GB2154864A

GB2154864A - Wiper blade

Info

Publication number: GB2154864A
Application number: GB08505132A
Authority: GB
Inventors: Hiroshi Yoshida; Izuma Nishimura; Sumihiko Yagenji; Hiroshi Kuramochi
Original assignee: Honda Motor Co Ltd; Kokoku Rubber Industry Co Ltd
Current assignee: Honda Motor Co Ltd; Kokoku Rubber Industry Co Ltd
Priority date: 1984-03-02
Filing date: 1985-02-28
Publication date: 1985-09-18
Also published as: FR2560602B1; DE3506766A1; GB2154864B; GB8505132D0; JPS60184531A; DE3506766C2; FR2560602A1; CA1233010A

Abstract

A wiper blade is produced by molding a wiper blade matrix of ethylene-propylene copolymer (EPM) or ethylene-propylene-diene copolymer (EPDM) and fluorinating the matrix thereby causing fluorine atoms to be bonded to the carbon atoms of the copolymer in the surface layer of the matrix. The wiper blade possesses a low friction coefficient and is resistant to ageing, ozone, chemicals, and permanent set.

Description

SPECIFICATION Wiper blades This invention relates to wiper blades for wiping the windscreens of vehicles such as automobiles, public service vehicles, heavy goods vehicles, railway locomotives or aircraft.

The wiper blades used for vehicles are intended to wipe water drops, snow, etc. away from the windscreen surface by sliding on the windscreen surface. It is, therefore, required to give even wiping to windscreens by ensuring that the wiper blades are pressed uniformly against the windscreens, and it is desirable that smooth operation, avoiding emission of objectionable noise, should be obtained by offering low frictional resistance.With these ends in mind, it has been customary to form wiper blades from natural rubber, synthetic rubber such as chloroprene rubber, thermoplastic elastomer such as urethane type elastomer, or synthetic resin such as polyethylene thereby to confer upon a wiper blade elasticity high enough for the wiper blade to slide evenly on a screen surface and, at the same time, to subject the surface of the wiper blade to a treatment of chlorination or bromination thereby to cause bonding of chloride atoms or bromine atoms to the carbon atoms in the main chain of the rubber or elastomer and induce degradation of frictional resistance. A treatment of chlorination or bromination, however, is incapable of amply lowering the frictional resistance.Particularly, the C-CI bond or C-Br bond is chemically instable and is readily unbonded by heat, water, ultraviolet light, ozone, oxygen, or chemicals to remove Cl or Br. 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 referred to as EPM) and the ethylene-propylenediene copolymer (hereinafter referred to as EPDM) obtained by adding a small amount of a diene compound to EPM for enhancing its vulcanizability have a remarkable quality in resistance to ageing, ozone, chemicals, water and permanent set. The above-mentioned problems, therefore, can be solved, if EPM or EPDM may be used as a material for the wiper blade.

Since EPM and EPDM are saturated organic high molecular compounds possessing no double bond in the main chains thereof, however, they form neither C-CI bond npr C-Br bond even if they are subjected to the treatment of chlorination or bromination.

The present invention is accomplished by studying the fact that fluorine is extremely active and substitutes for the hydrogen atom of the C-H bond to form a C-F bond.

According to this invention, it is provided that a wiper blade is produced by molding a wiper blade matrix of ethylene-propylene copolymer (EPM) or ethylene-propylene-diene copolymer (EPDM) and fluorinating the wiper blade matrix to cause 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 that ia excellent in resistance to ageing, 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 specific experiments.

A method for the manufacture of a wiper blade according to the present invention will be described. First, a wiper blade matrix of a prescribed shape is molded of EPM 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 (EPM or EPDM) in the surface layer of the wiper blade matrix.

In the EPM 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 diene 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 of fluorine gas, an atmosphere formed of fluorine gas mixed with a small amount of oxygen gas, or an atmosphere prepared by diluting fluorine gas or a mixture of fluorine gas and a small amount of oxygen gas with an inert gas such as helium, argon, or nitrogen.The reaction of this method is performed at a fluorine concentration of 5 to 100%, preferably about 10%, at a temperature in the range of 0 to 1 00'C. An excessively high fluorine concentration is undesirable because cracks occur easily on the surface of the 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 serving 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 EPM and EPDM as raw materials and fluorinated in a mixed gas of 90% (by volume) of nitrogen and 10% of fluorine at 40 C 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.

The specification of the wiping durability test was as follows: a sample wiper blade 100 mm in length was reciprocated on a flat sheet of glass at 45 strokes per minute under the conditions of 155 g of arm pressure and 150 mm of stroke length, at one cycle of 5 minutes consisting of water sprinkling for 4 minutes and no water sprinkling for 1 minute. The friction coefficient (tic) 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 EPDM, and C the wiper blade involving fluorination of EPM, respectively.

