzymes Q may be used.
[0049] Furthermore, a thickener may be incorporated to produce a
grease composition. Examples of the thickener include metal soaps
such as aluminum soaps, barium soaps, calcium soaps, lithium soaps,
sodium soaps, lithium complex soaps, calcium complex soaps, and
aluminum complex soaps. Also usable are urea compounds such as
diurea, triurea, tetraurea, and polyurea, urethane compounds,
urea-urethane compounds, sodium terephthalamate, and the like.
Moreover, gellants, such as amino acid-based gellants and
polysaccharide esters, are also usable.
[0050] Furthermore, a dextrin fatty acid ester, which is obtained
from a fatty acid and dextrin, or an inulin fatty acid ester, which
is obtained from a fatty acid and inulin, can also be used as a
thickener. Since these esters are materials derived from natural
substances, the burden to be imposed on the environment is
lessened. It is, however, noted that in the case where a dextrin
fatty acid ester or an inulin fatty acid ester is used, various
bacteria are apt to propagate and the grease composition is apt to
be deteriorated by the propagation of bacteria. This bacterial
deterioration of the grease composition can be inhibited by using,
as an antioxidant, thioctic acid in combination with at least one
member selected from vitamin E substances and polyphenols.
[0051] It is preferred that the fatty acids of the dextrin fatty
acid ester and inulin fatty acid ester should be saturated fatty
acids having 6-24 carbon atoms. Examples thereof include hexanoic
acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid,
dodecanoic acid, tetradecanoic acid, pentadecanoic acid,
hexadecanoic acid, heptadecanoic acid, octadecanoic acid,
nanodecanoic acid, icosanoic acid, docosanoic acid, and
tetradocosanoic acid. Preferred of these are pentadecanoic acid,
hexadecanoic acid, and heptadecanoic acid. It is preferred that
these saturated fatty acids should have a linear structure.
[0052] Incidentally, dextrin is a saccharide formed by polymerizing
a plurality of .alpha.-glucose molecules through glycoside bonds,
and is generally obtained by hydrolyzing a starch. Inulin also is a
polysaccharide, and is designated as CAS No. 9005-8-5.
Consequently, these substances exert no influence on the
environment.
[0053] The amount of the thickener is not limited so long as the
saturated fatty acid triglyceride can be thickened thereby, and the
amount thereof can be suitably set in accordance with the desired
worked consistency, torque, etc. However, the amount thereof is
preferably 10-40% by mass based on the whole grease.
[0054] In the case where a grease composition is to be produced, it
is also possible to use a saturated fatty acid triglyceride as a
base oil and either magnesium stearate or calcium stearate as a
thickener. It is preferred that the magnesium stearate and the
calcium stearate to be used each should be of a food additive or
medicine additive grade which meets standards such as the Japanese
Standards for Food Additives or the Japanese Pharmacopoeia.
[0055] The content of the magnesium stearate or calcium stearate in
the grease composition is not particularly limited. However, the
content thereof is preferably 12-35% by mass. So long as the
content thereof is within that range, the grease composition, when
applied to a rolling device, can be inhibited from leaking out from
the sliding part or rolling part. As a result, the rolling device
can be lubricated over a long period. In case where the content
thereof is less than 12% by mass, this grease composition has
reduced shear stability and, hence, there is the possibility that
this grease composition, when applied to a rolling device, might be
softened by shearing in the sliding part or rolling part to
accelerate the leakage of the grease composition from the sliding
part or rolling part. As a result, there is the possibility that
the rolling device cannot be lubricated over a long period. On the
other hand, in case where the content of the thickener exceeds 35%
by mass, the proportion of the base oil in the grease composition
is low and, hence, there is the possibility that this grease
composition might have insufficient lubricity. From the standpoint
of inhibiting such troubles from occurring, the content of the
thickener in the grease composition is more preferably 12-28% by
mass, even more preferably 12-25% by mass, most preferably 15-25%
by mass.
[0056] Additives which are in general use in lubricants may be
further added to the lubricant composition in order to further
improve the various performances of the lubricant composition.
