Wiper blade rubber

Abstract

A wiper blade rubber (10) is formed of a crosslinked rubber composition containing a rubber component and carbon black. The nitrogen adsorption specific surface area of the carbon black is 20 m2 / g or more and 40 m2 / g or less. The content of the carbon black in the crosslinked rubber composition is 15 parts by mass or more and less than 30 parts by mass with respect to 100 parts by mass of the rubber component. When the loss tangents of the viscoelastic characteristics of the crosslinked rubber composition at -20°C, -25°C, and -30°C are defined as tanδ (-20°C), tanδ (-25°C), and tanδ (-30°C), respectively, tanδ (-20°C) ≤ 1.0, tanδ (-25°C) ≥ 0.7, and tanδ (-30°C) ≥ 0.6 are satisfied.

Description

wiper blade rubber

[0001] The present invention relates to a wiper blade rubber.

[0002] Crosslinked rubber compositions for wiper blade rubbers containing carbon black SRF are known. For example, Patent Document 1 discloses a crosslinked rubber composition for wiper blade rubber containing 40 to 80 parts by mass of SRF added to 100 parts by mass of EPDM rubber. Patent Document 2 discloses a crosslinked rubber composition for wiper blade rubber containing 30 parts by mass of SRF added to 100 parts by mass of CR rubber. Patent Document 3 discloses a crosslinked rubber composition for wiper blade rubber containing 50 parts by mass of SRF added to 100 parts by mass of EPDM rubber.

[0003] Japanese Patent No. 6371900 Japanese Patent No. 5729877 Japanese Patent Laid-Open No. 2012-140090

[0004] The present invention relates to a wiper blade rubber formed of a crosslinked rubber composition containing a rubber component and carbon black, wherein the carbon black has a nitrogen adsorption specific surface area of ​​20 m ２ / g or more 40m ２ / g or less, the content of the carbon black in the crosslinked rubber composition is 15 parts by mass or more and less than 30 parts by mass per 100 parts by mass of the rubber component, and when the loss tangent at -20°C of the crosslinked rubber composition is tanδ(-20°C), the loss tangent at -25°C is tanδ(-25°C), and the loss tangent at -30°C is tanδ(-30°C), the viscoelastic properties of the crosslinked rubber composition satisfy tanδ(-20°C)≦1.0, tanδ(-25°C)≧0.7, and tanδ(-30°C)≧0.6.

[0005] FIG. 2 is a perspective view of a piece of wiper blade rubber according to an embodiment.

[0006] The embodiments will be described in detail below.

[0007] FIG. 1 shows a wiper blade rubber 10 according to an embodiment.

[0008] The wiper blade rubber 10 according to the embodiment is a long, thin rubber part having a roughly flat, plate-like shape, and has an attachment / holding portion 11 with an H-shaped cross section on one side in the width direction, and a lip portion 12 with a roughly triangular cross section on the other side in the width direction, and a thin-walled neck portion 13 connecting the attachment / holding portion and the lip portion.

[0009] The wiper blade rubber 10 of this embodiment has an attachment and holding portion 11 attached to a vertebra of a wiper drive unit provided, for example, on the underside of the windshield of an automobile, and when the wiper drive unit is driven, the lip portion 12 tilts with the neck portion 13 as a fulcrum, and the edge portion 14 at the tip of the lip portion 12 comes into contact with and slides against the surface of the windshield to wipe away rain, etc.

[0010] The wiper blade rubber 10 according to the embodiment is made of a rubber component and a nitrogen adsorption specific surface area of ​​20 m ２ / g or more 40m ２ / g or less (hereinafter referred to as "carbon black A") and a crosslinked rubber composition (hereinafter referred to as "crosslinked rubber composition X").

[0011] Examples of the rubber component include natural rubber (NR), chloroprene rubber (CR), ethylene propylene diene rubber (EPDM), and styrene butadiene rubber (SBR). Examples of CR include sulfur-modified, mercaptan-modified, and xanthogen-modified types. The rubber component preferably contains one or more of these, and from the viewpoint of suppressing hardening in a low-temperature atmosphere, a blend rubber containing NR and CR is more preferred.

[0012] When the rubber component contains NR, the Mooney viscosity of the NR is preferably 50 ML / s or less from the viewpoint of suppressing hardening in a low-temperature atmosphere. １＋４ (100℃) or more 80ML １＋４ (100°C) or less, more preferably 55ML １＋４ (100℃) or more 65ML １＋４ (100°C) or less. The Mooney viscosity is measured in accordance with JIS K6300-1:2013 (the same applies hereinafter).

