Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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WIPER BLADE
BACKGROUND OF THE INVENTION
1. Field of the Invention:
This invention relates to a wiper blade for wiping the
windshield of a vehicle such as automobile, a streetcar,
or an aircraft.
2. Description of the Prior Art:
The wiser blade used for vehicles
is intended to wipe water drops, snow, etc. away the
windshield surface by sliding on the windshield surface.
It is, therefore, required to give even wiping to the windshield
by being pressed uniformly against the windshield and to
operate smoothly an-d avoid emitting objectionable noise by
offering low frictional resistance.
t has been customary, therefore, to form the wiper blade
with natural rubber, synthetic rubber such as chloroprene rubber,
resin such as polye~len thereby to confer us
thermoplastic elastomers such as urethane type e].astomer, ox synthetic /
the wiper blade the elasticity high enough for the wiper blade
j to slide evenly on the shield surface and, at the same time,
¦ subject the surface of the wiper blade to a treatment of
¦ chlorination or bromination thereby to cause bonding of
chlorine atoms or bromide atoms to the carbon atoms in the
main chain of the rubber or elastomers and induce degradation
of frictional resistance.
The treatment of chlorination or bromination, however,
is incapable of amply lowering the frictional resistance.
Particularly, the Cal bond or Cur bond is chemically instable
,
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and is readily unbounded by heat, water, ultraviolet light,
ozone, oxygen, or chemicals to remove Of or Bra The
conventional wiper blade, therefore, is deficient in resistance
to the conditions of nature and looses the performance as
a wiper blade within a short time.
When the treatment of chlorination, for example, is
carried out to a high degree for the purpose of lowering
the friction resistance and enhancing the durability,
adversely, cracks are produced easily on the surface thereof,
the permanent set resistance is reduced and the striped trace
remains on the surface thereof after wiping, whereby the
wiping properties are lowered.
It is known that the ethylene-propylene copolymer
(hereinafter refried to as EM) and the ethylene-propylene-
dine copolymer (hereinafter referred to as EPDM) obtained
by adding a small amount of a dine compound to EM for
enhancing its valcanizability have a remarkable quality in
resistance to aging, ozone, chemicals, water and
permanent set. The above-mentioned problems, therefore,
can be solved, if EM or EPDM may be used as a material for
the wiper blade.
Since EM and EPDM are saturated organic high molecular
compounds possessing no double bond in the main chains thereof,
however, they form neither Cal bond nor Cur bond even if
they are subjected to the treatment of chlorination or
bromination.
~:3;~0~C~
The present invention is accomplished by studying the
fact that fluorine is extremely active and substitutes for
the hydrogen atom of the C-F bond to form a C-F bond.
SUMMARY OF THE INVENTION
According to this invention, it is provided that a wiper
blade produced by molding a wiper blade matrix of ethylene-
propylene copolymer (EM) or ethylene-propylene-diene copolymer
(EPDM) and fluoridating the wiper blade matrix thereby causing
fluorine atoms to be bonded to the carbon atoms of the
aforementioned copolymer in the surface layer of the wiper
blade matrix.
- An object of this invention, therefore, is to provide
a wiper blade possessing a low friction coefficient and is
excellent in resistance to aging, ozone, chemicals, abrasion,
and permanent set.
The other and further objects and characteristic features
of this invention will become apparent to those skilled in
the art from the further disclosure of this invention to
be made in the following detailed description of a preferred
embodiment and described in the appended claims and various
advantages not referred to herein will become obvious to
those of ordinary skill in the art through employment of
the invention in practice.
Now a preferred embodiment of the invention will be
described below in conjunction with concrete experiments.
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retailed Description of Preferred Embodiments:
A method for the manufacture of a wiper blade according
to the present invention will be described. First, a lopper
blade matrix Or a prescribed shape is molded of EM or EPDM
as the material. Then the wiper blade matrix so produced is
fluorinated to have fluorine atoms bonded to the carbon atoms
forming the main chain of the saturated organic high molecular
compound (EM or EPDM) in the surface layer of the wiper blade
matrix.
