U.S. patent application number 11/202096 was filed with the patent office on 2005-12-01 for method of vulcanizing an object formed of unvulcanized rubber and rubber product.
This patent application is currently assigned to The Yokohama Rubber Co., Ltd.. Invention is credited to Ohishi, Hideyuki, Tamada, Yoshinori, Yanadori, Kazuhito.
Application Number | 20050263245 11/202096 |
Document ID | / |
Family ID | 27481801 |
Filed Date | 2005-12-01 |
United States Patent
Application |
20050263245 |
Kind Code |
A1 |
Yanadori, Kazuhito ; et
al. |
December 1, 2005 |
Method of vulcanizing an object formed of unvulcanized rubber and
rubber product
Abstract
A method of vulcanizing an object formed of unvulcanized rubber,
in which the unvulcanized-rubber formed object is vulcanized by
pressing and heating by mold means, comprises disposing a fiber
sheet member on a surface of the unvulcanized-rubber formed object
and vulcanizing the unvulcanized-rubber formed object by the mold
means.
Inventors: |
Yanadori, Kazuhito;
(Hiratsuka-shi, JP) ; Ohishi, Hideyuki;
(Hiratsuka-shi, JP) ; Tamada, Yoshinori;
(Hiratsuka-shi, JP) |
Correspondence
Address: |
RADER FISHMAN & GRAUER PLLC
LION BUILDING
1233 20TH STREET N.W., SUITE 501
WASHINGTON
DC
20036
US
|
Assignee: |
The Yokohama Rubber Co.,
Ltd.
|
Family ID: |
27481801 |
Appl. No.: |
11/202096 |
Filed: |
August 12, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11202096 |
Aug 12, 2005 |
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10181685 |
Jul 19, 2002 |
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10181685 |
Jul 19, 2002 |
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PCT/JP01/10008 |
Nov 16, 2001 |
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Current U.S.
Class: |
156/307.1 ;
198/846 |
Current CPC
Class: |
B29C 35/02 20130101;
B29L 2031/7092 20130101; Y10T 156/109 20150115; B29K 2021/00
20130101; B29D 29/06 20130101 |
Class at
Publication: |
156/307.1 ;
198/846 |
International
Class: |
B32B 031/26 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 20, 2000 |
JP |
2000-352423 |
Aug 8, 2001 |
JP |
2001-241109 |
Oct 10, 2001 |
JP |
2001-312862 |
Oct 16, 2001 |
JP |
2001-318165 |
Claims
1. A method of vulcanizing an object formed of unvulcanized rubber
in which the unvulcanized-rubber formed object is vulcanized by
pressing and heating by mold means, comprising; disposing a fiber
sheet member on a surface of said unvulcanized-rubber formed
object; and vulcanizing the unvulcanized-rubber formed object by
said mold means.
2. A method of vulcanizing an object formed of unvulcanized rubber
according to claim 1, wherein said fiber sheet member is selected
from textile fabric or nonwoven fabric.
3. A method of vulcanizing an object formed of unvulcanized rubber
according to claim 1 or 2, wherein said fiber sheet member is
formed of fiber material having a melting point higher than
vulcanizing temperature.
4. A method of vulcanizing an object formed of unvulcanized rubber
according to claim 3, wherein the fiber material of said fiber
sheet member has a melting point equal to 180.degree. C. or
higher.
5. A method of vulcanizing an object formed of unvulcanized rubber
according to claim 2, wherein said fiber sheet member comprises a
textile fabric, and the mass per unit area of the fiber sheet
member is 5 to 30 g/m.sup.2.
6. A method of vulcanizing an object formed of unvulcanized rubber
according to claim 5, wherein the thickness of said fiber sheet
member is 0.05 to 0.40 mm.
7. A method of vulcanizing an object formed of unvulcanized rubber
according to claim 2, wherein said fiber sheet member comprises a
nonwoven fabric, and the mass per unit area of the fiber sheet
member is 10 to 25 g/m.sup.2.
