Wiper blade rubber

Abstract

The present invention comprises a rubber composition that contains carbon black and is such that a polymer thereof is a rubber blend containing natural rubber and chloroprene rubber. A coating layer (14) of a fixed lubricant is provided on at least a lip part (12). The coating layer contains a binder and the fixed lubricant, has a thickness of 1.5 μm to 5 μm, and is such that the ratio of a portion not covered by the fixed lubricant to the total area of the coating layer in the lip part of 1% or less. A maximum void size at one location of the portion not covered by the fixed lubricant in the coating layer is smaller than 600 μm2. This thereby prevents a rise in the coefficient of friction during semi-dry conditions and suppresses generation of abnormal noise at the time of drying.

Description

Wiper blade rubber

[0001] This invention relates to wiper blade rubber used in automobile windshields and the like.

[0002] Conventionally, as shown in Patent Document 1, for example, a wiper blade rubber having a lip portion on which a coating layer is provided by spray application to a rubber substrate is known, wherein when the spray-coated painted surface is observed, the coating layer consists of a portion that covers the rubber substrate and a portion that does not cover the rubber substrate, and the portion that does not cover the rubber substrate consists of a plurality of holes with a diameter of 10 μm to 40 μm that are evenly formed throughout the entire surface of the coating layer without any significant bias, and these holes penetrate from the surface on which the coating layer is in contact with the rubber substrate to the outer surface of the coating layer, and the ratio of the total area of ​​the portion that covers the rubber substrate to the total area of ​​the portion that does not cover the rubber substrate is known to be 40:60 to 60:40.

[0003] This blade rubber design incorporates areas that are not covered by the rubber base material, thereby suppressing bleed-out from the rubber base material and the occurrence of blistering (blistering) of the coating layer due to bloom.

[0004] Patent No. 6937307

[0005] However, in the wiper blade rubber of Patent Document 1, the proportion of the area not covered by the rubber base material is increased, which can increase the coefficient of friction when semi-dry, causing abnormal noises as it dries. For example, when driving in the rain and the wipers are activated, if the vehicle enters a tunnel, the rainwater will disappear from the wiped area of ​​the wiper blade rubber after several wipes. However, as the rainwater is almost gone, the wiper blade rubber will activate, causing abnormal noises that may be unpleasant for the occupants.

[0006] This disclosure has been made in view of the above, and its purpose is to prevent an increase in the coefficient of friction during semi-drying and to suppress the generation of abnormal noise as the surface dries.

[0007] To achieve the above objectives, this disclosure adjusts the ratio of the portion of the lip that is not covered by the solid lubricant coating layer.

[0008] Specifically, in the first embodiment, the polymer is a blended rubber containing natural rubber and chloroprene rubber, and is made of a rubber composition containing carbon black, with a solid lubricant coating layer provided at least on the lip portion, the coating layer comprising a binder and a solid lubricant, having a thickness of 1.5 μm or more and 5 μm or less, the ratio of the portion not covered by the solid lubricant being 1% or less of the total area of ​​the coating layer on the lip portion, and the maximum void size of one location in the portion not covered by the solid lubricant in the coating layer being 600 μm ２ It is smaller than that.

[0009] Here, if the coating layer is thinner than 1.5 μm, abnormal noises are more likely to occur as it dries, and if it is thicker than 5 μm, the wiping performance after durability deteriorates.

[0010] Maximum void size: 600 μm ２ As a result, abnormal noises are more likely to occur as the paint dries.

[0011] If the proportion of the area not covered by the solid lubricant is greater than 1% of the total surface area of ​​the coating layer on the lip, an abnormal noise will occur as it dries.

[0012] However, with the above configuration, by maintaining an appropriate thickness of the coating layer and appropriately controlling the proportion of the coating layer that is not covered by the solid lubricant and the maximum void size, a wiper blade rubber can be obtained that prevents an increase in the coefficient of friction during semi-drying and suppresses the generation of abnormal noise as it dries.

[0013] In a second embodiment, in the first embodiment, the binder is thermoplastic polyurethane, and the solid lubricant is artificial graphite powder.

[0014] According to the above configuration, a stable coating layer with high quality that is resistant to peeling can be obtained.

