U.S. patent application number 10/377964 was filed with the patent office on 2003-11-27 for low noise synthetic resin composition and method.
This patent application is currently assigned to Minebea, Co., Ltd.. Invention is credited to Akiyama, Motoharu, Hokkirigawa, Kazuo, Kawamura, Morinobu.
Application Number | 20030220421 10/377964 |
Document ID | / |
Family ID | 27767965 |
Filed Date | 2003-11-27 |
United States Patent
Application |
20030220421 |
Kind Code |
A1 |
Hokkirigawa, Kazuo ; et
al. |
November 27, 2003 |
Low noise synthetic resin composition and method
Abstract
A low noise composition includes fine particles of RBC or CRBC
dispersed in a synthetic resin. The composition can be formed into
an article of manufacture prepared by molding the composition.
Inventors: |
Hokkirigawa, Kazuo;
(Sendai-Shi, JP) ; Akiyama, Motoharu; (Nagano-Ken,
JP) ; Kawamura, Morinobu; (Nagano-Ken, JP) |
Correspondence
Address: |
OSTROLENK FABER GERB & SOFFEN
1180 AVENUE OF THE AMERICAS
NEW YORK
NY
100368403
|
Assignee: |
Minebea, Co., Ltd.
|
Family ID: |
27767965 |
Appl. No.: |
10/377964 |
Filed: |
February 28, 2003 |
Current U.S.
Class: |
524/9 |
Current CPC
Class: |
F16C 17/14 20130101;
C08K 3/04 20130101; Y10S 384/907 20130101; F16C 33/043 20130101;
F16C 33/201 20130101 |
Class at
Publication: |
524/9 |
International
Class: |
C08K 011/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 1, 2002 |
JP |
2002-055307 |
Mar 1, 2002 |
JP |
2002-055308 |
Mar 7, 2002 |
JP |
2002-062412 |
Mar 7, 2002 |
JP |
2002-062406 |
Jun 17, 2002 |
JP |
2002-176436 |
Sep 18, 2002 |
JP |
2002-272147 |
Claims
What is claimed is:
1. An article of manufacture, comprising: a molded low noise resin
composition including particles of at least one of RBC and CRBC
dispersed in a resin.
2. The article of manufacture of claim 1, wherein the particles are
uniformly dispersed in the resin.
3. The article of manufacture of claim 1, wherein the composition
includes about 30-70% by weight of the at least one of RBC and
CRBC.
4. The article of manufacture of claim 1, wherein the weight ratio
of the fine particles of the at least one of RBC and CRBC to the
resin is about 30 to 90:70 to 10.
5. The article of manufacture of claim 1, wherein the particles
include a powder.
6. The article of manufacture of claim 1, wherein the resin is a
thermoplastic resin selected from the group consisting of at least
one of: polyacetal, polyamide, polyester, and polyolefins.
7. The article of manufacture of claim 6, wherein the thermoplastic
resin is selected from the group consisting of at least one of:
polyacetal, nylon 66, nylon 6, nylon 11, nylon 12, polybutylene
terephthalate, polyethylene terephthalate, polypropylene, and
polyethylene.
8. The article of manufacture of claim 1, wherein the mean particle
size of the particles of the at least one of RBC and CRBC is about
300 .mu.m or less.
9. The article of manufacture of claim 7, wherein the mean particle
size of the particles of the at least one of RBC and CRBC is about
20 to 150 .mu.m.
10. The article of manufacture of claim 1, further comprising
fibers selected from the group consisting of at least one of:
inorganic fibers, synthetic fibers, and natural pulp fibers.
11. The article of manufacture of claim 1, wherein the article is
molded into a form selected from the group consisting of at least
one of: screws, axial relays, cam mechanisms, cylinders, pistons,
wheels, friction wheels, belts, pulleys, chains, sprockets, valves,
and tubes.
12. An article of manufacture, comprising: a body having a low
friction contact surface, at least part of the body being formed
from a composite material including, fine particles of at least one
of RBC and CRBC; and a resin material, wherein the fine particles
are dispersed within the resin material.
13. The article of manufacture of claim 12, wherein the fine
particles are uniformly dispersed in the resin material.
14. The article of manufacture of claim 12, wherein the body
includes at least one of a screw, an axial relay, a cam mechanism,
a cylinder, a piston, a wheel, a friction wheel, a belt, a pulley,
a chain, a sprocket, a valve, and a tube.
15. The article of manufacture of claim 12, wherein the composite
material includes about 30-70% by weight of the at least one of RBC
and CRBC.
16. The article of manufacture of claim 12, wherein the weight
ratio of the fine particles to the resin material is about 30 to
90:70 to 10.