Table 1 Friction coefficient #) Number of blade reciprocations A B C 0 0.75 0.44 0.45 10.000 1.54 0.44 0.46 50,000 1.96 0.45 0.46 100,000 1.99 0.48 0.50 300,000 2.01 0.65 0.72 500,000 2.04 0.91 1.01 It is noted from Table 1 that the wiper blades according to this invention show extremely small friction coefficients (,u) at all the indicated steps between 0 and 500,000 times of reciprocation 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.

Example 2 Similarly to Example 1, wiper blades according to the present invention were prepared by using EPM 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 (10mm). 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, B and C have the same meanings as described above.

Table 2 Amount of abrasion (mm3/cm) Length of durability A B C 50 h 0.110 0.049 0.053 100 h 0.217 0.082 0.090 150 h 0.302 0.107 0.115 200 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 of 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 wiper blade involving chlorination in terms of abrasion resistance.

Example 3 Similarly to Example 1, wiper blades according to this invention were prepared by molding wiper blade matrices severally of EPM and EPDM and fluorinating 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 weatherability with Sunshining Weather-meter and then tested for wiping durability. The results are shown in Table 3.

In the weater test with the Sunshining Weather-meter, a sample wiper blade was left standing at a black panel temperature of 63 i 3 C for 48 hours, with irradiation for 120 minutes and a spray for 18 minutes in each cycle, by following the method JIS B7753 (Sunshine carbon-arc type weather test) with necessary modifications. In Table 3, A, B and C have the same meanings as indicated above.

Table 3 Friction coefficient after weather test (v) Number of blade reciprocations A B C 0 1.10 0.45 0.45 10,000 1.75 0.45 0.46 50,000 2.05 0.45 0.46 100,000 2.07 0.48 0.50 300,000 2.07 0.66 0.69 500,000 2.08 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 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 weatherability.

Example 4 Similarly to Example 1, wiper blades according to the present invention were prepared by using EPM 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 40 C 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, B and C have the same meanings as indicated above.

Table 4 Occurrence of cracks Type of wiper blade A B C Occurrence Large crack No crack No crack of cracks occurred occurred even occurred even after 96 hours after 2000 hours after 2000 hours of standing of standing of standing It is noted from Table 4 that the wiper blades obtained by using EPM and EPDM and performing fluorination are superior to the conventional wiper blade in terms of resistance to ozone.

Example 5 Similarly to Example 1, wiper blades according to the present invention were prepared by using EPM and EPDM separately as raw materials and performing fluorination, and a conventional wiper blade was prepared 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 100 C for 72 hours. The results are shown in Table 5. In Table 5, A, B and C have the same meanings as indicated above.

Table 5 an angle of a permanent set Type of wiper blade A B C Angle of deformation 52' 22 11 It is 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 EPM or EPDM and flurorinating the wiper blade matrix thereby causing fluorine atoms to be bonded through substitution to the carbon atoms forming the main chain of EPM or EPDM. The wiper blade so produced shows a notably small friction coefficient and is excellent in resistance to ageing abrasion, ozone, and permanent set, and in weatherability as compared with the conventional wiper blade.

Plainly many modifications and variations of the present 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 practised otherwise than as specifically described herein.

Claims

1. A wiper blade produced by molding a wiper blade matrix of ethylene-propylene copolymer (EPM) or ethylene-propylene-diene copolymer (EPDM) and fluorinating the wiper blade matrix to cause fluorine atoms to be bonded to the carbon atoms of the copolymer in the surface layer of the wiper blade matrix.

2. A wiper blade as claimed in claim 1, wherein the fluorination is carried out in a fluorine gas-containing atmosphere.

3. A wiper blade as claimed in claim 2, wherein the fluorine gas-containing atmosphere is an atmosphere formed solely of fluorine gas.

4. A wiper blade as claimed in claim 2, wherein the fluorine gas-containing atmosphere is an atmosphere of fluorine gas mixed with a small amount of oxygen gas.

5. A wiper blade as claimed in claim 3 or 4, wherein the fluorine gas-containing atmosphere is diluted with an inert gas.

6. A wiper blade as claimed in any one of the preceding claims, wherein the fluorination is carried out at a fluorine concentration in the range of 5 to 100%.

7. A wiper blade as claimed in claim 6, wherein the fluorine concentration is about 10%.

8. A wiper blade as claimed in any one of the preceding claims, wherein the fluorination is carried out at a temperature in the range of 0 to 100 C.

9. A wiper blade as claimed in claim 8, wherein the temperature is about 40 C.

10. A wiper blade as claimed in any one of the preceding claims, wherein fluorination is carried out in a fluorine type solvent prepared by dispersing fluorine gas in a solvent.

11. A wiper blade as claimed in claim 10, wherein the solvent is perfluorohexane.

12. A wiper blade as claimed in any one of the preceding claims, wherein the ethylenepropylene copolymer has an ethylene content in the range of 75 to 50% by weight, and a propylene content in the range of 25 to 50% by weight.

13. A wiper blade produced as claimed in claim 1 and substantially in accordance with any one of the foregoing examples.