Surface treatment agent for vulcanized rubber, method for manufacturing bonded structure, bonded structure, and tire

Abstract

Provided is a vulcanized rubber surface processing agent which enables vulcanized rubber pieces to be securely adhered to each other without heating, and with which rubber degradation effects are small. This vulcanized rubber surface processing agent is characterized by being used for adhering vulcanized rubber pieces to each other, and by being a hypochlorous acid aqueous solution with a pH of 2-7 and with an effective chlorine concentration of 100-13000ppm.

Description

[Technical Field]

[0001] The present invention relates to a surface treatment agent for vulcanized rubber, a method for producing a bonded structure, a bonded structure, and a tire. [Background technology]

[0002] In recent years, from the perspective of resource conservation and initial cost reduction, an approach has been promoted for various types of tires to reuse them by repairing or partially replacing parts that have deteriorated through use.Specific examples include retreading, which replaces worn treads, restiding parts of sidewalls damaged by sidewalk curbs, and repairing cracks that have appeared on the tire surface.

[0003] In the technology for repairing and reusing tires as described above, adhesion between vulcanized rubber components and other components, particularly adhesion between vulcanized rubber components, is often required. In such cases, high adhesion between the components is naturally required. It is also important that the repaired portion of the tire has high fatigue resistance (ability to withstand tire deformation) when reused. Furthermore, convenience during repair and other work is also important.

[0004] In this regard, for example, Patent Document 1 discloses that strong and stable adhesion can be achieved by sequentially applying (1) a primer mainly composed of halogenated polyolefin, (2) a rubber-based adhesive mainly composed of halogenated rubber, and (3) a urethane-based adhesive to a rubber surface, and then sandwiching the surface between other members. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 1-131291 Summary of the Invention [Problem to be solved by the invention]

[0006] The technology of Patent Document 1 achieves adhesiveness by heat and pressure bonding. Therefore, in the case of large tires in particular, it is difficult to perform work while the tire is still attached. Furthermore, given that tire repairs are often performed on-site, it is desirable to be able to firmly bond vulcanized rubber components together without the need for heating.

[0007] Furthermore, in the prior art of Patent Document 1, an organic solvent is applied to the rubber surface, which may cause deterioration of the rubber.

[0008] In light of the above, there is a need to develop a treatment agent that will provide the desired specific activity when applied to the surface of vulcanized rubber.

[0009] Therefore, an object of the present invention is to provide a vulcanized rubber surface treatment agent that enables vulcanized rubbers to be firmly bonded to each other without the need for heating and that has little effect on rubber degradation. Another object of the present invention is to provide a method for producing a bonded structure, which is capable of producing a bonded structure in which vulcanized rubbers are firmly bonded to each other without requiring heating. Another object of the present invention is to provide an adhesive structure in which vulcanized rubbers are firmly bonded to each other and have excellent fatigue resistance, and a tire including the adhesive structure. [Means for solving the problem]

[0010] The gist and configuration of the present invention to solve the above problems is as follows.

[0011] The vulcanized rubber surface treatment agent of the present invention is a vulcanized rubber surface treatment agent used for bonding vulcanized rubbers together, and is It is characterized by being an aqueous hypochlorous acid solution having a pH value of 2 or more and 7 or less, and an effective chlorine concentration of 100 ppm or more and 13,000 ppm or less.

[0012] Further, the method for producing a bonded structure of the present invention is a method for producing a bonded structure in which a first vulcanized rubber and a second vulcanized rubber are bonded together, the method comprising the steps of: a first application step of applying an aqueous hypochlorous acid solution having a pH value of 2 or more and 7 or less and an effective chlorine concentration of 100 ppm or more and 13,000 ppm or less to a surface of the first vulcanized rubber; A second application step of applying an adhesive to the surface of the hypochlorous acid aqueous solution applied in the first application step; a bonding step of bonding the first vulcanized rubber and the second vulcanized rubber together via the hypochlorous acid aqueous solution applied in the first application step and the adhesive applied in the second application step; The present invention is characterized in that it includes:

[0013] The bonded structure of the present invention is a bonded structure in which a first vulcanized rubber and a second vulcanized rubber are bonded via an adhesive layer, the adhesive layer contains a urethane compound and / or an epoxy compound, The first vulcanized rubber and the second vulcanized rubber are characterized in that at least a portion of the surface that comes into contact with the adhesive layer is chlorinated.