In the EM so used, the ethylene content falls in the
range of 75 to 50% by weight and the propylene content in the
range of 25 to 50% by weight. In the EPDM, the ethylene and
propylene contents are in the ranges mentioned above and the
dine content is in a minute proportion. Here, the fluorination
may be effected in the form of a gaseous-phase reaction or a
liquid-phase reaction. The gaseous-phase reaction can be
carried our by a method of directly exposing the wiper blade
matrix fresh from the molding step to an atmosphere solely Or
fluorine gas, an atmosphere formed of fluorine gas mixed with
a small amount Or oxygen gas, or an atmosphere prepared by
diluting fluorine gas or a mixture of fluorine gas and
a small amount of oxygen was with an
inert gas such as helium, Argo nor nitrogen. The reaction of this
method is ~errormed at a fluorine concentration of 5 to 100%,
preferably about 10%, at a temperature in the range of 0 to
100C. An excessively high fluorine concentration is undesirable
because cracks occur easily on the surface of the
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wiper blade. As means of effecting the liquid-phase treatment,
the method which comprises immersing a wiper blade matrix fresh
from the molding step into a fluorine type solvent obtained by
dispersing fluorine gas in perfluorohexane, for example, may
be used.
To promote the fluorination, the treatment by either of
the methods described above may be carried out with
irradiation of ultraviolet light or some
other radiant ray. Otherwise, the treatment may be performed
in combination with a treatment using plasma.
The wiper blade of this invention which is obtained as
described above has the surface layer portion thereof
fluorinated substantially completely.-
Next, examples served to compare the wiper blade of the present invention with the conventional wiper blade in
various properties will be illustrated below.
Example 1 ]
Wiper blade matrices for an automobile were molded
severally of EM and EPDM as raw materials and fluorinated in
a mixed gas of 90% try volume) of nitrogen and 10% of fluorine
at 40C for 40 minutes to obtain wiper blades according to
this invention. Separately, a wiper blade matrix was molded
of natural rubber and chlorinated to obtain a conventional
wiper blade.
With regard to the wiper blades of the present invention
and the conventional wiper blade so prepared wiping durability
test was carried out and the coefficient of friction was
measured. The results are shown in Table 1.
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The specification of the wiping durability test is as follows:
a sample wiper blade lOOrDrn in length was reciprocated on a flat sheet
glass at 45 strokes per minute under the conditions Or 155 g of arm
pressure and 150 morn of stroke length, at one cycle of Srninutes
consisting of water sprinting for 4 minutes and no water sprinkling for
1 minutes. The friction coefficient (~) was
measured on the sample in a dry state. In Table 1, A
represents the conventional wiper blade involving chlorination
of natural rubber, B the wiper blade involving fluorination
of END and C the wiper blade involving fluorination of EM,
respectively.
[Table 1 Friction coefficient l
Number of blade A B
reciprocations
0 0.750.44 0.45
10,000 1.540.44 owe
50,000 1.960.45 owe
100,000 owe 0.50
300,000 2.010.65 0.72
500,000 2.040.91 1.01
It us noted from Table 1 that the wiper blades according
to this invention shows extremely small friction coefficients
us at all the indicated steps between 0 and 500,000 times of respire-
cation strokes of the durability test as compared with the conventional
wiper blade. The result indicates that they possess durability several tens
of times higher than the durability of the conventional wiper
blade.
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[Example 2]
Similarly to Example 1, wiper blades according to
the present invention were prepared by using EM and EPDM as
raw materials and performing fluorination and a conventional
wiper blade by using natural rubber as a raw material and
performing chlorination. These wiper blades were tested with
a cut body for durability rated by amount of abrasion (mm3) per
unit length (1 cm). The results are summarized in Table 2.
In the cut-body wiping durability test, a sample wiper
blade 450 mm in length was reciprocated at 45 strokes per minute
under the condition of 700 g of arm pressure, at one cycle of 5
minutes consisting of a spray with water for 4 minutes, no spray
with water for 0.5 minutes and no driving for 0.5 minutes.
In Table 2,
A through C have the same meanings as described above.