[0013] When the rubber component contains CR, the CR is preferably a mercaptan-modified type. The Mooney viscosity of the CR is preferably 40 ML / s from the viewpoint of suppressing hardening in a low-temperature atmosphere. １＋４ (100℃) or more 60ML １＋４ (100°C) or less, more preferably 45ML １＋４ (100℃) or more 53ML １＋４ (100°C) or less.

[0014] When the rubber component is a blend rubber containing NR and CR, the NR content is preferably greater than the CR content from the viewpoint of suppressing hardening in a low-temperature atmosphere. From the same viewpoint as above, the mass ratio of the NR content to the CR content (NR / CR) is preferably greater than 50 / 50 and not more than 70 / 30, more preferably 55 / 45 or more and not more than 65 / 35.

[0015] Carbon black A is, for example, SRF (Semi Reinforcing Furnace, ASTM number N700 series, nitrogen adsorption specific surface area 27 m ２ / g), GPF (General Purpose Furnace, ASTM number N600 series, nitrogen adsorption specific surface area is 27 m ２ / g). Carbon black A preferably contains SRF and / or GPF, and more preferably contains SRF from the viewpoint of suppressing curing in a low-temperature atmosphere. The nitrogen adsorption specific surface area of ​​these carbon blacks is measured in accordance with JIS K6217-2:2017.

[0016] The nitrogen adsorption specific surface area of ​​carbon black A is 20 m ２ / g or more 40m ２ / g or less, but from the viewpoint of suppressing hardening in a low temperature atmosphere, it is preferably 25 m ２ / g or more 30m ２ / g or less.

[0017] The arithmetic mean particle diameter of carbon black A is preferably 50 nm to 100 nm, more preferably 65 nm to 70 nm, from the viewpoint of suppressing curing in a low-temperature atmosphere. This arithmetic mean particle diameter is determined by observing the carbon black under an electron microscope. Carbon black forms an aggregate structure in which fine particles are linked together. The particle diameter here is the primary particle diameter measured by regarding the fine particle portion as a single particle (primary particle) and approximating its diameter to a perfect circle. This primary particle diameter is measured by taking an electron microscope image of the carbon black and approximating it to a perfect circle. The arithmetic mean particle diameter dn is the average of the primary particle diameters and is determined by dn = (Σnidi) / (Σni).

[0018] The content of carbon black A in crosslinked rubber composition X is 15 parts by mass or more and less than 30 parts by mass per 100 parts by mass of the rubber component, but from the viewpoint of suppressing curing in a low-temperature atmosphere, it is preferably 18 parts by mass or more and 29 parts by mass or less, more preferably 20 parts by mass or more and 28 parts by mass or less, and even more preferably 26 parts by mass or more and 28 parts by mass or less. Note that the content in crosslinked rubber composition X in the present application means the amount blended into uncrosslinked rubber composition X' before crosslinking of crosslinked rubber composition X.

[0019] The crosslinked rubber composition X may also contain other rubber compounding agents such as a vulcanization accelerator aid, a processing aid, a vulcanization accelerator, and an antioxidant.

[0020] Examples of the vulcanization accelerator aid include metal oxides such as zinc oxide (zinc white) and magnesium oxide, metal carbonates, fatty acids and their derivatives, etc. The vulcanization accelerator aid preferably contains one or more of these, more preferably contains a metal oxide, even more preferably contains zinc oxide and / or magnesium oxide, and even more preferably contains both zinc oxide and magnesium oxide. Note that when the rubber component contains CR and the vulcanization accelerator aid contains a metal oxide, the metal oxide also acts as a crosslinking agent for the CR.

[0021] The content of the vulcanization accelerator aid in the crosslinked rubber composition X is preferably 5 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the rubber component.

[0022] 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. The content of the processing aid in the crosslinked rubber composition X is preferably 0.5 parts by mass or more and 1.5 parts by mass or less per 100 parts by mass of the rubber component.

[0023] Examples of the vulcanization accelerator 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, thiuram-based vulcanization accelerators, dithiocarbamate-based vulcanization accelerators, etc. The vulcanization accelerator preferably contains one or more of these, more preferably contains a sulfenamide-based vulcanization accelerator and / or a thiourea-based vulcanization accelerator, and even more preferably contains both a sulfenamide-based vulcanization accelerator and a thiourea-based vulcanization accelerator.

[0024] The content of the vulcanization accelerator in the crosslinked rubber composition X is preferably 2 parts by mass or more and 5 parts by mass or less per 100 parts by mass of the rubber component.