8. A method of vulcanizing an object formed of unvulcanized rubber
according to claim 7, wherein the thickness of said fiber sheet
member is 0.05 to 0.20 mm.
9. A method of vulcanizing an object formed of unvulcanized rubber
according to any one of claims 1, 2 and 5 to 8, wherein said fiber
sheet member is disposed on surfaces of the unvulcanized-rubber
formed objects end portions of which come into contact with each
other.
10. A method of vulcanizing an object formed of unvulcanized rubber
according to any one of claims 1, 2 and 5 to 8, wherein said fiber
sheet member is pressed on the surface of said unvulcanized-rubber
formed object.
11. A method of vulcanizing an object formed of unvulcanized rubber
according to any one of claims 1, 2 and 5 to 8, wherein said mold
means is a vulcanizing belt press having upper and lower heat
plates for pressing and heating.
12. A rubber product comprising a vulcanized-rubber formed object
and a fiber sheet member embeded in a surface portion thereof.
Description
TECHNICAL FIELD
[0001] This invention relates to a method of vulcanizing an object
formed of unvulcanized rubber and a rubber product produced thereby
and, more particularly, to a method of vulcanizing an object formed
of unvulcanized rubber and a rubber product produced thereby in
which the appearance of the rubber product is improved.
BACKGROUND ART
[0002] For example, there is an unvulcanized rubber sheet for a
conveyor belt as an unvulcanized-rubber formed object. This
unvulcanized rubber sheet for a conveyor belt is generally
vulcanized and molded using a vulcanizing belt press. During the
process of vulcanizing, due to entrapped air, and due to gas, water
and the like generated from the unvulcanized rubber material,
clearances are produced between the heat plate of the vulcanizing
belt press and the surface of the unvulcanized rubber sheet pressed
by the heat plate, thereby forming depressions on the obtained
conveyor belt surfaces. Therefore, the conveyor belt surface cannot
present a substantially smooth and glossy surface and there is a
problem of having a bad appearance. Particularly in these years, a
good appearance is desired by users in addition to an excellent
property.
[0003] To solve the above problem, there is conventionally employed
a method of coating powder of, for example, zinc stearate, talc,
mica or the like on the surface of the unvulcanized rubber sheet.
By coating this powder, the entrapped air, and the gas and water
(steam) generated from the rubber material (inside) between the
heat plate and the unvulcanized rubber sheet at the time of
vulcanizing can be exhausted to the outside via the clearance
formed between the powder and the heat plate. Accordingly, the
generation of depressions is restricted and the conveyor belt which
improves appearance can be obtained.
[0004] However, in the method of coating powder as described above,
due to the insufficient clearance between the unvulcanized rubber
sheet and the heat plate, there is a problem that the air and gas
cannot be exhausted effectively. Since the powder scatters when
coated, there is also a problem of harmful influence on the working
environment.
[0005] Further as the other method, in Japanese Patent No. 2588209,
there is proposed a method for vulcanizing an unvulcanized rubber
sheet that has a sheet-like sponge member adhered to the surface
thereof, the sheet-like sponge member having a continuous
clearance. During vulcanization by a vulcanizing belt press, the
rubber being gradually softened enters into the clearance of the
sponge member and the rubber pushes out the residue air and the
like through the continuous clearance to the outside. Therefore,
the generation of the residue air is prevented and depressions is
not produced on the surface of the obtained conveyor belt
[0006] However, in the method using the sponge member, the sponge
member is so excellent in expansion that, when adhered to the
unvulcanized rubber sheet surface by pressing, the sponge member
extends to the longitudinal direction and reduces with respect to
the width direction. Therefore, when the sponge member is adhered
to the unvulcanized rubber sheet surface, it is likely to generate
a part that is lack of the sponge member in one or both end
portions of the width direction of the unvulcanized rubber sheet
surface. Accordingly, it is difficult to adhere the sponge member
through the whole surface of the unvulcanized rubber sheet, and a
problem of deteriorating press-processing efficiency is caused.