[Table 2 Amount of abrasion (mm3/cm)]
Length of' durability A C
_
50 h 0.110 oily 0.053
t 100 h 0.217 0.082 0.090
150 h 0.302 0.107 0.115
t 200 h 0.406 0.164 0.180
It is noted from Table 2 that the amounts of abrasion
of the wiper blades according to this invention
after 200 hours of test were substantially equal to the amount
of abrasion ox the conventional wiper blade after 50
hours of test. The results show that the wiper blades of
this invention involving fluorination are superior to the conventional
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wiper blade involving chlorination m terms of abrasion resistance.
[Example 3]
Similarly to Example 1, wiper blades according to
this invention were prepared by molding wiser blade matrices
severally of EM and EPDM and fluoridating these wiper blade
matrices and a conventional wiper blade was prepared by
molding a wiper blade matrix of natural rubber and chlorinating
the wiper blade. These wiper blades were tested for weather-
ability with Sun shining Weather-meter~and then tested for wiping
durability. The results are shown in Table 3.
In the weather test with the Sun shining Wé~ther-~eter, a
sample wiper blade was left standing at a black panel-temper-
azure of 63 1 3C for 48 hours, with irradiation for 120 minutes
and a spray for 18 minutes in each cycle, by following the
method of JIG B7753 (Sunshine carbon-arc type weather test)
with necessary modifications. In Table 3, A through C have
the same meanings as indicated above.
table 3 Friction coefficient after weather test l
Number of blade _ I _ C
reciprocations A I B
0 1.10 0.45 0.45
10,000 1.75 0.45 owe
50,000 2.05 0.45 owe
100,000 2.07 owe 0.50
300,000 2.07 owe 0.69
~00,000 owe 0.90 1.01
It is noted from Table 3 that even after the weather
test, the wiper blades obtained by using saturated organic high
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molecular compounds and performing fluorination show
substantially the same friction coefficients as before the
test. The results indicate that the wiper blades of this
invention are superior to the conventional wiper blade in weather ability.
example 4]
Similarly to Example l, wiper blades according to
the present invention were prepared by using EM and EPDM
severally as raw materials and performing fluorination and a
conventional wiper blade was prepared by using natural rubber
and performing chlorination. These wiper blades were left
standing as stretched to 120% of the original length in an
atmosphere kept at 40C with an ozone concentration of 50 ppm.
After the standing, they were visually examined for occurrence
of cracks. The results are shown in Table 4. In Table 4,
A through C have the same meanings as indicated above.
[Table 4 Occurrence of cracks]
wiper blade _ __ _ _
_ . . ___
Occurrence Large crack No crack No crack
of cracks occurred even occurred even occurred even
crier 96 hours asker 2000 hours after 2000 hours
_ __ of' standing of standing of standing
It is noted from Table 4 that the wiper blades obtained
by using Err and EPDM and performing fluorination are superior to
the conventional wiper blade in terms of resistance to ozone.
[Example 5]
Similarly to Example l, wiper blades according to the
present invention were prepared by using EM and EPDM separately
-` ~2330~)
as raw materials and performing fluorination, and a conventional
wiper blade was prepped by using natural rubber and performing
chlorination. With respect to these wiper blades, a permanent
set test was conducted by compressing the wiper blades with
a load of 15.5 Kg/cm at 100c for 72 hours. The results
are shown in Table 5. In Table 5, A through C have the same
meanings as indicated above.
[Table 5 an angle of a permanent set]
wiper blade A B C
and, angle ,
of deformation 52 22 11
Jo -
It it noted from Table 5 that the wiper blades of this
invention are extremely excellent in a permanent set resistance
as compared with the conventional wiper blade.
- As described above, the present invention produces a
wiper blade by molding a wiper blade matrix of EM or EPDM
and flurorinatin~ the wiper blade matrix thereby causing
fluorine atoms to be bonded through substitution to the carbon
atoms forming the main chain of EM or END The wiper blade
so produced, therefore, shows a notably small friction coefficient
and is excellent in resistance to aging, abrasion, ozone,
and permanent set, and in weatherabilit~ as compared with
the conventional wiper blade.
Plainly many modifications and variations of the present
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invention are possible in light of the preceding teachings.
It is, therefore, to be understood that within the scope
of the appended claims, the present invention may be practiced
otherwise than as specifically described herein.
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