[0015] In the third embodiment, in the first or second embodiment, the average particle size of the artificial graphite powder of the solid lubricant is 10 μm or less.

[0016] According to the above configuration, the proportion of the area not covered by the solid lubricant is less than 1%, but if it exceeds 10 μm, it exceeds 1%, and abnormal noise occurs when it dries.

[0017] As explained above, this disclosure makes it possible to prevent an increase in the coefficient of friction during semi-drying and suppress the generation of abnormal noises as the surface dries.

[0018] This is a perspective view showing the appearance of the wiper blade rubber. The first is a magnified photograph of the surface when the proportion of the area not covered by solid lubricant is 1% or less of the total surface area of ​​the coating layer on the lip. The second is a magnified photograph of the surface when the proportion of the area not covered by solid lubricant is greater than 1% of the total surface area of ​​the coating layer on the lip.

[0019] The embodiments of this disclosure will be described below with reference to the drawings.

[0020] Figure 1 shows a wiper blade rubber 10 according to an embodiment. This wiper blade rubber 10 is a generally flat, elongated rubber component, with a mounting and holding portion 11 on one side in the vertical direction and a lip portion 12 on the other side in the vertical direction, and a neck portion 13 connecting the mounting and holding portion and the lip portion 12. At least the area of ​​the outer circumference of the lip portion 12 that contacts the glass surface is provided with a solid lubricant coating layer 14.

[0021] In this embodiment, the wiper blade rubber 10 has a mounting and holding portion 11 that is attached and held to the vertebra of a wiper drive unit provided, for example, on the lower side of the windshield of an automobile. When the wiper drive unit is driven, the portion of the lip portion 12 with the coating layer 14 tilts with the neck portion 13 as a pivot point and slides in contact with the surface of the windshield, thereby wiping away rain and the like.

[0022] The wiper blade rubber 10 according to this embodiment is formed from a crosslinked rubber composition containing a rubber component and a rubber compounding agent.

[0023] Examples of rubber components include natural rubber (NR), chloroprene rubber (CR), ethylene propylene diene rubber (EPDM), and styrene butadiene rubber (SBR). Examples of CR include sulfur-modified type, mercaptan-modified type, and xanthogene-modified type. The rubber component preferably contains one or more of these, and a blended rubber containing NR and CR is more preferable from the viewpoint of obtaining excellent wiping and sliding properties, as described later. When the rubber component is a blended rubber containing NR and CR, the NR content is preferably less than the CR content from the same viewpoint. From the same viewpoint, the mass ratio of the NR content to the CR content is preferably 30 / 70 or more and less than 50 / 50, more preferably 35 / 65 or more and 45 / 55 or less.

[0024] Examples of rubber compounding agents include carbon black, vulcanization accelerators, processing aids, vulcanization accelerators, and antioxidants.

[0025] Examples of carbon black include channel black, furnace black, thermal black, and acetylene black. Examples of furnace black include SAF, ISAF, N-339, HAF, N-351, MAF, FEF, SRF, GPF, ECF, and N-234. Examples of thermal black include FT and MT. It is preferable that the carbon black contains one or more of these. The carbon black content in the crosslinked rubber composition is, for example, 20 parts by mass or more and 40 parts by mass or less per 100 parts by mass of rubber component. In this application, the content in the crosslinked rubber composition refers to the amount of the crosslinked rubber composition blended into the uncrosslinked rubber composition before crosslinking.

[0026] Examples of vulcanization accelerators include metal oxides such as zinc oxide (zinc oxide) and magnesium oxide, metal carbonates, fatty acids and their derivatives. The vulcanization accelerator preferably contains one or more of these, and from the viewpoint of obtaining excellent wiping and sliding properties, it is more preferable to contain a metal oxide, even more preferable to contain zinc oxide and / or magnesium oxide, and even more preferable to contain both zinc oxide and magnesium oxide. When the rubber component contains CR and the vulcanization accelerator contains a metal oxide, the metal oxide also acts as a crosslinking agent for CR. The content of the vulcanization accelerator in the crosslinked rubber composition is, for example, 3 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the rubber component.