Examples thereof include rust preventives, extreme-pressure agents,
friction regulators, pH regulators, antiwear agents, oiliness
improvers, and metal deactivators. However, additives which contain
a metallic element are undesirable from the standpoint of the
environment. One of those additives may be used alone, or a
suitable combination of two or more thereof may be used. The total
content of the additives in the lubricant composition is not
particularly limited unless the additives defeat the objects of the
invention.
(Rolling Device)
[0057] The rolling device of the invention is lubricated with the
lubricant composition or grease composition described above. There
are no limitations on the kind of the rolling device. Examples
thereof include deep-groove ball bearings such as that shown in
FIG. 1. The deep-groove ball bearing shown in the figure is
equipped with: an inner ring 1 which has a raceway surface 1a in
the outer circumferential surface thereof; an outer ring 2 which
has, in the inner circumferential surface thereof, a raceway
surface 2a that faces the raceway surface la and which has been
disposed radially outside the inner ring 1; a plurality of rolling
elements (balls) 3 which have been disposed between the two raceway
surfaces 1a and 2a so as to be freely rollable; a cage 4 which
holds the multiple rolling elements 3 between the inner ring 1 and
the outer ring 2; and sealing devices 5 and 5 which serve as seals
that close the space openings present between the inner ring 1 and
the outer ring 2. Incidentally, the cage 4 and the sealing devices
5 may be omitted.
[0058] The grease composition described above is filled into the
space (bearing space) which has been formed between the inner ring
1 and the outer ring 2 and in which the rolling elements 3 have
been disposed, in order to lubricate between each raceway surface
1a or 2a and the rolling elements 3. Consequently, the rolling
device of the invention has excellent durability and exerts little
influence on the environment.
[0059] Incidentally, the embodiment shown is a mere example of the
invention, and the invention should not be construed as being
limited to the embodiment. For example, the invention can be
applied to other rolling bearings of various kinds The invention is
applicable to radial rolling bearings such as angular ball
bearings, self-aligning ball bearings, cylindrical roller bearings,
tapered roller bearings, needle roller bearings, and self-aligning
roller bearings and thrust rolling bearings such as thrust ball
bearings and thrust roller bearings. Applications of the invention
are not limited to such rolling bearings, and the invention is
further applicable to other rolling devices of various kinds, such
as, for example, ball screws, direct-acting guides, and
direct-acting bearings.
EXAMPLES
[0060] The invention will be further explained below by reference
to Examples and Comparative Examples. However, the invention should
not be construed as being limited by the Examples.
Example A
(Test 1: Examples 1A to 3A and Comparative Examples 1A to 19A)
[0061] Thioctic acid (.alpha.-LI), d-.alpha.-tocopherol (V.E.),
catechin (Kat), dibutylhydroxytoluene (BHT), isoflavone (IF),
.beta.-carotene (Car), and butylhydroxyanisole (BHA) were added
alone or in combination as shown in Table 1 to a saturated
medium-chain fatty acid triglyceride ("Panasate 875", manufactured
by NOF Corp.) to prepare test lubricating oils. The addition
amounts of those antioxidants were as follows. When an antioxidant
compound was used alone, the compound was added in an amount of
2.5% by mass. When a mixture of two antioxidant compounds was used,
each compound was added in an amount of 1.25% by mass, the total
amount thereof being 2.5% by mass.