[0025] Examples of the antioxidant include p-phenylenediamine-based antioxidants, diphenylamine-based antioxidants, amine-ketone-based antioxidants, monophenol-based antioxidants, bisphenol-based antioxidants, polyphenol-based antioxidants, benzimidazole-based antioxidants, dithiocarbamate-based antioxidants, phosphorous-based antioxidants, organic thioacid-based antioxidants, etc. One or more of these antioxidants may be added.

[0026] The crosslinked rubber composition X is preferably crosslinked using sulfur as a crosslinking agent. In this case, the amount of sulfur blended into the uncrosslinked rubber composition X' is preferably 1 part by mass or more and 4 parts by mass or less per 100 parts by mass of the rubber component. The crosslinked rubber composition X may be crosslinked using an organic peroxide as a crosslinking agent.

[0027] In the wiper blade rubber 10 according to the embodiment, the viscoelastic properties of the crosslinked rubber composition X forming it are such that, where tanδ(-20°C) is the loss tangent at -20°C, tanδ(-25°C) is the loss tangent at -25°C, and tanδ(-30°C) is the loss tangent at -30°C, tanδ(-20°C)≦1.0, tanδ(-25°C)≧0.7, and tanδ(-30°C)≧0.6. From the viewpoint of suppressing curing in a low-temperature atmosphere, preferably tanδ(-20°C)≧0.7, more preferably tanδ(-20°C)≧0.8, and even more preferably tanδ(-20°C)≧0.9. From the same viewpoint, preferably 0.9≦tanδ(-25°C), more preferably 1.0≦tanδ(-25°C), preferably tanδ(-25°C)≦1.3, and more preferably tanδ(-25°C)≦1.1. From the same viewpoint, tan δ(-30°C) is preferably 0.7 or more, more preferably tan δ(-30°C) 0.8 or more, and preferably tan δ(-30°C) 1.0 or less. From the same viewpoint as above, the peak temperature of tan δ is preferably -22°C or more and -35°C or less, more preferably -24°C or more and -30°C or less. The viscoelastic properties of these crosslinked rubber compositions X are measured by a tensile method based on JIS K6394:2007.

[0028] Furthermore, the temperature t at which the specific modulus obtained from the Gehman torsion test of the crosslinked rubber composition X becomes 2 is ２ From the viewpoint of suppressing curing in a low-temperature atmosphere, the temperature is preferably −28° C. or lower, more preferably −30° C. or lower. ２ is determined based on JIS K6261-3:2017.

[0029] According to the wiper blade rubber 10 according to the above embodiment, the nitrogen adsorption specific surface area is 20 m ２ / g or more 40m ２The rubber composition is formed from a crosslinked rubber composition X having viscoelastic properties of tan δ(-20°C) ≦ 1.0, tan δ(-25°C) ≧ 0.7, and tan δ(-30°C) ≧ 0.6, and thus hardening in a low temperature atmosphere can be suppressed.

[0030] The wiper blade rubber 10 according to the embodiment can be produced by blending and kneading a rubber compounding agent containing carbon black A and a crosslinking agent with a rubber component to prepare an uncrosslinked rubber composition X', and then molding and crosslinking this uncrosslinked rubber composition X'. Examples of molding methods include press molding, extrusion molding, injection molding, and transfer molding.

[0031] (Crosslinked Rubber Composition) The crosslinked rubber compositions of Examples 1 to 4 and Comparative Examples 1 and 2 were each configured as follows: The composition of the uncrosslinked rubber composition before crosslinking is also shown in Table 1.

[0032] Example 1 NR (Mooney viscosity: 60 ml １＋４ (100°C)) and CR (mercaptan modified type, Mooney viscosity: 45-53ML １＋４ A blend rubber obtained by mixing NR and CR in a mass ratio of 60 / 40 (100°C) was used as the rubber component, and SRF (nitrogen adsorption specific surface area: 27 m) was used for 100 parts by mass of this rubber component. ２ An uncrosslinked rubber composition was prepared by blending and kneading 26 parts by mass of cellulose acetate copolymer (cellulose acetate copolymer, ...

[0033] Example 2 A crosslinked rubber composition was prepared in the same manner as in Example 1, except that a blend rubber prepared by mixing NR and CR in a mass ratio of NR / CR = 55 / 45 was used as the rubber component.

[0034] Example 3 A crosslinked rubber composition was prepared in the same manner as in Example 1, except that the amount of SRF mixed was 28 parts by mass per 100 parts by mass of the rubber component.

[0035] Example 4 A crosslinked rubber composition was prepared in the same manner as in Example 1, except that the compounding amount of SRF was 20 parts by mass per 100 parts by mass of the rubber component.