[0027] Examples of processing aids include stearic acid, polyethylene wax, and metal salts of fatty acids. The processing aid preferably contains one or more of these, and more preferably contains stearic acid from the viewpoint of obtaining excellent wiping and sliding properties. The content of the processing aid in the crosslinked rubber composition is, for example, 0.5 parts by mass or more and 1.5 parts by mass or less per 100 parts by mass of the rubber component.

[0028] Examples of vulcanization accelerators include sulfenamide-based vulcanization accelerators, thiourea-based vulcanization accelerators, aldehyde-ammonia-based vulcanization accelerators, aldehyde-amine-based vulcanization accelerators, guanidine-based vulcanization accelerators, thiazole-based vulcanization accelerators, thiram-based vulcanization accelerators, and dithiocarbamate-based vulcanization accelerators. It is preferable that the vulcanization accelerator contains one or more of these. The content of the vulcanization accelerator in the crosslinked rubber composition is, for example, 2 parts by mass or more and 5 parts by mass or less per 100 parts by mass of the rubber component.

[0029] Examples of anti-aging agents include p-phenylenediamine-based anti-aging agents, diphenylamine-based anti-aging agents, amine-ketone-based anti-aging agents, monophenol-based anti-aging agents, bisphenol-based anti-aging agents, polyphenol-based anti-aging agents, benzimidazole-based anti-aging agents, dithiocarbamate-based anti-aging agents, phosphite-based anti-aging agents, and organic thioacid-based anti-aging agents. The anti-aging agent may contain one or more of these. The content of the anti-aging agent in the crosslinked rubber composition is, for example, 2 parts by mass or more and 6 parts by mass or less per 100 parts by mass of the rubber component.

[0030] From the viewpoint of obtaining excellent wiping and sliding properties, it is preferable that the crosslinked rubber composition is crosslinked using sulfur as the crosslinking agent. In this case, the amount of sulfur added to the uncrosslinked rubber composition is, for example, 1 to 4 parts by mass per 100 parts by mass of the rubber component. The crosslinked rubber composition may also be crosslinked using an organic peroxide as the crosslinking agent.

[0031] The coating agent for forming the coating layer comprises a solid lubricant and a binder for adhering the solid lubricant to the surface of the wiper blade rubber 10. The binder is prepared by mixing a urethane polymer with an organic solvent to a concentration of 1% by mass or less. The organic solvent may be ether-based, ketone-based, or ester-based. A mixture thereof may also be used.

[0032] As a solid lubricant, artificial graphite powder (for example, UF-G5 manufactured by RESONAC) is used. UF-G5 has a fixed carbon content of 98.0% by mass or more, an ash content of 1.0% by mass or less, a particle size of 3 μm, and a specific surface area of ​​40 m². ２ It has a density of 1 / g, contains fewer impurities than natural graphite, has stable quality, and provides high thermal conductivity, sliding properties, and lubricity that cannot be obtained with carbon black. It is desirable that the artificial graphite powder be contained in an amount of 2% to 7% by mass per 100% by mass of the organic solvent.

[0033] The organic solvent may be of ether type, ketone type, or ester type, but it is preferable to contain a urethane prepolymer for forming a binder (e.g., thermoplastic polyurethane) in an amount of 1% by mass or less based on 100% by mass of the organic solvent. Examples of the thermoplastic polyurethane include 119ATR manufactured by BASF.

[0034] -Coating Method- A graphite coating layer was formed on the coating layer 14 by spray-coating the coating agent with a spray nozzle onto portions corresponding to the contact sliding portions on both sides of the tandem molded body. At this time, the combination of the relative movement speed between the spray nozzle and the tandem molded body and the number of coating passes was varied to control the thickness of the graphite coating layer, the substrate exposure ratio, and the maximum area of uncovered portions.

[0035] -Coating Film Thickness Measurement- In a test piece of the wiper blade rubber 10, the tip sliding portion of the lip portion 12 was observed with a video microscope at 1000x magnification, and the thickness of the coating layer 14 formed on the tip sliding portion was measured.

[0036] -Substrate Exposure Ratio Measurement- The surface of the coating layer 14 was observed with a video microscope at 1000x magnification. A portion with a height of 0.5 µm or less was defined as the substrate, a portion higher than 0.5 µm was defined as a coated portion, and the area ratio of the uncoated substrate was calculated as the substrate exposure ratio. A portion that contains only the binder with no graphite present and has a height of 0.5 µm or less is recognized as the substrate.

