JPS6366652B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing wiper blade rubber with low sliding resistance. Conventionally, as a manufacturing method for rubber sliding members with low sliding resistance, for example, a slippery fine powder (hereinafter referred to as "sliding material") made of graphite, molybdenum disulfide, and fluororesin powder is used in a roll mill or Banbury mixer. The crosslinking agent is mixed into an elastomer binder containing a crosslinking agent, and then formed into a sheet using a calender roll or the like, which is overlaid on the uncrosslinked product body, and then the elastomer binder and the product body are heated. There was a method in which a slippery layer was formed on the product body by integrally crosslinking it under pressure. However, in the case of this method, it is necessary to use a large amount of elastomer binder (usually 2.5 times or more in volume ratio) relative to the lubricating material due to processing constraints due to roll mills, banbury mixers, calender rolls, etc. The amount of lubricant inside was relatively small, and it actually had little effect on lowering the coefficient of friction. Moreover, when mixing the lubricant,
Formation of a slippery layer has not always been easy since the above-mentioned equipment must be used. Furthermore, with this method, it is difficult to uniformly form a slippery layer with a constant thickness on the surface of something with a thickness of about 0.6 to 1.0 mm, such as the lip of a wiper blade rubber, and the slippery layer becomes too thick. Cracks appeared on the lip, and there were also areas where the slippery layer was not formed. On the other hand, after forming the wiper blade rubber, it can be chlorinated to harden the surface to lower the sliding resistance, or a lubricant can be applied to the surface of the wiper blade rubber to reduce the sliding resistance. There are also methods to lower it. However, the former method does not have a sufficient effect of reducing sliding resistance, and the target wiper blade rubber is limited to diene rubber. Moreover, the latter has the drawback that it is not durable and the coating film peels off or wears out after short-term use. The present invention was created in view of the above-mentioned conventional problems, and improves wear resistance by forming a coating layer containing a lubricant on the surface of a molded material, and then performing pressure vulcanization molding. The present invention was based on the discovery that an excellent surface that is difficult to peel off can be obtained, and that by keeping the relative dimensions of the molding material and the split mold cavity within a certain range, a uniform coating layer can be formed on the surface of the lip of the wiper blade rubber. This is the completed version. That is, in the method for manufacturing wiper blade rubber of the present invention, a long molded material that is thin at the center and thick at both ends when viewed in cross section is formed into a material that is thin at the center when viewed in cross section and thick at both ends. is thin and forms the base of each wiper blade rubber, and is placed in a split mold with a long cavity that is thick at both ends when viewed in cross section, and the split mold is pressed in the closing direction to perform mold pressure vulcanization molding. Thereafter, the obtained molded body is 2
In a method of manufacturing two long wiper blade rubbers having a lip at one side end and a base at the other end by dividing, processing is performed on both surfaces of the central part of the molded material at least when viewed in cross section. in a sulfurized state
It has a coating layer containing the lubricant and a dispersion medium that disperses and holds the lubricant in an amount of 50% or more by volume, and the thickness at the center when viewed from the cross section of the molded material is the center when viewed from the cross section of the split cavity. 0.9 to 1.0 times the thickness of the part. One of the features of the manufacturing method of the present invention is that the thickness of the central portion of the molded material when viewed in cross section is 0.9 of the thickness of the central portion of the corresponding split cavity.
~1.0 times. In conventional mold pressure vulcanization molding, a rubber molded product with high dimensional accuracy is manufactured by using a molding material larger than the cavity volume. In the present invention, the thickness of the central part of the molded material that constitutes the lip of the wiper blade rubber is equal to or about 9/10 of the thickness of the corresponding cavity, contrary to the conventional method. and thin. As a result, the coating layer formed on the surface of the molding material and the base material are relatively stable, and a uniform coating layer is vulcanized and molded integrally with the base material on the surface of the resulting wiper blade rubber lip. . If the thickness of the center part of the molded material is thicker than the thickness of the corresponding cavity or, conversely, less than nine-tenths of the thickness of the corresponding cavity, the rubber in the center part of the molded material as seen in the cross section of the cavity will be thicker during pressure molding. The material flows violently, and as a result, the lip of the wiper blade rubber has a rough surface and the coating layer formed is uneven. In addition, when looking at the cross section of the molded material, the thicker parts at both ends are at an angle of 20 to 45 degrees with respect to the direction in which the thinner part in the center extends.