TABLE-US-00001 TABLE 1 Example 1A Example 2A Example 3A .alpha.-LI
.alpha.-LI .alpha.-LI V.E. Kat Comparative Comparative Comparative
Comparative Example 1A Example 2A Example 3A Example 4A BHT V.E. IF
Kat BHT BHT BHT Comparative Comparative Comparative Comparative
Example 5A Example 6A Example 7A Example 8A Car BHA V.E. IF BHT BHT
V.E. Comparative Comparative Comparative Comparative Example 9A
Example 10A Example 11A Example 12A Car BHA IF Car V.E. V.E. IF
Comparative Comparative Comparative Comparative Example 13A Example
14A Example 15A Example 16A BHA Kat Car BHA IF Kat Kat Comparative
Comparative Comparative Example 17A Example 18A Example 19A Car BHA
BHA Car BHT: dibutylhydroxytoluene V.E.: d-.alpha.-tocopherol IF:
isoflavone Kat: catechin Car: .beta.-carotene .alpha.-LI: thioctic
acid BHA: butylhydroxyanisole
[0062] Forty grams of each test lubricating oil was placed on a
stainless-steel petri dish and heated in a 160.degree. C. oven. The
viscosity of the test lubricating oil was measured after a given
period had passed, and the increase in viscosity from the value
measured before the heating was determined. The results thereof are
shown in FIG. 2. The test lubricating oils of Examples 1A to 3A
contained thioctic acid alone or contained a mixture of thioctic
acid with catechin or d-.alpha.-tocopherol. It can be seen that
these lubricating oils were inhibited from suffering an increase in
viscosity due to heating.
(Test 2: Examples 4A to 8A and Comparative Examples 20A to 23A)
[0063] Thioctic acid, catechin, d-.alpha.-tocopherol,
butylhydroxyanisole (BHA), dibutylhydroxytoluene (BHT), or
phenyl-.alpha.-naphthylamine (PAN) was added to base greases each
including both a base oil and a thickener, as shown in Table 2, to
prepare test greases. As the base oil was used a saturated
medium-chain fatty acid triglyceride (MCT) or a polyol ester oil.
As the thickener, use was made of dextrin hexadecanoate, lithium
12-hydroxystearate, or a product of reaction between stearylamine
and 4,4'-diphenylmethane diisocyanate (C18-MDI urea). The amounts
of the thickeners in the base greases were 15% by mass for dextrin
hexadecanoate, 12% by mass for lithium 12-hydroxystearate, and 15%
by mass for the urea. Thus, the base greases had been regulated so
as to have the shown consistency values.
TABLE-US-00002 TABLE 2 Kind Viscosity of of base oil Consistency
Base Thickener (mm.sup.2/s, at 40.degree. C.) unworked worked oil
Composition of additive Example 4A dextrin 12.8 248 290 MCT
thioctic acid, 2.5 mass % hexadecanoate Example 5A dextrin 12.8 262
290 MCT thioctic acid, 1.25 mass % + hexadecanoate catechin, 1.25
mass % Example 6A dextrin 12.8 262 292 MCT thioctic acid, 1.25 mass
% + hexadecanoate d-.alpha.-tocopherol, 1.25 mass % Example 7A
lithium 32.0 252 264 polyol thioctic acid, 1.25 mass % +
12-hydroxystearate ester catechin, 1.25 mass % Example 8A C18-MDI
urea 32.0 252 274 polyol thioctic acid, 1.25 mass % + ester
catechin, 1.25 mass % Comparative dextrin 12.8 255 286 MCT BHA, 2.5
mass % Example 20A hexadecanoate Comparative dextrin 12.8 258 290
MCT BHA, 1.25 mass % + Example 21A hexadecanoate BHT, 1.25 mass %
Comparative lithium 32.0 256 268 polyol BHT, 1.25 mass % + Example
22A 12-hydroxystearate ester PAN, 1.25 mass % Comparative C18-MDI
urea 32.0 250 270 polyol BHT, 1.25 mass % + Example 23A ester PAN,
1.25 mass % C18-MDI urea: product of reaction between stearylamine
and 4,4'-diphenylmethane diisocyanate MCT: saturated middle-chain
fatty acid triglyceride BHA: butylhydroxyanisole BHT:
dibutylhydroxytoluene PAN: phenyl-.alpha.-naphthylamine
[0064] Thereafter, 3.4 g of each test grease was enclosed in
bearing "6305VVC3E", manufactured by NSK Ltd., and the bearing was
rotated under the conditions 1 and conditions 2 shown in Table 3 to
determine the life. This test was conducted twice under each set of
conditions.