17. The article of manufacture of claim 12, wherein the resin
material is a thermoplastic resin.
18. The article of manufacture of claim 17, wherein the resin is
selected from the group consisting of at least one of: polyacetal,
polyamide, polyester, polyolefins.
19. The article of manufacture of claim 18, wherein the resin is
selected from the group consisting of at least one of: polyacetal,
nylon 66, nylon 6, nylon 11, nylon 12, polybutylene terephthalate,
polyethylene terephthalate, polypropylene, and polyethylene.
20. The article of manufacture of claim 12, wherein the mean
particle size of the fine particles is about 300 .mu.m or less.
21. The article of manufacture of claim 20, wherein the mean
particle size of the fine particles is about 20 to 150 .mu.m.
22. The article of manufacture of claim 12, further comprising
fibers selected from the group consisting of at least one of:
inorganic fibers, synthetic fibers, and natural pulp fibers.
23. The article of manufacture of claim 22, wherein the synthetic
fibers are selected from the group consisting of at least one of:
polyester, rayon, polyvinyl alcohol, polyamide, polyolefin and
acrylic.
24. The article of manufacture of claim 22, wherein the natural
pulp fibers are selected from the group consisting of: wood pulp
and Manila hemp.
25. The article of manufacture of claim 17, wherein the resin
material includes a thermosetting resin.
26. The article of manufacture of claim 25, wherein the
thermosetting resin is selected from the group consisting of at
least one of: phenolics, diaryl phthalate resins, unsaturated
polyester resins, epoxies, polyimides, and a triazine resins
system.
27. An apparatus, comprising: a component, wherein the component
has a low noise contact surface, and at least part of the component
is formed of a composite including a resin and about 30-70% by
weight of at least one of RBC and CRBC, wherein the at least one of
RBC and CRBC is uniformly dispersed in the resin.
28. The apparatus of claim 27, wherein the mean particle size of
the at least one of RBC and CRBC is about 300 .mu.m or less.
29. The apparatus of claim 28, wherein the mean particle size is
about 20 to 150 .mu.m.
30. The apparatus of claim 27, wherein the component is at least
one of a screw, an axial relay, a cam mechanism, a cylinder, a
piston, a wheel, a friction wheel, a belt, a pulley, a chain, a
sprocket, a valve, and a tube.
31. A method for manufacturing low noise machinery parts,
comprising the steps of: a) providing fine particles of at least
one of RBC and CRBC; b) providing at least one resin material; c)
mixing the fine particles with the at least one resin material to
obtain a mixture; and d) forming at least one part of an article
from the mixture, wherein the at least part of the article includes
a composite material having the fine particles dispersed within the
resin material.
32. The method of claim 31, wherein the mixture is heated before
forming the article.
33. The method of claim 31, wherein the article is formed by
molding.
34. The method of claim 31, wherein the article is formed by one of
extrusion molding and injection molding.
35. The method of claim 31, wherein the molding takes place at a
temperature between the glass transition temperature and the
melting temperature of the at least one resin material.
36. The method of claim 31, further comprising the step of: cooling
the article gradually.
37. The method of claim 31, wherein the fine particles are
uniformly dispersed within the at least one resin material.
38. The method of claim 31, wherein the article is one of a screw,
an axial relay, a cam mechanism, a cylinder, a piston, a wheel, a
friction wheel, a belt, a pulley, a chain, a sprocket, a valve, and
a tube.
39. The method of claim 31, wherein the weight ratio of the fine
particles to the resin material is about 30 to 90:70 to 10.
40. The method of claim 31, wherein the resin material is a
thermoplastic resin.
41. The method of claim 40, wherein the resin is selected from the
group consisting of at least one of: polyacetal, nylon 66, nylon 6,
nylon 11, nylon 12, polybutylene terephthalate, polyethylene
terephthalate, polypropylene, and polyethylene.
42. The method of claim 31, wherein the mean particle size of the
fine particles is about 300 .mu.m or less.
43. The method of claim 42, wherein the mean particle size of the
fine particles is about 20 to 150 .mu.m.
44. The method of claim 31, further comprising the step of: adding
at least fiber selected from the group consisting of at least one
of: inorganic fibers, synthetic fibers, and natural pulp fibers to
the mixture of the fine particles and the resin material.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to synthetic resin
compositions. More particularly, the present invention relates to
synthetic resin compositions that can be molded into articles that
generate less noise in use.