By forming a bonded shape at an angle in the range of 100°, it is possible to form a more stable and uniform coating layer on the surface of the resulting wiper blade rubber lip. This is because grooves extending in the longitudinal direction are formed at both ends of the molded material, and a large flow of material occurs during pressure molding, but when viewed in cross section, both ends and the center are formed within the above angle range. This is because by connecting them, the flow of material at both ends will not affect the center part as much. Note that the volume of the entire molding material should be slightly larger than the total volume of the cavity. The coating layer formed on both sides of at least the thin central portion of the molding material is composed of a lubricant that accounts for 50% or more by volume in a vulcanized state and a dispersion medium that retains the lubricant. If the content of the lubricant is less than 50% by volume, it is not possible to obtain the intended wiper blade rubber with low sliding resistance. To form this coating layer, a dispersion liquid is prepared by mixing and dispersing an uncrosslinked elastomer dispersion medium containing a lubricant and, if necessary, a crosslinking agent in a solvent, and this dispersion liquid is applied to the surface of the molding material. This is done by sprinkling off the solvent. As the lubricant, graphite, molybdenum disulfide, fluororesin fine powder, etc. with a particle size of 0.01 to 100 μm are used. The dispersion medium may be any elastomer that has adhesive properties with the base molding material, and is preferably made of the same material as the molding material. Other polymers such as PE and PP may be added to the elastomer. Also,
Similar to the molding material, compounding agents such as carbon black and zinc oxide may be added to the dispersion medium. As a crosslinking agent, sulfur or an organic peroxide capable of crosslinking the dispersion medium is appropriately added, and it is preferable to use the amount slightly larger than that added to a normal elastomer, since this increases the bonding strength of the dispersion medium. However, if the amount of crosslinking agent is too large, the dispersion medium will lose its flexibility, which is not preferable. Also, if the surface layer is extremely thin, the crosslinking agent in the molding material may migrate to the dispersion medium.
It is not necessarily necessary to add a crosslinking agent to the dispersion medium. As the solvent, toluene, xylene, trichloroethylene, trichloroethane, etc. can be used. The solvent is not particularly limited as long as it can uniformly disperse and maintain the dispersion medium, but a solvent that can dissolve the dispersion medium and is volatile is preferred. Note that the dispersion liquid is desirably adjusted to have a tortuosity suitable for coating as described below, depending on the dispersion medium content of the solvent. This dispersion liquid can be applied by dipping, brushing, or spraying to both surfaces of the central part, both surfaces of the central part and the surface of the part connected to the central part of the molding material, or the entire surface of the molding material when viewed in cross section. It is applied by methods such as The thickness of the coating layer is set to 5 to 30 μ after molding. The molding material may be any elastomer that can be crosslinked by heating, such as NR,
Synthetic rubbers such as SBR, CR, NBR, EPDM, etc., natural rubbers, or blends thereof may be mixed with a compounding agent containing a crosslinking agent as appropriate. EPDM can be used to obtain wiper blade rubber with high weather resistance. The process of placing the molding material on which the coating layer has been formed as described above in the cavity of a split mold and pressing the split mold to perform pressure vulcanization molding is the same as the conventional pressure vulcanization molding of wiper blade rubber. is the same as Examples will be explained below. First, 100 parts by weight of EPDM (hereinafter, parts mean parts by weight), 5 parts of bad lead oxide, 1 part of stearic acid,
An elastomer compound consisting of 40 parts of FEF carbon, 0.3 parts of powdered sulfur, and 6 parts of peroxide is thoroughly mixed using a Banbury mixer, and then an elongated molded material 2 having the cross-sectional shape shown in Fig. 1 is formed using an extrusion molding machine. adjusted. The maximum cross-sectional width a of this molded material is approximately 24 mm, the width b of the thin parallel portion 1 at the center of the cross section is 4 mm, and the angle (α) between the direction in which this parallel portion 1 extends and the connecting portion 3 of the thick portions 2 at both ends is It was set to 25 degrees. Also, the thickness c of the parallel part 1 is
It was set to 0.65mm. Note that the thickness c of the parallel portion 1 corresponds to 0.93 times the thickness d of the central portion of the cavity 7 of the split molds 5 and 6, which will be described later. Next, it is used as a dispersion medium as a coating layer forming material.
A rubber material containing 100 parts of EPDM, 0.3 parts of powdered sulfur, and 6 parts of peroxide was used, a lubricant was used in the proportions shown in the table, and trichlorethylene was used as a solvent, and the mixture was thoroughly mixed to form No. 1 to No. 6 of 6
Various dispersions were prepared. These six types of dispersion liquids were each applied to the surface of the above-mentioned molding material by brush coating, and then sufficiently dried to form a coating layer 4 as shown in FIG. 3. The mold used was a split mold consisting of an upper mold 5 and a lower mold 6, the cross section of which is shown in FIG. This split-type cavity 7 is formed by integrally pressurizing and vulcanizing two wiper blade rubbers, and has a configuration in which the lip tips of the two wiper blade rubbers are connected. This cavity 7
is the central thin part 7 when viewed in cross section forming the lip.
1, base portions 72 at both ends, and a connecting portion 73 having a substantially triangular cross section connecting them. When viewed in cross section of the cavity 7, the thickness d of the central thin portion 71 is 0.7 mm. This mold is heated to 175°C, and as shown in Fig. 3, the molding material with the coating layer 4 formed on its surface is placed on the mold surface of the lower mold 6, and the upper mold 5 is placed on top of it using a hydraulic press. It was pressed and molded by pressure vulcanization. After molding, it was divided into two parts in the length direction, and six types of wiper blade rubbers 8, the cross sections of which are shown in FIG. 4, were manufactured. This wiper blade rubber 8 has a lip 81 and