TABLE-US-00003 TABLE 3 Rotation Grease Ambient Axial speed amount
temperature Bearing load (N) (rpm) (g) (.degree. C.) Conditions 1
6305VVC3E 198 15,000 3.4 80 Conditions 2 6305VVC3E 198 10,000 3.4
120
[0065] The results obtained under the conditions 1 are shown in
FIG. 3, and the results obtained under the conditions 2 are shown
in FIG. 4. It can be seen that the addition of thioctic acid alone
or a mixture of thioctic acid and either catechin or
d-.alpha.-tocopherol enhanced high-temperature durability and
resulted in a prolongation of life, as in Examples 4A to 8A. In
particular, as shown in FIG. 4, these antioxidants even at the high
temperature showed a higher oxidation-preventing effect and brought
about longer lives than the phenol/amine combination, which has
conventionally been used as an industrial additive. Furthermore,
such performance of the antioxidants according to the invention
changed little when the base oil or the thickener changed.
Example B
[0066] Test greases were prepared in accordance with the formations
shown in
[0067] Table 4.
TABLE-US-00004 TABLE 4 Worked Unworked Consis- Consis- Thickener
Base oil Antioxidant tency tency Example 1B aluminum complex soap
MCT dl-.alpha.-tocopherol 292 262 Example 2B dextrin palmitate MCT
d-.alpha.-tocopherol 286 260 Example 3B dextrin palmitate MCT
d-.alpha.-tocopherol + 286 258 d-.delta.-tocopherol Example 4B urea
compound MCT d-.delta.-tocopherol 198 178 Comparative lithium
polyol ester oil dl-.alpha.-tocopherol 187 174 Example 1B
12-hydroxystearate Comparative aluminum complex soap MCT
dl-.alpha.-tocopherol 289 258 Example 2B Comparative dextrin
palmitate MCT d-.alpha.-tocopherol 291 266 Example 3B Comparative
dextrin palmitate MCT d-.alpha.-tocopherol + 286 248 Example 4B
d-.delta.-tocopherol Comparative urea compound MCT
d-.delta.-tocopherol 198 178 Example 5B Comparative dextrin
palmitate rapeseed oil d-.delta.-tocopherol 250 230 Example 6B
Comparative dextrin palmitate rapeseed oil d-.alpha.-tocopherol +
248 225 Example 7B d-.delta.-tocopherol
[0068] The grease of Example 1B was a grease which included a
medium-chain fatty acid triglyceride (MCT) having a dynamic
viscosity at 40.degree. C. of 12.8 mPas as a base oil and an
aluminum complex soap as a thickener, and which had been obtained
by adding an antioxidant and coenzyme Q10 to the base oil and
thickener in an amount of 2.5% by mass each. The kind of the
antioxidant added was dl-.alpha.-tocopherol as shown in Table
4.
[0069] The grease of Example 2B was a grease which included a
medium-chain fatty acid triglyceride (MCT) having a dynamic
viscosity at 40.degree. C. of 12.8 mPas as a base oil and dextrin
palmitate as a thickener, and which had been obtained by adding an
antioxidant and coenzyme Q10 to the base oil and thickener in an
amount of 2.5% by mass each. The kind of the antioxidant added was
d-.alpha.-tocopherol as shown in Table 4.
[0070] The grease of Example 3B was a grease which included a
medium-chain fatty acid triglyceride (MCT) having a dynamic
viscosity at 40.degree. C. of 12.8 mPas as a base oil and dextrin
palmitate as a thickener, and which had been obtained by adding an
antioxidant and coenzyme Q10 to the base oil and thickener in an
amount of 2.5% by mass each. The kind of the antioxidant added was
a natural type vitamin E which was on the market as a mixture of
d-.alpha.-tocopherol and d-.delta.-tocopherol, as shown in Table
4.
[0071] The grease of Example 4B was a grease which included a
medium-chain fatty acid triglyceride (MCT) having a dynamic
viscosity at 40.degree. C. of 12.8 mPas as a base oil and a urea
compound as a thickener, and which had been obtained by adding an
antioxidant and coenzyme Q10 to the base oil and thickener in an
amount of 2.5% by mass each. The kind of the antioxidant added was
d-.delta.-tocopherol as shown in Table 4. The urea compound was a
compound synthesized by reacting 1 mol of diphenylmethane
4,4'-diisocyanate (MDI) with 2 mol of stearylamine.