[0003] 2. Description of the Related Art
[0004] In the fields of office automation ("OA") machines,
automobile parts, and machinery, there has been progress in the use
of resin for parts such as wheels, cams, and bearings by employing
engineering plastics, such as polyacetal and the like. The use of
these resins has greatly contributed to reducing the manufacturing
costs of articles produced from them.
[0005] Unfortunately, in many cases, particularly where the molded
parts are required to slide against other parts during use, noise
is generated. Attempts have been made to reduce this high noise
level by reducing the modulus of elasticity of the resin itself,
for example, by applying grease to the resin. This solution,
however, has been unsatisfactory. It has been found that the
applied grease can, in use, spatter to the surrounding mechanisms,
adversely affecting their physical properties. In addition, other
problems may arise, such as an increase in torque, a reduction in
strength, and a general lowering of efficiency.
[0006] Another cause of noise in engineering plastics is the
"stick-slip phenomenon."When one surface is pressed against another
surface with a normal force, n, and another force is applied that
causes the one surface to slide across another surface, a drag
force can be measured that is parallel to the surfaces and in a
direction opposite to the applied force. This kinetic drag force,
f.sub.k, is called a dynamic friction force or kinetic friction
force and is related to the magnitude of the normal force by a
dynamic friction coefficient, .mu..sub.D(v.sub.s). The dynamic
friction coefficient, .mu..sub.D(v.sub.s), depends upon the sliding
speed, v.sub.s, and the surface characteristics of each of the
materials in contact with each other. If .mu..sub.D is known for a
particular v.sub.s, then the dynamic friction coefficient is
determined by the following formula: f.sub.k=.mu..sub.D.multidot.n,
where f.sub.k is the dynamic friction force and n is the normal
force pressing the surfaces together. Thus, .mu..sub.D may be
measured by determining the ratio f.sub.k/n.
[0007] Generally, the dynamic friction force and the coefficient of
dynamic friction approach a constant value as the sliding speed,
v.sub.s, approaches a high velocity, for example greater than 1
meter per second (m/s). Thus, at high velocities the coefficient of
dynamic friction is independent of the sliding speed, v.sub.s.
However, at low sliding speed, v.sub.s, the coefficient of dynamic
friction, .mu..sub.D, is speed dependent. Typically, the dynamic
friction force, f.sub.k, approaches a maximum as the sliding speed,
v.sub.s, approaches 0. When the sliding speed, v.sub.s, is 0, then
the two surfaces are at rest with each other, and the measured
friction force is defined as a static friction force. The maximum
static friction force, f.sub.max, occurs immediately prior to the
onset of sliding. A large difference between the maximum static
friction force, f.sub.max, at v.sub.s=0 and the dynamic static
force at a high sliding speed, f.sub.k(v.sub.s=.infin.), results in
stick-slip behavior. A large difference between f.sub.max and
f.sub.k(v.sub.2=.infin.) results in stick-slip behavior that causes
excessive noise in mechanical devices that use the material. Thus,
it is desirable to have a material with little or no stick-slip
behavior.
[0008] The stick-slip phenomenon may be understood by a perusal of
FIGS. 1 and 2 which show a device used for placing a certain load W
at a tip 2' of a stick 2. Stick 2 is held by a bearing 4 in a
freely rotatable fashion on a disc 1 made of the testing material.
A spring 3 is fixed at the intermediate part of stick 2. Disk 1 is
rotated in the direction indicated by the arrow mark by means of a
driving device 5.
[0009] When the rotation of disk 1 is started by driving device 5,
stick 2 shifts from its static position A.sup.0 to A.sup.1 where a
balance is struck with spring 3, thereby achieving a stable state
because of the difference between the static friction coefficient
.mu..sub.S and the dynamic friction coefficient .mu..sub.D on the
contact surface between disk 1 and tip 2' of stick 2. Where the
difference between the static friction coefficient .mu..sub.S and
the dynamic friction coefficient .mu..sub.D is large, a strain
greater than the normal value is applied to spring 3, whereupon
A.sup.1 is exceeded and A.sup.2 is reached. The stick is then
displaced to position A.sup.-1 and brought back to A.sup.0 by the
restorative force of the spring.
[0010] If, in this state, disk 1 is caused to continue rotating,
stick 2 will repeat the same action between A.sup.-1, A.sup.0, and
A.sup.2. As a consequence, the stick will start vibrating, thereby
generating noise.
[0011] Thus, the stick-slip phenomenon is created by the difference
between the static friction coefficient .mu..sub.S and the dynamic
friction coefficient .mu..sub.D. When a resin composition having a
large difference is molded into a machine element, the stick slip
phenomenon is manifested as noise in a machine device using the
machine element.
[0012] Thus, there is a need for a resin composition that can be
molded into useful parts that inherently will produce little or no
noise in use.