Further, since the obtained conveyor belt has a structure such that
the sponge member having a low strength is disposed on the surface,
the abrasion resistance of the surface is deteriorated.
DISCLOSURE OF THE INVENTION
[0007] It is an object of the invention to provide a method of
vulcanizing an object formed of unvulcanized rubber and a rubber
product obtained thereby, capable of improving the appearance of
the obtained rubber product while not harmfully influencing on the
work environment, and not deteriorating the press-processing
efficiency or product property.
[0008] To achieve the above object, a method of vulcanizing an
object formed of unvulcanized rubber according to the present
invention, in which the unvulcanized-rubber formed object is
vulcanized by pressing and heating by mold means, comprises
disposing a fiber sheet member on a surface of the
unvulcanized-rubber formed object and vulcanizing the
unvulcanized-rubber formed object by the mold means.
[0009] A rubber product according to the present invention
comprises a vulcanized-rubber formed object and a fiber sheet
member embeded in a surface portion thereof.
[0010] In accordance with the present invention, since the fiber
sheet member is disposed on a surface of the unvulcanized-rubber
formed object to be vulcanized, the residue air, and gas and water
generated from the unvulcanized rubber material can be effectively
pushed out to the outside of the mold means by the rubber gradually
softening and entering into the clearance of the fiber sheet
member. Therefore, the surface of the obtained rubber product can
be prevented from generating depressions. Thus, the surface of the
obtained rubber product can present a substantially smooth and
glossy surface and the rubber product can have a good
appearance.
[0011] A good working environment can always be maintained, because
no powder harmfully affecting on the working environment is used.
Since the fiber sheet member is not extended or contracted so much
as the sponge member and has a greater strength than that, the
press-processing efficiency is prevented from deterioration if the
fiber sheet member is pressed onto the unvulcanized-rubber formed
object, and the abrasion resistance of the rubber product surface
is not lowered.
BRIEF DESCRIPTION OF DRAWINGS
[0012] FIG. 1 is an explanatory view showing one example of a
method for vulcanizing an unvulcanized-rubber formed object
according to the invention.
[0013] FIG. 2 is an enlarged cross-sectional view showing a main
part of a rubber product obtained by the method in FIG. 1.
[0014] FIG. 3 is an explanatory view showing another example of a
method for vulcanizing an unvulcanized-rubber formed object
according to the invention.
[0015] FIG. 4 is an enlarged cross-sectional view showing a main
part of another example of the unvulcanized-rubber formed object
used in a method for vulcanizing an unvulcanized-rubber formed
object according to the invention.
[0016] FIG. 5 is an enlarged cross-sectional view showing a main
part of further another example of an unvulcanized-rubber formed
object used in a method for vulcanizing an unvulcanized-rubber
formed object according to the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0017] The embodiments in accordance with the present invention
will be described below with reference to the drawings, using an
unvulcanized rubber sheet for a belt conveyor as an
unvulcanized-rubber formed object.
[0018] As shown in FIG. 1, the numeral 1 shows an unvulcanized
rubber sheet for a conveyor belt in a long belt-like shape, the
numeral 3 long belt type fiber sheet members and the numeral 5 a
mold means for molding the unvulcanized rubber sheet 1.
[0019] The unvulcanized rubber sheet 1 is wound via an
adhesion-preventing liner (not shown) around an unwinding roll 7
which is disposed at the upper flow side of the mold means 5. The
fiber sheet members 3 are wound around upper and lower rolls 9A,
9B, respectively, and stocked there, which are placed between the
unwind roll 7 and the mold means 5.