[0014] The tire of the present invention is characterized by including the above-mentioned adhesive structure. [Effects of the Invention]

[0015] According to the present invention, it is possible to provide a vulcanized rubber surface treatment agent that enables vulcanized rubbers to be firmly bonded to each other without the need for heating and that is less susceptible to rubber degradation. Furthermore, according to the present invention, it is possible to provide a method for producing a bonded structure, which is capable of producing a bonded structure in which vulcanized rubbers are firmly bonded to each other without requiring heating. Furthermore, according to the present invention, it is possible to provide an adhesive structure in which vulcanized rubbers are firmly bonded to each other and which has excellent fatigue resistance, and a tire including the adhesive structure. DETAILED DESCRIPTION OF THE INVENTION

[0016] The present invention will be described in detail below based on embodiments.

[0017] (surface treatment agent for vulcanized rubber) A vulcanized rubber surface treatment agent according to one embodiment of the present invention (hereinafter sometimes referred to as "the surface treatment agent of this embodiment") is used for bonding vulcanized rubbers together. The surface treatment agent of this embodiment is characterized in that it is an aqueous hypochlorous acid solution having a pH value of 2 or more and 7 or less, and an effective chlorine concentration of 100 ppm or more and 13,000 ppm or less.

[0018] In addition, in an aqueous hypochlorous acid solution having a pH value of 2 or more and 7 or less, hypochlorous acid exists mostly in the form of molecules (HClO).

[0019] The present inventors have conducted extensive research into methods for improving adhesion between vulcanized rubbers. As a result, they have discovered that high adhesion can be achieved without the need for heating by surface treating at least one of the vulcanized rubbers with a hypochlorous acid aqueous solution prior to bonding the vulcanized rubbers together using an adhesive. It is known that hypochlorous acid aqueous solutions are typically used for sterilization, deodorization, and the like. Therefore, the fact that the use of a hypochlorous acid aqueous solution as a surface treatment agent for vulcanized rubbers improves the adhesion between vulcanized rubbers is a novel and surprising discovery.

[0020] Furthermore, since the surface treatment agent of this embodiment is an aqueous solution (containing no organic solvents), it has little adverse effect on the environment and also has a sufficiently small effect on the degradation of vulcanized rubber with which it comes into direct contact. Therefore, an adhesive structure obtained by applying the surface treatment agent of this embodiment to the surface of vulcanized rubber and sandwiching an adhesive therebetween not only has high adhesion, but can also significantly withstand deformation and strain (has high fatigue resistance).

[0021] Furthermore, the aqueous solution of hypochlorous acid has the advantage that it can be easily prepared using commercially available raw materials.

[0022] It is believed that when a hypochlorous acid solution is applied to the surface of vulcanized rubber, an oxidation (chlorination) reaction of the olefin moiety occurs on at least a portion of the vulcanized rubber surface. In this oxidation (chlorination) reaction, chlorine and hydroxyl groups are introduced to the carbon atoms that previously formed C=C double bonds in the rubber molecules present on the vulcanized rubber surface, via the mechanism shown below. The introduction of these groups is believed to increase the polarity of the vulcanized rubber surface, improving its wettability and contributing to strong adhesion. Therefore, a certain amount of hypochlorous acid present in the molecular (HClO) state in the aqueous solution is necessary; the presence of hypochlorous acid in the ionic state alone is insufficient to sufficiently increase the polarity of the vulcanized rubber surface. Furthermore, whether hypochlorous acid exists in the molecular or ionic state in the aqueous solution can be determined by the pH value of the solution. A pH value of 7 or below is believed to provide sufficient hypochlorous acid molecules to increase the polarity of the vulcanized rubber surface.

[0023] [ka]

[0024] The hypochlorous acid aqueous solution as the surface treatment agent of this embodiment can be used, for example, in the manufacturing method of a bonded structure described below.

[0025] As described above, the pH value of the hypochlorous acid aqueous solution used as the surface treatment agent of this embodiment is 2 or more and 7 or less. If the pH value is less than 2, a large amount of chlorine gas is released, making it difficult to maintain the effective chlorine concentration within a predetermined range. If the pH value is more than 7, the effect of improving the adhesion between vulcanized rubbers cannot be sufficiently obtained. From the viewpoint of stability, the pH value of the hypochlorous acid aqueous solution is more preferably 4 or more.

[0026] In addition, as described above, the effective chlorine concentration of the hypochlorous acid aqueous solution as the surface treatment agent of this embodiment is 100 ppm or more and 13,000 ppm or less. If the effective chlorine concentration is less than 100 ppm, the adhesiveness between vulcanized rubbers cannot be sufficiently improved. If the effective chlorine concentration is more than 13,000 ppm, the adhesiveness between vulcanized rubbers deteriorates and there is a risk to human health. From the same viewpoint, the effective chlorine concentration of the hypochlorous acid aqueous solution is preferably 200 ppm or more, more preferably 300 ppm or more, and preferably 8,000 ppm or less, more preferably 4,000 ppm or less, even more preferably 1,000 ppm or less, and even more preferably 500 ppm or less.