SUMMARY OF THE INVENTION
[0013] The present invention relates to a synthetic resin
composition for preventing noise in finished parts molded from the
composition. The materials have a small difference between their
static friction coefficient, .mu..sub.S, and their dynamic friction
coefficient, .mu..sub.D. This substantially reduces the "stick-slip
phenomenon", which is the source of noise in engineering plastics,
such as polyacetal and the like.
[0014] More particularly, the present invention is directed to a
low noise composition comprising fine particles of RBC or CRBC
uniformly dispersed in a synthetic resin.
[0015] In an alternative embodiment, the present invention is
directed to an article of manufacture comprising a molded low noise
synthetic resin composition comprising fine particles of RBC or
CRBC uniformly dispersed in a synthetic resin.
[0016] Other features and advantages of the present invention will
become apparent from the following description of the preferred
embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is an oblique view of the equipment for measuring the
stick-slip phenomenon.
[0018] FIG. 2 is a cross section of the equipment for measuring the
stick-slip phenomenon.
[0019] FIG. 3 is a graph depicting the friction characteristics of
a polyacetal molded product ("RBC/POM").
[0020] FIG. 4 is a graph depicting the friction characteristics of
a polyamide (nylon 66) molded product ("RBC/PA66").
[0021] FIG. 5 is a graph depicting the friction characteristics of
a polyamide (nylon 66) molded product containing glass fibers
("RBC/GF23PA66").
[0022] FIG. 6 is a graph depicting the friction characteristics of
a polyamide (nylon 11) molded product ("CRBC/PA11").
[0023] FIG. 7 is a graph depicting the friction characteristics of
a polybutylene terephthalate molded product ("CRBC/PBT").
[0024] FIG. 8 is a graph depicting the friction characteristics of
a polypropylene molded product ("CRBC/PP").
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0025] In accordance with the present invention, fine particles of
a rice bran ceramic ("RBC") or a carbonized rice bran ceramic
("CRBC") are uniformly dispersed in a synthetic resin to provide a
low noise composition. RBC and CRBC are advantageous because they
possess the following qualities:
[0026] 1. they are very hard;
[0027] 2. when they are made into grains, their shape is
irregular;
[0028] 3. their expansion coefficient is extremely small;
[0029] 4. they are electrically conductive;
[0030] 5. their specific gravity is low and they are light and
porous;
[0031] 6. their friction coefficient is extremely small; and
[0032] 7. their resistance to friction is superior.
[0033] Moreover, because the materials are rice bran, there is no
adverse effect upon the earth's environment and they serve to
preserve natural resources.
[0034] To produce RBC or CRBC, rice bran is preferably used as a
starting material because of its low cost. Large quantities are
produced as a by-product of other processes, e.g., about 900,000
tons per year in Japan alone and 33,000,000 tons per year
throughout the world.
[0035] RBC is a carbon material made, for example, by mixing and
kneading a de-fatted rice bran (de-fatted bran obtained from rice)
with a thermally hardening or thermosetting resin, molding a
product from the mixture, drying it, and then firing the dried
molded product in an inert gas atmosphere, e.g., sintering. See
Kazuo Hokkirigawa, Kino Zairyo "Functional Materials", Vol. 17, No.
5, pp. 24-28 (May 1997).
[0036] Preferably, the thermosetting resin that is mixed with the
de-fatted rice bran should be any resin that is heat hardened or
cured by heating. Preferred resins include, but not limited to,
phenolics, diaryl phthalate resins, unsaturated polyester resins,
epoxies, polyimides, triazine resins and the like. Phenolic resins,
e.g., resols, are especially preferred.
[0037] The mixing ratio of de-fatted rice bran to the thermosetting
resin should be in the range from about 50 to 90:50 to 10 (about
50:50 to about 90:10) by weight. A ratio of about 75:25 is
especially preferred.
[0038] CRBC is a carbon material also obtained from defatted rice
bran and a thermosetting resin, bus is an improvement over RBC. To
prepare a CRBC, for example, the de-fatted rice bran and the
thermosetting resin are mixed, kneaded, and then first fired in an
inert gas atmosphere at a temperature in the range of about
700.degree. C. to 1000.degree. C., e.g., sintered. Ordinarily, the
mixture is fired in a rotary kiln for a period of about 40 to about
120 minutes. The resulting material is then pulverized (crushed)
into to less than about 100 mesh to form carbonized powder.
[0039] The carbonized powder is then mixed with a thermosetting
resin, which may be, but is not necessarily, the same as that
employed with the de-fatted rice bran, and kneaded. This product is
then molded under pressure in the range of about 20 Mpa to 30 Mpa.