[0020] Provided between the rolls 9A, 9B and the mold means 5 are
press rollers 11A, 11B for pressing the fiber sheet members 3
unwound from the rolls 9A, 9B onto the upper and lower surfaces 1a,
1b of the unvulcanized rubber sheet 1. At the lower flow side of
the mold means 5, there is disposed a winding roll 13 for winding a
vulcanized rubber sheet 1Y that has been vulcanized by the mold
means 5. The mold means 5 is a vulcanizing belt press having upper
and lower heat plates 5A, 5B capable of moving up and down to press
and heat the unvulcanized rubber sheet 1.
[0021] In the vulcanization method of the present invention, first,
the unvulcanized rubber sheet 1 is unwound from the unwind roll 7
as shown by an arrow a, and is supplied to the direction shown by
an arrow b while removing the adhesion-preventing liner (not
shown). The fiber sheet members 3 are unwound from the rolls 9A, 9B
toward the direction shown by arrows c, and pressed and adhered to
the upper and lower surfaces 1a, 1b of the unvulcanized rubber
sheet 1 by the press rollers 11A, 11B consecutively.
[0022] The unvulcanized rubber sheet 1X provided with the fiber
sheet members 3 on the both surfaces thereof is then transported
between the upper and lower heat plates 5A, 5B. The upper and lower
heat plates 5A, 5B, respectively, at the upper and lower waiting
positions are moved toward the unvulcanized rubber sheet 1X to
press and heat it for vulcanization. At the time of vulcanizing,
air entrapped, and gas, water, etc., produced from the unvulcanized
rubber material remain between the heat plates 5A, 5B and the upper
and lower surfaces 1a, 1b of the unvulcanized rubber sheet 1.
[0023] The unvulcanized rubber sheet 1X pressed and heated between
the heat plates 5A, 5B is softened from the central portion toward
the peripheral portion. Therefore the softened rubber enters from
the central portion side of each of the fiber sheet members 3 into
the clearance of the fiber sheet member 3, gradually pushes the
air, the gas, and the water toward the outside thereof and finally
excludes them to the outside of heat plates 5A, 5B.
[0024] The heat plates 5A, 5B separate from each other when the
vulcanization is terminated. As a result, as shown in FIG. 2, a
conveyor belt (rubber product) can be obtained having the fiber
sheet members 3 embeded in the surface portions of the vulcanized
rubber sheet (vulcanized-rubber formed object) 1Y. As shown by an
arrow d, the vulcanized rubber sheet 1Y is transported towards the
unwind roll 7 and is wound around the unwind roll 7 as shown by an
arrow e. In FIG. 2, the numeral 2 shows reinforce layers embeded in
the vulcanized rubber sheet 1Y.
[0025] In accordance with the present invention, since the fiber
sheet members 3 are disposed on the surfaces 1a, 1b of the
unvulcanized rubber sheet 1 to be vulcanized, the residue air, gas,
and water can be effectively excluded from the clearance of the
fiber sheet members 3 to the outside thereof. Therefore, no
depression appears on the surfaces of the obtained conveyor belt
unlike the prior art. Accordingly, the surfaces of the conveyor
belt are substantially smooth and glossy, and the appearance of the
conveyor belt can be improved.
[0026] The deterioration of working environment can be prevented
because no powder which deteriorates the working environment is
used. In addition, since the fiber sheet members 3 do not extend
much unlike the sponge members, the press-processing efficiency can
not be lowered even if the fiber sheet members 3 are pressed on the
unvulcanized rubber sheet 1. The fiber sheet members 3 are greater
in strength than the sponge members, so the resistance of the
surfaces of the obtained conveyor belt to abrasion is not
deteriorated.
[0027] FIG. 3 shows another example of a method for vulcanizing an
unvulcanized-rubber formed object according to the present
invention. In this embodiment, in place of the unvulcanized rubber
sheet wound around the unwind roll 7, an unvulcanized rubber sheet
1 pressed out by an extruder 15 is used. This unvulcanized rubber
sheet 1 has no reinforce layers 2 described above. In this way the
unvulcanized rubber sheet 1 extruded from the extruder 15 may be
directly used without winding it around the unwinding roll 7. The
same components as those in FIG. 1 have the same numerals and the
description thereof will be omitted.