[0037] -Durability Wiping Measurement- The durability wiping measurement is performed on the wiper blade rubber 10 in accordance with the procedure described in JIS D 5710. The wiper blade rubber 10 is attached in a normal usage state, water is uniformly sprinkled onto the glass surface at a sprinkling rate of 800 ml / min or more under an ambient temperature of 20±15°C and a water temperature of 38°C or lower, and 500,000 reciprocating operations are performed at a reciprocating operation speed of 45 times / min or more, then the number of unwiped areas is counted.

[0038] If the number of unwiped areas is less than that specified in JIS D 5710, the result is rated as "Good (○)", and if the number of unwiped areas is equal to or more than that specified, the result is rated as "Poor (×)".

[0039] -Abnormal Noise Evaluation- Similarly, in an actual vehicle, the arm pressure applied to a wiper arm fitted with a wiper blade rubber 10 was set to 16 gf / cm, and the wiper was driven for 5 minutes or more while spraying water at a rate of 800 ml / min or more. After 5 minutes, water spraying was stopped, the wiper was driven to perform 3 reciprocating motions, and it was checked whether abnormal noise occurred during reversal.

[0040] A rating of ○ was given when no abnormal noise occurred, and a rating of × was given when abnormal noise occurred.

[0041] For Examples 1 to 6 and Comparative Examples 1 to 4, wiper blade rubbers prepared under 10 different coating conditions from 1 to 10 were prepared, and the results of each of the above measurements are shown in Table 1. When the speed of Example 1 was set as 1 in terms of coating conditions, each speed is shown as a ratio. The number of coating applications was also varied.

[0042]

[0043] <Example 1> Under coating conditions of a speed of 1 and 6 coating applications, the coating film thickness was 2.5 μm, and the maximum area of uncoated portions was 200 μm ２ , the average particle diameter of the graphite powder was 3 μm, and the base material ratio (area ratio) was 0.4%. In Example 1, no abnormal noise occurred, and there was no problem in the durable wiping test.

[0044] <Example 2> Under coating conditions of a speed of 1 and 10 coating applications, the coating film thickness was 3.0 μm, and the maximum area of uncoated portions was 100 μm ２ , the average particle diameter of the graphite powder was 3 μm, and the base material ratio (area ratio) was 0.3%. In Example 2 as well, no abnormal noise occurred, and there was no problem in the durable wiping test.

[0045] <Example 3> Under coating conditions of a speed of 1 and 2 coating applications, the coating film thickness was 1.5 μm, and the maximum area of uncoated portions was 400 μm ２ , the average particle diameter of the graphite powder was 3 μm, and the base material ratio (area ratio) was 1.0%. In Example 3 as well, no abnormal noise occurred, and there was no problem in the durable wiping test.

[0046] <Example 4> Under coating conditions of a speed of 1 / 3 and 5 coating applications, the coating film thickness was 5.0 μm, and the maximum area of uncoated portions was 20 μm ２, the average particle diameter of the graphite powder was 3 μm, and the base material ratio (area ratio) was 0.2%. In Example 4, abnormal noise did not occur, and there was also no problem in the durability wiping test.

[0047] <Example 5> Under the coating conditions of speed 1 and 6 coating times, the coating film thickness was 3.5 μm, and the maximum area of the uncoated portion was 310 μm ２ , the average particle diameter of the graphite powder was 5 μm, and the base material ratio (area ratio) was 0.6%. In Example 5, abnormal noise did not occur, and there was also no problem in the durability wiping test.

[0048] <Example 6> Under the coating conditions of speed 1 and 6 coating times, the coating film thickness was 4.5 μm, and the maximum area of the uncoated portion was 530 μm ２ , the average particle diameter of the graphite powder was 10 μm, and the base material ratio (area ratio) was 0.9%. In Example 6, abnormal noise did not occur, and there was also no problem in the durability wiping test. That is, there was no problem if the average particle diameter of the graphite powder was 10 μm or less.