The molded product is once again heat treated in an inert gas
atmosphere at a temperature in the range from about 100.degree. to
1100.degree. C., e.g., sintered, thereby obtaining a black resin or
porous CRBC ceramic.
[0040] According to the present invention, fine particles of RBC or
CRBC are mixed with a synthetic resin to form a synthetic resin
composite having unique and useful friction characteristics.
Preferably, the RBC or CRBC constitutes about 30-70% by weight of
the entire synthetic resin composite. Preferably, the weight ratio
of the RBC or CRBC particles to the synthetic resin is about 30 to
90:70 to 10 (about 30:70 to about 90:10).
[0041] In a preferred embodiment, the RBC or CRBC particles are
uniformly dispersed in a synthetic resin. The fine particles are
uniformly dispersed by mixing them with the synthetic resin at or
near the resin's fusion point, followed by kneading. As a result of
the uniform dispersal, and especially when the weight ratio of the
particles to the synthetic resin is about 30 to 90:70 to 10 (about
30:70 to about 90:10), the difference between the static friction
coefficient .mu..sub.S and the dynamic friction coefficient
.mu..sub.D on the surface of an article molded from the composition
is reduced.
[0042] In a preferred embodiment, the RBC or CRBC should have a
mean particle size of about 300 .mu.m or less, preferably a mean
particle size of about 20-150 .mu.m. It has been found that a
synthetic resin composite of the present invention including fine
particles of RBC or CRBC, results in a composition that has surface
characteristics that make the composition particularly suitable for
use in low noise applications.
[0043] Preferably, the synthetic resins that are mixed with the RBC
or CRBC are thermoplastic resins. Examples of these resins include,
but are not limited to, polyacetal, polyamide, polyester,
polyolefins, and the like. POM (polyacetal, i.e.,
polyoxymethylene), nylon 66 (polyhexamethylene adipamide), nylon 6
(polycapramide), nylon 11 (polyundecanamide), nylon 12,
polybutylene terephthalate, polyethylene teraphthalate,
polypropylene, polyethylene, and other thermoplastic resins are
preferred. Among these, POM, nylon 66, nylon 11, polybutylene
terephthalate, polypropylene, and the like are more preferred.
These thermoplastic resins can be used either alone or in
combination.
[0044] The thermoplastic resin or resins can be used in combination
with one or more thermosetting resins. As stated above, the
thermosetting resins that can be used in the present invention
include, but are not limited to, phenolics, diaryl phthalate
resins, unsaturated polyester resins, epoxies, polyimides, triazine
resins system, and the like.
[0045] In a preferred embodiment, the RBC or CRBC should constitute
about 30-70% by weight of the synthetic composition. For example,
the weight ratio of the fine particles of RBC or CRBC to the
synthetic resin should be about 30 to 90:70 to 10. It has been
found that if the synthetic resin exceeds about 70 weight percent,
the difference between the static friction coefficient .mu..sub.S
and the dynamic friction coefficient .mu..sub.D becomes too large.
On the other hand, if it is less than about 10 weight percent,
molding becomes difficult.
[0046] The low noise synthetic resin composition of the present
invention can be molded into any given shape by any of the known
methods. Preferably, the molded compositions are used in the
manufacture of machine elements, such as, for example, screws,
bearings, axial relays, cam mechanisms, cylinders and pistons,
wheels, belts and pulleys, chains and sprockets, valves and tubes,
and the like.
[0047] Preferably, molding is carried out by extrusion molding,
injection molding or by any of the known methods. Preferably, the
temperature of the mold should be relatively low, preferably in the
range between the glass transition point of the synthetic resin and
its fusion point. It is also preferred that the mold be cooled
gradually rather than suddenly, which will normally provide a
molded product having superior surface conditions.
[0048] In a preferred embodiment, the strength of the molded
product can be increased by adding inorganic fibers, such as glass
fiber, rock wool, carbon fibers, and the like; synthetic fibers,
such as polyester, rayon, polyvinyl alcohol, polyamide, polyolefin,
acrylic, and the like; or natural pulp fibers, such as wood pulp,
Manila hemp, and the like.
[0049] The advantages and the important features of the present
invention will become more apparent from Examples 1-9 set forth
below and FIGS. 3-8.
EXAMPLES
[0050] Examples 1-9 include materials made with and without RBC or
CRBC as an additive. The friction characteristics of each of the
examples was then measured, and the examples without RBC or CRBC as
additives were compared to examples with RBC or CRBC as an
additive.