[0027] The effective chlorine concentration of the hypochlorous acid aqueous solution can be adjusted, for example, by the dilution ratio when dissolving a hypochlorite such as sodium hypochlorite in water to obtain an aqueous solution. The pH value of hypochlorous acid aqueous solution can be reduced by adding hydrochloric acid to the hypochlorous acid aqueous solution, and can be adjusted by adjusting the ratio of adding hydrochloric acid.The pH value of the aqueous solution obtained by dissolving sodium hypochlorite in water is about 9 to 10.In addition, if a large amount of chlorine is added to the hypochlorous acid aqueous solution or if it is added suddenly, chlorine gas will be generated, and the effective chlorine concentration will decrease accordingly, so care should be taken when adjusting.

[0028] (Method of manufacturing bonded structure) A method for producing a bonded structure according to one embodiment of the present invention (hereinafter sometimes referred to as "the production method of this embodiment") is a method for producing a bonded structure in which a first vulcanized rubber and a second vulcanized rubber are bonded together. Specifically, the production method of this embodiment includes the following steps: a first application step of applying an aqueous hypochlorous acid solution having a pH value of 2 or more and 7 or less and an effective chlorine concentration of 100 ppm or more and 13,000 ppm or less to a surface of the first vulcanized rubber; A second application step of applying an adhesive to the surface of the hypochlorous acid aqueous solution applied in the first application step; a bonding step of bonding the first vulcanized rubber and the second vulcanized rubber together via the hypochlorous acid aqueous solution applied in the first application step and the adhesive applied in the second application step; According to the manufacturing method of this embodiment, it is possible to manufacture a bonded structure in which vulcanized rubbers are firmly bonded to each other without the need for heating. Furthermore, the bonded structure manufactured by the manufacturing method of this embodiment can significantly withstand deformation and strain (has high fatigue resistance).

[0029] The vulcanized rubbers (first vulcanized rubber and second vulcanized rubber) can be prepared by vulcanizing a rubber composition containing a rubber component. Examples of the rubber component include diene-based rubber components such as natural rubber, butadiene rubber, styrene-butadiene rubber, isoprene rubber, chloroprene rubber, ethylene-propylene-diene copolymer, and acrylonitrile-butadiene rubber. The rubber component may be a single component or a combination of two or more components. Furthermore, the vulcanized rubbers and the rubber compositions used to prepare the vulcanized rubbers may contain appropriate amounts of additives, such as fillers such as carbon black, vulcanizing agents such as sulfur, vulcanization accelerators, vulcanization accelerator assistants, zinc oxide, antioxidants, antioxidants, foaming agents, plasticizers, lubricants, tackifiers, and ultraviolet absorbers, depending on the purpose. The vulcanization conditions are not particularly limited. Furthermore, the vulcanized rubber may include a member other than rubber, such as a fiber member or a metal member, depending on the purpose.

[0030] Examples of the antioxidant include aromatic secondary amine-based antioxidants, phenol-based antioxidants, sulfur-based antioxidants, and phosphite-based antioxidants.

[0031] Examples of aromatic secondary amine antioxidants include N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (6PPD), N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD), N,N'-diphenyl-p-phenylenediamine (DPPD), N,N'-di-2-naphthyl-p-phenylenediamine (DNPD), N-(3-methacryloyloxy-2-hydroxypropyl)-N'-phenyl-p-phenylenediamine, and N-cyclohexyl Examples of antioxidants include p-phenylenediamine antioxidants such as sil-N'-phenyl-p-phenylenediamine; diphenylamine antioxidants such as p-(p-toluenesulfonylamido)diphenylamine, 4,4'-bis(α,α-dimethylbenzyl)diphenylamine (CD), octylated diphenylamine (ODPA), and styrenated diphenylamine; and naphthylamine antioxidants such as N-phenyl-1-naphthylamine (PAN) and N-phenyl-2-naphthylamine (PBN).

[0032] Furthermore, as the aromatic secondary amine-based antioxidant, a p-phenylenediamine-based antioxidant is preferred, and the p-phenylenediamine-based antioxidant is preferably one having a structure that does not have a double bond other than the phenylenediamine moiety, and further preferably one having a structure represented by the following general formula (1): [ka] [In the formula, R 1 and R 2 R is each independently a monovalent saturated hydrocarbon group. 1 and R 2 may be the same or different, but from the viewpoint of synthesis, they are preferably the same.

[0033] The number of carbon atoms in the monovalent saturated hydrocarbon group is preferably 1 to 20, more preferably 3 to 10, and particularly preferably 6 or 7. When the number of carbon atoms in the saturated hydrocarbon group is 20 or less, the number of moles per unit mass increases, resulting in a greater anti-aging effect and improved ozone resistance of the vulcanized rubber and / or rubber composition. R in the above general formula (1) 1 and R 2 and are preferably each independently a linear or cyclic monovalent saturated hydrocarbon group having 1 to 20 carbon atoms, from the viewpoint of further improving the ozone resistance of the vulcanized rubber and / or rubber composition.