[0028] FIG. 4 shows another example of the unvulcanized rubber
sheet used for the vulcanizing method of the present invention.
This embodiment illustrates a conveyer belt formed into one unit by
vulcanization from two unvulcanized rubber sheets 1, end portions
1e of which are overlapped in contact with each other. Fiber sheet
members 3 are respectively adhered onto the upper and lower
surfaces 1a, 1b of the unvulcanized rubber sheets 1 the end
portions 1e of which are brought into contact with each other as
describe above, and the rubber sheets are then disposed between the
upper and lower heat plates 5A, 5B of the vulcanizing belt press
and vulcanized. The obtained conveyor belt having the end portions
1e which have been integrally connected with each other can exhibit
the same effects described above.
[0029] FIG. 5 illustrates further another example of the
unvulcanized rubber sheet used for the vulcanizing method of the
present invention. In this embodiment, unvulcanized rubber sheets
1L, 1M, 1N, 1P, 1Q are unitarily joined by vulcanization to obtain
a conveyer belt.
[0030] The end portions 1e of the first unvulcanized rubber sheet
1L and second unvulcanized rubber sheet 1M on the lower side butt
against each other. The third unvulcanized rubber sheet 1N embeded
with a reinforce layer 2 is laminated on the unvulcanized rubber
sheets 1L, 1M. The fourth and fifth unvulcanized rubber sheets 1P,
1Q are laminated on the third unvulcanized rubber sheet 1N. As in
the first and second unvulcanized rubber sheets 1L, 1M, end
portions 1e of the fourth and the fifth unvulcanized rubber sheets
1P, 1Q, butt against each other.
[0031] Fiber sheet members 3 are respectively adhered onto the
upper and lower surfaces 1Ta, 1Tb of the unvulcanized rubber sheet
laminate 1T of the above structure, and the laminate 1T is then
placed between the upper and lower heat plates 5A, 5B and
vulcanized. The obtained conveyor belt comprising the rubber sheets
1L, 1M, 1N, 1P, 1Q which have joined into one unit, can exhibit the
same effects described above.
[0032] In the present invention, the fiber sheet members 3 may be
used having any of such structures capable of exhausting the
residue air or the like to the outside through the clearance during
vulcanization. For example, textile fabrics or knit fabrics in
sheet can be preferably used. Nonwoven fabrics may also be
used.
[0033] For fiber materials of the fiber sheet members 3, any of
fiber materials having a higher melting point than the vulcanizing
temperature may be used. For instance, nylon fiber, polyester
fiber, etc., having a melting point of 180.degree. C. or more can
be preferably employed.
[0034] When textile fabrics or knit fabrics are used for the fiber
sheet members 3, it is preferable that the mass per unit area
thereof may be 5 to 30 g/m.sup.2. If the mass per unit area is less
than 5 g/m.sup.2, the generation of crinkling can easily happen
when the fiber sheet members 3 are adhered onto the unvulcanized
rubber sheet 1 by pressing. And since it is difficult to
effectively exclude the air, etc., depressions can easily be
produced. If the mass per unit area is more than 30 g/m.sup.2, the
consumption volume of the fiber sheet members 3 is be too exceeded.
Since the difference between the color of the fiber sheet members 3
embeded in the surface portions and the original color (black in
general) of the vulcanized rubber becomes apparent, the appearance
is deteriorated. Moreover, as the adhesion between the fiber sheet
members 3 and the vulcanized rubber is lowered, the abrasion
resistance of the surfaces of the obtained conveyor belt is
lowered.
[0035] The thickness of the fiber sheet members 3 using textile
fabrics or knit fabrics may be preferably 0.05 to 0.40 mm. If the
thickness is out of the above range, the same problems as described
in case of the mass per unit area are caused.