[0036] Comparative Example 1 A crosslinked rubber composition was prepared in the same manner as in Example 1, except that a blend rubber prepared by mixing NR and CR in a mass ratio of NR / CR = 50 / 50 was used as the rubber component.

[0037] Comparative Example 2 A crosslinked rubber composition was prepared as Comparative Example 2 in the same manner as in Example 1, except that the compounding amount of SRF was 30 parts by mass per 100 parts by mass of the rubber component.

[0038]

[0039] (Test and Evaluation Methods and Results) The following test and evaluation were carried out on each of the crosslinked rubber compositions of Examples 1 to 4 and Comparative Examples 1 and 2. The test results are shown in Table 2.

[0040] <Viscoelasticity Test> A viscoelasticity test was carried out by a tensile method based on JIS K6394:2007 for each of the crosslinked rubber compositions of Examples 1 to 4 and Comparative Examples 1 and 2, and tan δ (-20°C), tan δ (-25°C), tan δ (-30°C), and the peak temperature of tan δ were determined. The viscoelasticity test was carried out in a temperature variable mode with a frequency of 10 Hz, a dynamic strain of 0.1%, and a temperature increase of 2°C per minute in the temperature range from -60°C to 50°C.

[0041] <Gehman Torsion Test> A Gehman torsion test was carried out on each of the crosslinked rubber compositions of Examples 1 to 4 and Comparative Examples 1 and 2 in accordance with JIS K6261-3:2017. From the test results, the temperature t ２ asked for.

[0042] <Low-Temperature Sliding Property Test> Wiper blade rubbers having the same structure as that shown in FIG. 1 were produced using the crosslinked rubber compositions of Examples 1 to 4 and Comparative Examples 1 and 2.

[0043] The wiper blade rubbers formed from the crosslinked rubber compositions of Examples 1 to 4 and Comparative Examples 1 and 2 were subjected to a test in which they were slid across the surface of an automobile windshield in a low-temperature atmosphere of −15° C. Then, when almost no sliding noise was observed, the test was rated A, and when a clear sliding noise was observed, the test was rated B.

[0044]

[0045] The present invention is useful in the technical field of wiper blade rubber.

[0046] 10 wiper blade rubber 11 attachment holding portion 12 lip portion 13 neck portion 14 edge portion

Claims

1. A wiper blade rubber formed from a crosslinked rubber composition containing a rubber component and carbon black, wherein the nitrogen adsorption specific surface area of ​​the carbon black is 20 m ２ / g or more 40m ２ / g or less, an amount of the carbon black in the crosslinked rubber composition is 15 parts by mass or more and less than 30 parts by mass per 100 parts by mass of the rubber component, and when the loss tangent at -20°C is tanδ(-20°C), the loss tangent at -25°C is tanδ(-25°C), and the loss tangent at -30°C is tanδ(-30°C) in the viscoelastic properties of the crosslinked rubber composition, the following properties are satisfied: tanδ(-20°C)≦1.0, tanδ(-25°C)≧0.7, and tanδ(-30°C)≧0.

6.

2. The wiper blade rubber according to claim 1, wherein the rubber component is a blend rubber containing natural rubber and chloroprene rubber.

3. The wiper blade rubber according to claim 2, wherein the Mooney viscosity of the natural rubber is 50 ML. １＋４ (100℃) or more 80ML １＋４ (100°C) or less.

4. The wiper blade rubber according to claim 2 or 3, wherein the chloroprene rubber is a mercaptan-modified type.

5. The wiper blade rubber according to any one of claims 2 to 4, wherein the Mooney viscosity of the chloroprene rubber is 40 ML. １＋４ (100℃) or more 60ML １＋４ (100°C) or less.

6. The wiper blade rubber according to any one of claims 2 to 5, wherein the content of the natural rubber in the rubber component is greater than the content of the chloroprene rubber.

7. The wiper blade rubber according to claim 6, wherein the mass ratio (NR / CR) of the content of said natural rubber to the content of said chloroprene rubber in said rubber component is greater than 50 / 50 and not greater than 70 / 30.

8. A wiper blade rubber according to any one of claims 1 to 7, wherein the carbon black contains SRF.

9. The wiper blade rubber according to any one of claims 1 to 8, wherein the crosslinked rubber composition is crosslinked using sulfur as a crosslinking agent.

10. The wiper blade rubber according to any one of claims 1 to 9, wherein the temperature t at which the specific modulus obtained from the Gehman torsion test of the crosslinked rubber composition becomes 2 ２ A wiper blade rubber having a temperature of -28°C or lower.

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