[0072] Incidentally, the amount of the thickener added in each of
Examples 1B to 4B was 12% by mass. The values of worked consistency
and unworked consistency of these test greases were as shown in
Table 4.
[0073] The grease of Comparative Example 1B was a grease which
included a polyol ester oil having a dynamic viscosity at
40.degree. C. of 32.6 mPas as a base oil and lithium
12-hydroxystearate as a thickener, and which had been obtained by
adding an antioxidant to the base oil and thickener in an amount of
5% by mass. The kind of the antioxidant added was
dl-.alpha.-tocopherol as shown in Table 4.
[0074] The grease of Comparative Example 2B was a grease which
included a medium-chain fatty acid triglyceride (MCT) having a
dynamic viscosity at 40.degree. C. of 12.8 mPas as a base oil and
an aluminum complex soap as a thickener, and which had been
obtained by adding an antioxidant to the base oil and thickener in
an amount of 5% by mass. The kind of the antioxidant added was
dl-.alpha.-tocopherol as shown in Table 4.
[0075] The grease of Comparative Example 3B was a grease which
included a medium-chain fatty acid triglyceride (MCT) having a
dynamic viscosity at 40.degree. C. of 12.8 mPas as a base oil and
dextrin palmitate as a thickener, and which had been obtained by
adding an antioxidant to the base oil and thickener in an amount of
5% by mass. The kind of the antioxidant added was
d-.alpha.-tocopherol as shown in Table 4.
[0076] The grease of Comparative Example 4B was a grease which
included a medium-chain fatty acid triglyceride (MCT) having a
dynamic viscosity at 40.degree. C. of 12.8 mPas as a base oil and
dextrin palmitate as a thickener, and which had been obtained by
adding an antioxidant to the base oil and thickener in an amount of
5% by mass. The kind of the antioxidant added was a natural type
vitamin E which was on the market as a mixture of
d-.alpha.-tocopherol and d-.delta.-tocopherol, as shown in Table
4.
[0077] The grease of Comparative Example 5B was a grease which
included a medium-chain fatty acid triglyceride (MCT) having a
dynamic viscosity at 40.degree. C. of 12.8 mPas as a base oil and
dextrin palmitate as a thickener, and which had been obtained by
adding an antioxidant to the base oil and thickener in an amount of
5% by mass. The kind of the antioxidant added was
d-.delta.-tocopherol as shown in Table 4. The urea compound was a
compound synthesized by reacting 1 mol of diphenylmethane
4,4'-diisocyanate (MDI) with 2 mol of stearylamine.
[0078] The grease of Comparative Example 6B was a grease which
included rapeseed oil having a dynamic viscosity at 40.degree. C.
of 32 mPas as a base oil and dextrin palmitate as a thickener, and
which had been obtained by adding an antioxidant to the base oil
and thickener in an amount of 5% by mass. The kind of the
antioxidant added was d-.delta.-tocopherol as shown in Table 4.
[0079] The grease of Comparative Example 7B was a grease which
included rapeseed oil having a dynamic viscosity at 40.degree. C.
of 32 mPas as a base oil and dextrin palmitate as a thickener, and
which had been obtained by adding an antioxidant to the base oil
and thickener in an amount of 5% by mass. The kind of the
antioxidant added was a natural type vitamin E which was on the
market as a mixture of d-.alpha.-tocopherol and
d-.delta.-tocopherol, as shown in Table 4.
[0080] Incidentally, the amount of the thickener added in each of
Comparative Examples 1B to 7B was 12% by mass. The values of worked
consistency and unworked consistency of these test greases were as
shown in Table 4. Comparative Examples 2B, 3B, 4B, and 5B are
Reference Examples for ascertaining the effect of the coenzyme
Q.
[Life Test]
[0081] With respect to the test greases of Example 1B and
Comparative Examples 1B and 2B, 3.4 g of each test grease was
enclosed in rolling bearing No. 6305VVC3E, and this rolling bearing
was rotated under the conditions of an ambient temperature of
120.degree. C., an axial load of 98 N, and a rotation speed of
10,000 min.sup.-1. The period required for the driving motor for
rotating the rolling bearing to stop due to overload was measured,
and this period was taken as the life.