[0036] In case of using nonwoven fabrics for the fiber sheet
members 3, it is preferable that the mass per unit area is 10 to 25
g/m.sup.2. The thickness thereof may preferably be 0.05 to 0.20 mm.
If the mass per unit area and the thickness are out of the above
ranges, the same problems as described above are caused.
[0037] In case of using nonwoven fabrics for conveyor belts, at
least in the direction of the compressive stress acting upon the
conveyer belt, it is preferable that the extension degree at the
time of cutting is set to be 25% or more and the extension degree
under {fraction (1/10)} of load of the cutting strength is set to
be 10% or more. These may be set in the same manner for the case of
other rubber products.
[0038] If the extension degree at the time of cutting is less than
25%, or the extension degree under {fraction (1/10)} of load of the
cutting strength is less than 10%, the nonwoven fabric, when the
compressive stress acts upon the belt in services, is buckled, and
crinkling occurs on the conveyor belt surfaces. Therefore, the belt
appearance is deteriorated and the surface abrasion resistance is
lowered. It is preferable that the upper limit value of the
extension degree in cutting is 50% and the upper limit value of the
extension degree under {fraction (1/10)} of load of the cutting
strength is set to be 20%. If the extension degrees exceed these
upper limit values, the fiber sheet members extend greatly, thereby
deteriorating the press-processing efficiency as in the sponge
member.
[0039] In these embodiments, the unvulcanized rubber sheets for a
conveyor belt are described as examples of the unvulcanized-rubber
formed objects. However, the present invention is not limited
thereto and will be adequately used for any of unvulcanized-rubber
formed objects, which have the same problems as described in the
prior art.
EXAMPLE 1
[0040] Conveyer belts having a structure shown in FIG. 2 were
prepared by vulcanizing unvulcanized rubber sheets for a conveyor
belt by the vulcanizing methods 1 to 3 of the present invention,
the unvulcanized rubber sheets having fiber sheet members shown in
Table 1. Each fiber sheet member was made of Nylon 6, and its mass
per unit area was 10 g/m.sup.2 and the thickness thereof was 0.2
mm.
[0041] Conveyer belts having a structure with no fiber sheet member
in FIG. 2 were also prepared by vulcanizing unvulcanized rubber
sheets for a conveyor belt by the conventional vulcanizing method
using powder of zinc stearate (conventional method 1) and by the
conventional vulcanizing method using talc powder (conventional
method 2). The powder was applied for 10 g per 1 m.sup.2 in each
vulcanizing methods.
[0042] A conveyer belt having sponge members made of polyurethane
(a thickness of 1 mm) in place of the fiber sheet members in the
conveyer belt with a structure of FIG. 2 was also prepared by
vulcanizing an unvulcanized rubber sheet by the conventional
vulcanizing method (the conventional method 3) using the sponge
members.
[0043] In each vulcanizing method, a vulcanizing belt press was
used, the vulcanization temperature being 150.degree. C., the
vulcanization time period being 30 minutes. Rubber (NR/SBR system
rubber) mixed with natural rubber and styrene-butadiene rubber was
used for each of the unvulcanized rubber sheets for a conveyor belt
in the vulcanizing methods, and the width of the rubber sheets was
1 m, the thickness 10 mm and the length 20m.
[0044] Evaluation tests for the generation rate of depressions,
surface color condition, working environment, press-processing
efficiency of the fiber sheet members and the sponge members, and
surface abrasion resistance were conducted under the following
measuring conditions to the conveyer belts obtained by the
vulcanizing methods. The results were shown in Table 1.
[0045] Generation Rate of Depressions
[0046] The number of depressions generated on the surfaces of the
conveyor belt which is obtained by each method is counted and the
obtained number is converted into the generation rate per 10
m.sup.2.