【table】

[Table] It consists of a trunk 82 at the other end of the lip 81 and a connecting part 83 with a substantially triangular cross section located in the middle thereof.
Note that the lip 81 and the connecting portion 83 also come into contact with the glass surface, so they can be referred to as sliding members. On both sides of the lip 81 and the connecting part 83,
A coating layer 84 having a uniform thickness of 10μ to 15μ was formed. In order to see the sliding resistance of these wiper blade rubbers, each wiper blade rubber was clamped as shown in Figure 5, and while applying a force of W = 20gf/cm x 10cm, muddy water was intermittently poured onto the glass. It was slid back and forth on the surface at a distance of 50 cm at a speed of 35 times/min, and μ (initial friction coefficient) = F (tensile load) / W (load) was measured for the initial few times. The measurement results are shown in the table. For comparison, a wiper blade rubber was manufactured using only a base material on which no coating layer was formed, and the initial coefficient of friction was similarly measured. The results are also shown in the table. From the table, it can be seen that the wiper blade rubber of the present invention has a small initial friction coefficient of 2.1 or less and low sliding resistance. Especially when the lubricant/dispersion medium is 2.0 or more,
It can be seen that extremely excellent results have been obtained with an initial friction coefficient of 1.0 or less. Further, as a durability test, the above sliding test was repeated, and the degree of increase in the coefficient of friction after sliding back and forth a predetermined number of times was measured with the initial value = 1. As shown in the experiment shown in FIG. 6, the wiper blade rubber of Example 4 had a substantially constant friction coefficient, and it was confirmed that it could maintain low sliding resistance even during long-term use. As mentioned above, the wiper blade rubber obtained by the manufacturing method of the present invention contains 50% by volume of slippery fine powder.
Since the coating layer contained above is molded by pressure vulcanization, it has a low coefficient of friction and low sliding resistance (see table), and is also excellent in durability (see Fig. 6).

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a molding material for wiper blade rubber used in an example of the present invention, FIG. 2 is a cross-sectional view of a mold for molding the wiper blade rubber of the example, and FIG. A cross-sectional view showing a state in which a coating layer is formed on the molding material shown in Figure 2 and placed on the lower die of the mold shown in Figure 2, Figure 4 is a cross-sectional view of the wiper blade rubber obtained in the example, and Figure 5. 6 is a model diagram showing a method of measuring the coefficient of friction, and FIG. 6 is a diagram showing the durability of the wiper blade rubber of this example. In the figure, 1 is the center part as seen in the cross section of the molding material, 2 is the both ends as seen in the cross section of the molding material, 3 is the connecting part, 4 is the covering layer, 5 is the upper mold, 6 is the lower mold, and 7 is the cavity. , 8 indicates wiper blade rubber.

Claims (1)

[Scope of Claims] 1. A long molded material that is thin at the center and thick at both ends when viewed in cross section, and formed into two wiper blade rubbers that are thin at the center and thick at both ends when viewed in cross section. Placed in a split mold having an elongated cavity with thick ends when viewed in cross section forming the base of the mold, press the split mold in the closing direction to perform mold pressure vulcanization molding, and then the molded molded product obtained. In a method of manufacturing two long wiper blade rubbers having a lip at one end and a base at the other end by dividing the body into two in the length direction, the above-mentioned molded material is at least in the center when viewed in cross section. On both sides of the molded material, there is a coating layer containing 50% by volume or more of a lubricant in a vulcanized state and a dispersion medium that disperses and holds the lubricant, and the central part of the molded material is The thickness is the thickness of the central part of the cavity, which forms the lip of the wiper blade rubber, when viewed in cross section.
A method for producing wiper blade rubber, characterized in that it is 0.9 to 1.0 times. 2. The manufacturing method according to claim 1, wherein the molded material has a shape in which both end portions are joined at an angle in the range of 20 degrees to 45 degrees with respect to the direction in which the central portion extends when viewed in cross section.