[0051] FIGS. 3-8 each show the dynamic friction coefficient,
.mu..sub.D versus the slide speed, v.sub.s, for Examples 1-9
(materials with and without RBC or CRBC particulate additives).
Measurements were made of the dynamic coefficient of friction,
.mu..sub.D, over a range of sliding speeds, v.sub.s, from 0.001 m/s
to 1.0 m/s for various materials, e.g., in the range of 0.001-0.01
m/s and 0.1-1 m/s. A normal force, n, of 0.49 Newtons (N) was
applied, pressing a SUJ ball with a diameter of 2 millimeters (mm)
into contact with the surface of a specimen.
[0052] A reciprocating friction test apparatus was used to measure
the dynamic friction force for sliding speeds in the range from
0.001 m/s to 0.01 m/s, and a rotary friction test apparatus was
used to measure the dynamic friction force, f.sub.k, at higher
velocities from 0.1 m/s to 1 m/s. In the case of the reciprocating
friction test, the reciprocating arm repeated 1000 strokes and the
stroke distance was 5 mm, which was a distance sufficient to reach
a steady measurement of the dynamic friction force, f.sub.k, which
was used to calculate .mu..sub.D.
[0053] As shown below, the specimens were prepared by injecting
heated materials into a metal mould to produce a circular specimen
with a diameter of 50 mm and a thickness of 3 mm. The injection
temperature varied, depending on the compositions of the materials
used in each of the examples, as noted below. An ester lubricating
oil was applied to surface of the material prior to each test.
[0054] FIGS. 3-8 demonstrate that the materials without RBC or CRBC
particulate additives show stick-slip behavior, and the materials
with RBC or CRBC particulate additives show little or no stick-slip
behavior. Instead, materials with RBC or CRBC particulate additives
show a nearly constant dynamic friction coefficient, .mu..sub.D,
over the full range of slide speeds tested, even at sliding speeds
as low as 0.001 m/s. Thus, the specific examples described below
indicate that materials with RBC or CRBC particulate additives
reduce stick-slip behavior, avoiding the generation of noise.
Example 1
[0055] Preparation of RBC Fine Particles
[0056] De-fatted rice bran in the amount of 75 kilograms and 25
kilograms of phenolic resin (resol) were mixed and kneaded while
being heated at a temperature of 50-60.degree. C. A plastic mixture
of uniform quality, i.e., a homogenous mixture, was obtained.
[0057] The mixture was fired in a rotary kiln for 120 minutes at
900.degree. C. in a nitrogen atmosphere. The resulting carbonized
product was sifted through a 170-mesh sieve. Fine RBC particles
having a mean particle size in the range of 145 to 155 .mu.m were
obtained.
[0058] Preparation of Mixture of RBC Fine Particles and Synthetic
Resin
[0059] RBC fine particles in the amount of 500 grams (having a mean
particle size of 150 .mu.m) and 500 grams of polyacetal resin (POM)
pellets were mixed and kneaded, while being heated at a temperature
of 180-230.degree. C. A plastic mixture of uniform quality was
obtained.
[0060] Molding of Test Pieces
[0061] The above resin composition, heated at a temperature of
190.degree. C., was injected into a metal mold (in the range
between 115.degree. C. and 135.degree. C.) to produce test pieces 3
millimeters thick and 50 millimeters in diameter.
[0062] Measurement of Friction Characteristics
[0063] The results are shown in FIG. 3.
Example 2
[0064] Preparation of Fine RBC Particles
[0065] De-fatted rice bran in the amount of 75 kilograms and 25
kilograms of a liquid phenolic resin (resol) were mixed and kneaded
while being heated at 50-60.degree. C. A plastic mixture having
uniform quality was obtained.
[0066] The mixture was fired at 1,000.degree. C. for 120 minutes in
a rotary kiln in a nitrogen atmosphere. The resulting carbonized
product was sifted through a 170-mesh sieve yielding RBC particles
having a mean particle size in the range of from 145 to 155
.mu.m.
[0067] Preparation of Mixture of Fine RBC Particles and Synthetic
Resin
[0068] RBC particles in the amount of 200 grams (whose mean
particle diameter was 150 .mu.m) and 800 grams of polyacetal resin
(POM) pellets were mixed and kneaded while being heated at
180-200.degree. C. A plastic mixture of uniform quality was
obtained.
[0069] Preparation of Test Pieces
[0070] The above resin composition, heated at a temperature of
190.degree. C., was injected into a metal mold (115 to 135.degree.
C.) to produce test pieces 3 millimeters thick and 50 millimeters
in diameter.
[0071] Measurement of Friction Characteristics
[0072] The results are shown in FIG. 3.