[0047] Surface Color Condition
[0048] The test is conducted in accordance with JIS Z8723, "Visual
Comparative Evaluation of Surface Color". The results are evaluated
in three ranks by .largecircle., .DELTA., X. .largecircle. means no
problem and a good condition (if any, however little), .DELTA.
means that some problem exists (depressions are clearly confirmed),
and X means that a great problem exists (the generation of
depressions are seen in a wide range) and considerable
deterioration is caused.
[0049] Working Environment
[0050] After producing each conveyor belt by each vulcanizing
method, the polluted state in the whole processes including the
equipment is observed. The results are evaluated in three ranks by
.largecircle., .DELTA., X. .largecircle. means no problem and a
good state, .DELTA. means that some problem exists, and X means
that a great problem exists and considerable deterioration is
caused.
[0051] Press-Processing Efficiency of Fiber Sheet Member and Sponge
Member
[0052] At the time of producing the conveyor belt, after pressing
the fiber sheet members and the sponge members onto the surfaces of
the unvulcanized rubber sheets by press rollers, the adhesion state
of each fiber sheet member or sponge member on the surface of the
sheet obtained is visually observed. The results are evaluated in
three ranks by .largecircle., .DELTA., X. .largecircle. means no
problem and a good state, .DELTA. means that some problem exists,
and X means that a great problem exists (in a wide range of
unvulcanized rubber sheet surface, portions lack of the fiber sheet
member or the sponge member are generated, or crinkling is
observed) and considerable deterioration is caused.
[0053] Surface Abrasion Resistance
[0054] The conveyor belt obtained by each method is cut into a
rectangular test piece having a width of 25 mm and a length of 40
cm. The test piece is bent one million times under the condition of
a pulley diameter of 50 mm, load of 250 N/overall width, according
to Press and Bending Fatigue Strength Evaluation (A Method) which
is described in JIS L1017. The surface of each test piece is then
visually observed. The results are evaluated in three ranks by
.largecircle., .DELTA., X. .largecircle. means no problem and a
good state such that only the outer rubber surface of the test
piece is abraded and little generation of fuzz, rough surface, and
detachment of the fiber sheet member or of the sponge member can be
observed, .DELTA. means some problem such that fuzz, rough surface
and/or detachment of the fiber sheet member or of the sponge member
can be slightly observed, and X means a great problem such that
fuzz, rough surface and/or detachment of the fiber sheet member or
of the sponge member can be apparently observed and considerable
deterioration is caused.
1 TABLE 1 Method 2 Method 3 Method 1 of of the of the the Present
Present Present Conventional Conventional Conventional invention
invention invention Method 1 Method 2 Method 3 Fiber Sheet Knit
Textile Nonwoven -- -- -- Member fabric fabric fabric Generation
Rate 0 0 0 1.3 1.1 0 of Depressions (number/10 m.sup.2) Surface
Color .largecircle. .largecircle. .largecircle. .largecircle.
.DELTA. .largecircle. Condition Working .largecircle. .largecircle.
.largecircle. .DELTA. .DELTA. .largecircle. Environment Press-
.largecircle. .largecircle. .largecircle. -- -- X Processing
Efficiency Surface .largecircle. .largecircle. .largecircle.
.largecircle. .largecircle. .DELTA. Abrasion Resistance
[0055] As shown in Table 1, the vulcanizing methods of the present
invention can obtain conveyer belts (rubber products) having a good
appearance, without deteriorating the working environment, the
press-processing efficiency of the fiber sheet member and the
surface abrasion resistance.
EXAMPLE 2
[0056] Fiber sheet members were prepared each having the mass per
unit shown in Table 2, the fiber sheet members being made of the
same knit fabric as used in the example 1. Unvulcanized rubber
sheets with these fiber sheet members were vulcanized by
vulcanizing methods using the fiber sheet members (Methods A to E),
and conveyor belts having a composition as shown in FIG. 2 were
obtained. Other conditions were the same as in the example 1.
[0057] Evaluation tests for the generation rate of depressions,
surface color condition, working environment, press-processing
efficiency of the fiber sheet members and the sponge members, and
surface abrasion resistance were conducted under the same measuring
conditions as shown in the example 1 to the conveyer belts obtained
by the vulcanizing methods. The results were shown in Table 2.