[0049] <Comparative Example 1> Under the coating conditions of speed 1 / 3 and 2 coating times, the coating film thickness was 2.5 μm, and the maximum area of the uncoated portion was 600 μm ２ , the average particle diameter of the graphite powder was 3 μm, and the base material ratio (area ratio) was 1.0%. In Comparative Example 1, although there was no problem in the durability wiping test, abnormal noise occurred.

[0050] <Comparative Example 2> Under the coating conditions of speed 1 and 1 coating time, the coating film thickness was 0.5 μm, and the maximum area of the uncoated portion was 800 μm ２ , the average particle diameter of the graphite powder was 3 μm, and the base material ratio (area ratio) was 10.0%. In Comparative Example 2, abnormal noise occurred, and a large amount of unwiped residue also occurred in the durability wiping test.

[0051] <Comparative Example 3> Under the coating conditions of speed 1 and 14 coating times, the coating film thickness was 6.0 μm, and the maximum area of the uncoated portion was 10 μm ２ , the average particle diameter of the graphite powder was 3 μm, and the base material ratio (area ratio) was 0.1%. In Comparative Example 3, although abnormal noise did not occur, a large amount of unwiped residue occurred in the durability wiping test.

[0052] <Comparative Example 4> Under the coating conditions of speed 1 and 6 coating times, the coating film thickness was 7.0 μm, and the maximum area of the uncoated portion was 850 μm ２The average particle size of the graphite powder was set to 25 μm, and the substrate ratio (area ratio) was set to 3.2%. In Comparative Example 4, the particle size became 25 μm, making it difficult to lay the material without gaps, resulting in a larger area ratio and the generation of abnormal noise. Furthermore, the film thickness also increased, resulting in many residues remaining even after wiping following the durability test.

[0053] As can be seen from the comparison between the examples and comparative examples above, if the thickness of the coating layer is less than 1.5 μm, abnormal noises are more likely to occur when the coating is drying during inversion, and if it is thicker than 5 μm, durability decreases.

[0054] Maximum void size: 600 μm ２ As a result, abnormal noises are more likely to occur as the paint dries.

[0055] If the area ratio of the portion not covered by the fixing lubricant (base material ratio) is greater than 1% of the total area of ​​the coating layer on the lip portion, an abnormal noise will occur as it dries.

[0056] However, as shown in Examples 1 to 6, the thickness of the coating layer 14 is 1.5 μm or more and 5 μm or less, the proportion of the area not covered by flake-like graphite is 1% or less of the total area of ​​the coating layer 14 in the lip portion 12, and the maximum void size of one location in the area not covered by flake-like graphite in the coating layer 14 is 600 μm. ２ When the size is smaller than this, the thickness of the coating layer is kept at an appropriate level, and the proportion of the coating layer that is not covered by flaky graphite and the maximum void size are appropriately maintained, resulting in a wiper blade rubber that prevents an increase in the coefficient of friction when semi-dry and suppresses the generation of abnormal noise as it dries.

[0057] As explained above, this disclosure makes it possible to prevent an increase in the coefficient of friction during the semi-drying stage as the surface dries, thereby suppressing the generation of abnormal noises during the drying stage.

[0058] The embodiments described above are essentially preferred examples and are not intended to limit the scope of the present invention, its applications, or uses.

[0059] 10 Wiper blade rubber 11 Mounting and holding part 12 Lip part 13 Neck part 14 Coating layer

Claims

1. The polymer is a blended rubber containing natural rubber and chloroprene rubber, and is made of a rubber composition containing carbon black, with at least the lip portion having a solid lubricant coating layer, the coating layer comprising a binder and a solid lubricant, having a thickness of 1.5 μm or more and 5 μm or less, the ratio of the portion not covered by the solid lubricant being 1% or less of the total area of ​​the coating layer on the lip portion, and the maximum void size of one location in the portion not covered by the solid lubricant in the coating layer being 600 μm. ２ A wiper blade rubber characterized by being smaller than [this].

2. The wiper blade rubber according to claim 1, characterized in that the binder is thermoplastic polyurethane and the solid lubricant is artificial graphite powder.

3. The wiper blade rubber according to claim 1, characterized in that the average particle size of the artificial graphite powder of the solid lubricant is 10 μm or less.

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