[0082] With respect to the test greases of Examples 2B to 4B and
Comparative Examples 3B to 5B, 1.0 g of each test grease was
enclosed in rolling bearing No. 6303VVC3E, and this rolling bearing
was rotated under the conditions of an ambient temperature of
80.degree. C., a radial load of 198 N, and a rotation speed of
24,000 min.sup.-1. The period required for the driving motor for
rotating the rolling bearing to stop due to overload was measured,
and this period was taken as the life.
[0083] Furthermore, with respect to the test greases of Comparative
Examples 6B and 7B, 1.0 g of each test grease was enclosed in
rolling bearing No. 6303VVC3E, and this rolling bearing was rotated
under the conditions of an ambient temperature of 80.degree. C., a
radial load of 198 N, and a rotation speed of 24,000 min.sup.-1.
The period required for the driving motor for rotating the rolling
bearing to stop due to overload was measured, and this period was
taken as the life.
[0084] Incidentally, the life test was conducted twice for each
test grease. The results thereof are shown as graphs in FIGS. 5 to
7. As can be seen from the graphs given in FIGS. 5 to 7, the
Examples, in which the test greases each contained coenzyme Q10,
attained a longer life than the Comparative Examples, in which the
test greases did not contain coenzyme Q10.
Example C
Example 1C
[0085] Eighty-five grams of a saturated medium-chain fatty acid
triglyceride having a dynamic viscosity at 40.degree. C. of 14.8
mm.sup.2/s (Panasate 875, manufactured by NOF Corp.) was mixed with
15 g of magnesium stearate, and this mixture was heated, with
stirring, to a temperature at which the magnesium stearate
dissolved. After the magnesium stearate had dissolved completely,
the solution was poured into an aluminum vat which had been cooled
beforehand. This vat was cooled with flowing water. The mixture
which had become greasy was kneaded with a three-roll mill to
obtain a test grease. This test grease had a value of worked
consistency of 300.
Comparative Example 1C
[0086] Eighty-eight grams of a saturated medium-chain fatty acid
triglyceride having a dynamic viscosity at 40.degree. C. of 14.8
mm.sup.2/s (Panasate 875, manufactured by NOF Corp.) was mixed with
12 g of lithium 12-hydroxystearate, and this mixture was heated,
with stirring, to a temperature at which the lithium
12-hydroxystearate dissolved. After the lithium 12-hydroxystearate
had dissolved completely, the solution was poured into an aluminum
vat which had been cooled beforehand. This vat was cooled with
flowing water. The mixture which had become greasy was kneaded with
a three-roll mill to obtain a test grease. This test grease had a
value of worked consistency of 231.
Comparative Example 2C
[0087] Eighty-eight grams of a polyol ester oil having a dynamic
viscosity at 40.degree. C. of 26.0 mm.sup.2/s was mixed with 12 g
of lithium 12-hydroxystearate, and this mixture was heated, with
stirring, to a temperature at which the lithium 12-hydroxystearate
dissolved. After the lithium 12-hydroxystearate had dissolved
completely, the solution was poured into an aluminum vat which had
been cooled beforehand. This vat was cooled with flowing water. The
mixture which had become greasy was kneaded with a three-roll mill
to obtain a test grease. This test grease had a value of worked
consistency of 250.
[Rotation Torque Test]
[0088] Each of the test greases thus produced was filled, in an
amount of 1.0 g, into the bearing space of deep-groove ball bearing
No. 6203VV (inner diameter, 17 mm; outer diameter, 40 mm). Thus,
three test bearings were obtained. These test bearings were
subjected to a rotation test at various rotation speeds
(1,800-7,500 min.sup.-1) and examined for rotation torque. The
axial load was set at 196 N, and the test temperature was room
temperature.