2 TABLE 2 Vulcanizing Vulcanizing Vulcanizing Vulcanizing
Vulcanizing Method A Method B Method C Method D Method E Unit Mass
4 5 10 30 35 (g/m.sup.2) Generation Rate 0.2 0 0 0 0 of Depressions
(number/10 cm.sup.2) Surface Color .largecircle. .largecircle.
.largecircle. .largecircle. .DELTA..about.X Condition Working
.largecircle. .largecircle. .largecircle. .largecircle.
.largecircle. Environment Press-Processing X .largecircle.
.largecircle. .largecircle. .largecircle. Efficiency (crinkling)
Surface Abrasion .largecircle. .largecircle. .largecircle.
.largecircle. .DELTA..about.X Resistance
[0058] As shown in Table 2, it is understood that the mass per unit
area of the fiber sheet members composed of knit-fabric is
preferably 5 to 30 g/m.sup.2.
EXAMPLE 3
[0059] Fiber sheet members were prepared each having the mass per
unit shown in Table 3, the fiber sheet members being made of the
same nonwoven fabric as used in the example 1. Each nonwoven fabric
was arranged such that the extension degree at the time of cutting
was 35%, and the extension degree under {fraction (1/10)} of load
of the cutting strength was 14%. Unvulcanized rubber sheets with
these fiber sheet members were vulcanized by vulcanizing methods
using the fiber sheet members (Methods F to J), and conveyor belts
having a composition as shown in FIG. 2 were obtained. Other
conditions were the same as in the example 1.
[0060] Evaluation tests for the generation rate of depressions,
surface color condition, working environment, press-processing
efficiency of the fiber sheet members and the sponge members, and
surface abrasion resistance were conducted under the same measuring
conditions as shown in the example 1 to the conveyer belts obtained
by the vulcanizing methods. The results were shown in Table 3.
3 TABLE 3 Vulcanizing Vulcanizing Vulcanizing Vulcanizing
Vulcanizing Method F Method G Method H Method I Method J Unit Mass
7 10 15 25 30 (g/m.sup.2) Generation Rate 0.2 0 0 0 0 of
Depressions (number/10 cm.sup.2) Surface Color .largecircle.
.largecircle. .largecircle. .largecircle. X Condition Working
.largecircle. .largecircle. .largecircle. .largecircle.
.largecircle. Environment Press-Processing X .largecircle.
.largecircle. .largecircle. .largecircle. Efficiency (crinkling)
Surface Abrasion .largecircle. .largecircle. .largecircle.
.largecircle. .DELTA. Resistance
[0061] As shown in Table 3, it is understood that the mass per unit
area of the fiber sheet members made of nonwoven fabric is
preferably 10 to 25 g/m.sup.2.
[0062] As described above, according to the method of the present
invention for vulcanizing an object formed of unvulcanized rubber,
since the fiber sheet member is disposed on the surface of the
unvulcanized-formed object to be vulcanized, the residue air and
the like can be excluded from the clearance of the fiber sheet
member to the outside during vulcanization. Therefore, depressions
produced on the surface of the obtained rubber produce can be
prevented. Accordingly, the surface of the rubber product obtained
can be substantially smooth and glossy and it has a good
appearance.
[0063] Since powder harmfully affecting on the working environment
is not used, a good working environment can be maintained. In
addition, the fiber sheet member has a higher strength than the
sponge member, and is not easily extended or contracted, so the
processing efficiency at the time of pressing and surface abrasion
resistance can not be lowered.
POSSIBILITY OF INDUSTRIAL USE
[0064] The vulcanizing method of the present invention, which has
excellent effects described above, is very useful to vulcanize
unvulcanied-rubber formed objects in the vulcanizing process when
rubber products such as conveyor belts are produced.
* * * * *