Example 3
[0073] Preparation of Fine RBC Particles
[0074] De-fatted rice bran in the amount of 75 kilograms and 25
kilograms of a liquid phenolic resin (resol) were mixed and kneaded
while being heated at 50-60.degree. C. A plastic mixture of uniform
quality was obtained.
[0075] The mixture was fired at 900.degree. C. for 120 minutes in a
rotary kiln in a nitrogen atmosphere. The resulting carbonized
product was pulverized and sifted through an 800-mesh sieve
yielding RBC particles having a mean particle size of 30 .mu.m.
[0076] Preparation of Mixture of Fine RBC Particles and Synthetic
Resin
[0077] The above RBC particles in the amount of 500 grams and 500
grams of polyamide (nylon 66) pellets were mixed and kneaded while
being heated at 260-280.degree. C. A plastic mixture of uniform
quality was obtained.
[0078] Molding of Test Pieces
[0079] The above resin composition, heated at a temperature of
270.degree. C., was injected into a metal mold (130-150.degree. C.)
to produce test pieces 3 millimeters thick and 50 millimeters in
diameter.
[0080] Measurement of Friction Characteristics
[0081] The results are shown in FIG. 4.
Example 4
[0082] Preparation of a Mixture of Fine RBC Particles and Synthetic
Resin
[0083] RBC particles in the amount of 300 grams obtained in Example
3 having a mean particle size of about 150 .mu.m and 700 grams of
polyamide (nylon 66) pellets were mixed and kneaded while being
heated at 260-280.degree. C.
[0084] Molding of Test Pieces
[0085] The above resin composition, heated at 270.degree. C., was
injected into a metal mold (110-130.degree. C.) to produce test
pieces 3 millimeters thick and 50 millimeters in diameter.
[0086] Measurement of Friction Characteristics
[0087] The results are shown in FIG. 4.
Example 5
[0088] Preparation of Mixture of RBC Fine Particles and Synthetic
Resin
[0089] RBC particles from Example 1 in the amount of 300 grams
having a mean particle size of 150 .mu.m, and 700 grams of
polyamide (nylon 66) pellets were mixed and kneaded while being
heated at 260-280.degree. C. A plastic mixture of uniform quality
was obtained.
[0090] Molding of Test Pieces
[0091] The above resin composition, heated at a temperature of
270.degree. C., was injected into a metal mold (130-140.degree. C.)
to produce a test piece 3 millimeters thick and 50 millimeters in
diameter.
[0092] Measurement of Friction Characteristics
[0093] The results are shown in FIG. 4.
Example 6
[0094] Preparation of Mixture of Fine RBC Particles and Synthetic
Resin
[0095] RBC particles from Example 2 in the amount of 300 grams
having a mean particle size of 150 .mu.m, and 700 grams of
polyamide (nylon 66) pellets were mixed and kneaded while being
heated at 260-280.degree. C. As a result, a plastic mixture of
uniform quality was obtained.
[0096] Next, 100 grams of glass fiber were mixed in. The mixing was
continued for a sufficient time until uniformity was obtained.
[0097] Molding of Test Pieces
[0098] The above resin composition, heated at a temperature of
270.degree. C., was injected into a metal mold (130-140.degree. C.)
to produce test pieces 3 millimeters thick and 50 millimeters in
diameter.
[0099] Measurement of Friction Characteristics
[0100] The results are shown in FIG. 5.
Example 7
[0101] Preparation of Fine CRBC Particles
[0102] De-fatted rice bran in the amount of 75 kilograms and 25
kilograms of liquid phenolic resin (resol) were mixed and kneaded
at 50-60.degree. C. A plastic mixture of uniform quality was
obtained.
[0103] The mixture was fired at 900.degree. C. for 100 minutes in a
rotary kiln in a nitrogen atmosphere. The resulting carbonized
product was crushed with a pulverizer and sifted through a 100-mesh
sieve yielding RBC particles having a mean particle size in the
range of 240 to 260 .mu.m.
[0104] RBC particles in the amount of 75 kilograms and 50 kilograms
of a solid phenolic resin (resol) were mixed and kneaded while
being heated at 50-60.degree. C. A plastic mixture of uniform
quality was obtained.
[0105] Next, the plastic mixture was molded under a pressure of 22
Mpa into a globular shape whose diameter was approximately 1
centimeter. The temperature of the metal mold was 150.degree.
C.
[0106] The molded product was taken out of the metal mold, and the
temperature was elevated at a rate of 2.degree. C. per minute,
until 500.degree. C. was reached. The temperature was held for 60
minutes at 500.degree. C., and then firing was carried out at
900.degree. C. for approximately 120 minutes.