[0089] The rotation torque was measured throughout the period from
the time when 550 seconds had passed since the initiation of
rotation to the time when 600 seconds had passed since the rotation
initiation, and the average value thereof was taken as the rotation
torque of this test bearing. The results thereof are shown as a
graph in FIG. 8. The abscissa of the graph in FIG. 8 is the value
of dmN determined from the rotation speed during the test. As can
be seen from the graph given in FIG. 8, the test bearing equipped
with the test grease of Example 1C showed excellent low-torque
characteristics at each rotation speed as compared with the test
bearings equipped with the test greases of Comparative Examples 1C
and 2C.
Example D
Example 1D
[0090] Eighty-five grams of a saturated medium-chain fatty acid
triglyceride having a dynamic viscosity at 40.degree. C. of 14.8
mm.sup.2/s (Panasate 875, manufactured by NOF Corp.) was mixed with
15 g of calcium stearate, and this mixture was heated, with
stirring, to a temperature at which the calcium stearate dissolved.
After the calcium stearate had dissolved completely, the solution
was poured into an aluminum vat which had been cooled beforehand.
This vat was cooled with flowing water. The mixture which had
become greasy was kneaded with a three-roll mill to obtain a test
grease. This test grease had a value of worked consistency of
230.
Comparative Example 1D
[0091] Eighty-eight grams of a saturated medium-chain fatty acid
triglyceride having a dynamic viscosity at 40.degree. C. of 14.8
mm.sup.2/s (Panasate 875, manufactured by NOF Corp.) was mixed with
12 g of lithium 12-hydroxystearate, and this mixture was heated,
with stirring, to a temperature at which the lithium
12-hydroxystearate dissolved. After the lithium 12-hydroxystearate
had dissolved completely, the solution was poured into an aluminum
vat which had been cooled beforehand. This vat was cooled with
flowing water. The mixture which had become greasy was kneaded with
a three-roll mill to obtain a test grease. This test grease had a
value of worked consistency of 231.
Comparative Example 2D
[0092] Eighty-eight grams of a polyol ester oil having a dynamic
viscosity at 40.degree. C. of 26.0 mm.sup.2/s was mixed with 12 g
of lithium 12-hydroxystearate, and this mixture was heated, with
stirring, to a temperature at which the lithium 12-hydroxystearate
dissolved. After the lithium 12-hydroxystearate had dissolved
completely, the solution was poured into an aluminum vat which had
been cooled beforehand. This vat was cooled with flowing water. The
mixture which had become greasy was kneaded with a three-roll mill
to obtain a test grease. This test grease had a value of worked
consistency of 250.
[Rotation Torque Test]
[0093] A rotation torque test was conducted in the same manner as
in Example C. The results thereof are shown as a graph in FIG. 9.
The abscissa of the graph in FIG. 9 is the value of dmN determined
from the rotation speed during the test. As can be seen from the
graph given in FIG. 9, the test bearing equipped with the test
grease of Example 1D showed excellent low-torque characteristics at
each rotation speed as compared with the test bearings equipped
with the test greases of Comparative Examples 1D and 2D.
[0094] While the invention has been described in detail and with
reference to specific embodiments thereof, it will be apparent to
one skilled in the art that various changes and modifications can
be made therein without departing from the spirit and scope
thereof.
[0095] This application is based on a Japanese patent application
filed on Jun. 15, 2011 (Application No. 2011-133118), a Japanese
patent application filed on Nov. 30, 2011 (Application No.
2011-262944), and a Japanese patent application filed on Nov. 30,
2011 (Application No. 2011-262945), the contents thereof being
incorporated herein by reference.
INDUSTRIAL APPLICABILITY
[0096] The lubricant compositions and rolling device of the
invention are useful in or as the rotating parts or sliding parts
of various machines and apparatus. The lubricant compositions are
harmless even when eaten, and impose little burden on the
environment. Consequently, the lubricant compositions and the
rolling device are useful especially in machines and apparatus
which relate to foods or medical supplies.
DESCRIPTION OF REFERENCE NUMERALS AND SIGNS
[0097] 1 Inner ring [0098] 1a Raceway surface [0099] 2 Outer ring
[0100] 2a Raceway surface [0101] 3 Rolling element [0102] G
Lubricant composition
* * * * *