[0107] Next, the temperature was lowered at a cooling rate of 2 to
3.degree. C. per minute until 500.degree. C. was reached. Below
500.degree. C., it was left to cool naturally.
[0108] The resulting CRBC product was crushed with a pulverizer
and, by using a 170-mesh sieve, CRBC particles having a mean
particle size of from 145 to 155 .mu.m were obtained.
[0109] Preparation of Mixture of Fine CRBC Particles and Synthetic
Resin
[0110] CRBC particles in the amount of 600 grams and 400 grams of
polyamide (nylon 11) pellets were mixed and kneaded while being
heated at 190-200.degree. C. A plastic mixture of uniform quality
was obtained.
[0111] Molding of Test Pieces
[0112] The above resin composition, heated at a temperature of
200.degree. C., was injected into a metal mold (90-110.degree. C.)
to produce test pieces three millimeters thick and 50 millimeters
in diameter.
[0113] Measurement of the Friction Characteristics
[0114] The results are shown in FIG. 6.
Example 8
[0115] Preparation of Fine CRBC Particles
[0116] De-fatted rice bran in the amount of 75 kilograms and 25
kilograms of a liquid phenolic resin (resol) were mixed and kneaded
while being heated at 50-60.degree. C. A plastic mixture of uniform
quality was obtained.
[0117] The mixture was fired at 950.degree. C. in a rotary kiln for
120 minutes in a nitrogen atmosphere. The resulting carbonized
product was pulverized and then sifted through a 100-mesh sieve to
yield RBC particles having a mean particle size of from about 240
to 260 .mu.m.
[0118] RBC particles in the amount of 75 kilograms and 35 kilograms
of a solid phenolic resin (resol) were mixed and kneaded while
being heated at 50-60.degree. C. A plastic mixture of uniform
quality was obtained.
[0119] Next, the plastic product was molded under a pressure of 22
Mpa into a globular shape whose diameter was approximately 1
centimeter. The temperature of the metal mold was 150.degree.
C.
[0120] The molded product was taken out of the metal mold. The
temperature was then raised in a nitrogen atmosphere at the rate of
3.degree. C. per minute until 500.degree. C. was achieved. It was
held at 500.degree. C. for 30 minutes; and then fired for
approximately 120 minutes at 1000.degree. C.
[0121] Next, the temperature was lowered at a cooling rate of 2 to
3.degree. C. per minute until 500.degree. C. was reached, then left
to cool naturally.
[0122] The resulting CRBC product was pulverized and subjected to a
170-mesh sieve yielding CRBC particles having a mean particle size
of 145 to 155 .mu.m.
[0123] Preparation of Mixture of Fine CRBC Particles and Synthetic
Resin
[0124] CRBC particles in the amount of 600 grams, having a mean
particle size of 150 .mu.m, and 400 grams of polybutylene
terephthalate powder were mixed and kneaded while being heated at
240-260.degree. C. A plastic mixture of uniform quality was
obtained.
[0125] Molding of Test Pieces
[0126] The above resin composition, heated at a temperature of
260.degree. C., was injected into a metal mold (80-100.degree. C.)
to produce test pieces 3 millimeters thick and 50 millimeters in
diameter.
[0127] Measurement of Friction Characteristics
[0128] The results are shown in FIG. 7.
Example 9
[0129] Preparation of Mixture of Fine CRBC Particles and Synthetic
Resin
[0130] CRBC particles in the amount of 700 grams from Example 8
(having a mean particle size of 150 .mu.m) and 300 grams of
polypropylene particles were mixed and kneaded while being heated
at 190-210.degree. C. A plastic mixture of uniform quality was
obtained.
[0131] Molding of Test Pieces
[0132] The above resin composition, heated at a temperature of
220.degree. C., was injected into a metal mold (80-90.degree. C.)
to produce test pieces 5 millimeters thick and 50 millimeters in
diameter.
[0133] Measurement of Friction Characteristics
[0134] The results are shown in FIG. 8.
[0135] The results from FIGS. 3-8 clearly show that the synthetic
resin composition that contains fine particles of RBC or CRBC of
the present invention is a material in which the difference between
the static friction coefficient .mu..sub.S and dynamic friction
coefficient .mu..sub.D is small. As a result, the stick-slip
phenomenon is significantly reduced, thereby allowing the
composition of the present invention to have a wide range of uses
for various kinds of machinery elements.
[0136] Although the present invention has been described in
relation to particular embodiments thereof, many other variations
and modifications and other uses will become apparent to those
skilled in the art. The present invention therefore is not limited
by the specific disclosure herein.
* * * * *