[0034] Examples of the monovalent saturated hydrocarbon group include an alkyl group and a cycloalkyl group. The alkyl group may be linear or branched, and the cycloalkyl group may further have an alkyl group or the like bonded thereto as a substituent. Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a 1,2-dimethylbutyl group, a 1,3-dimethylbutyl group, a 2,3-dimethylbutyl group, an n-pentyl group, an isopentyl group, a neopentyl group, a 1-methylpentyl group, a 2-methylpentyl group, a 3-methylpentyl group, a 4-methylpentyl group, a 1,2-dimethylpentyl group, a 1,3-dimethylpentyl group, a 1,4-dimethylpentyl group, a 2,3-dimethylpentyl group, a 2,4-dimethylpentyl group, a 3,4-dimethylpentyl group, an n-hexyl group, a 1-methylhexyl group, a 2-methylhexyl group, various octyl groups, various decyl groups, and various dodecyl groups. Of these, a 1,4-dimethylpentyl group is preferred. Examples of the cycloalkyl group include a cyclopentyl group, a methylcyclopentyl group, a cyclohexyl group, a methylcyclohexyl group, a cycloheptyl group, and a cyclooctyl group. Of these, a cyclohexyl group is preferred.

[0035] The p-phenylenediamine compound represented by the general formula (1) may be supported on any carrier, for example, the p-phenylenediamine compound represented by the general formula (1) may be supported on an inorganic filler such as silica or calcium carbonate. The p-phenylenediamine compound represented by the general formula (1) may also constitute a masterbatch together with the rubber component used in the vulcanized rubber. The p-phenylenediamine compound represented by the general formula (1) may be converted into a salt with an organic acid. The organic acid used to convert the salt is not particularly limited, but examples thereof include stearic acid.

[0036] The first vulcanized rubber and the second vulcanized rubber preferably have a concentration of the aromatic secondary amine antioxidant of 1% by mass or less. Because aromatic secondary amine antioxidants can have unintended effects on the adhesion between vulcanized rubbers, keeping the concentration at 1% by mass or less can maintain sufficiently high adhesion between vulcanized rubbers. Here, the concentration of each component in the vulcanized rubber can usually be calculated from the component composition (compounding ratio) of the rubber composition used to prepare the vulcanized rubber.

[0037] However, since adhesion is performed on the surface of the vulcanized rubber, the above concentration is sufficient as long as it is satisfied at least in the surface layer of the vulcanized rubber. Specifically, it is preferable that the first vulcanized rubber and the second vulcanized rubber have a concentration of the aromatic secondary amine antioxidant of 1 mass % or less in a region 10 μm deep from the surface that will come into contact with the adhesive (in the subsequent adhesion step). The concentration in a region 10 μm deep from the surface of the vulcanized rubber can be measured, for example, by gas chromatography of a wiped sample from the surface.

[0038] Regarding the above, the concentration of the aromatic secondary amine antioxidant in the surface layer of the vulcanized rubber can be reduced, for example, by treating the surface of the vulcanized rubber with an organic solvent such as acetone (for example, by impregnating a rag with the solvent and wiping it off).

[0039] Furthermore, from the same viewpoint, the concentration of the aromatic secondary amine antioxidant in the first vulcanized rubber and the second vulcanized rubber (or the surface layer thereof) is more preferably 0.6% by mass or less, further preferably 0.3% by mass or less, and may even be 0% by mass.

[0040] The first vulcanized rubber and the second vulcanized rubber may be independent vulcanized rubber components, or may be located at any two positions in the same vulcanized rubber component. Furthermore, the first vulcanized rubber and the second vulcanized rubber may be the same or different in rubber type, component shape, and content of various additives.

[0041] In the first application step, an aqueous solution of hypochlorous acid having a pH value of 2 or more and 7 or less and an effective chlorine concentration of 100 ppm or more and 13,000 ppm or less is applied to the surface of the first vulcanized rubber. In this step, the bonding surface of the vulcanized rubber is treated with an aqueous solution (organic solvent-free), so rubber deterioration is sufficiently suppressed. The amount of application is not particularly limited, and it is sufficient to apply enough so that the surface to be bonded is covered. The application method is also not particularly limited.

[0042] The aqueous hypochlorous acid solution used in the first application step preferably has a pH value of 4 or more and 7 or less from the viewpoint of stability.

[0043] In the manufacturing method of this embodiment, it is preferable to apply an aqueous hypochlorous acid solution to the surface of the second vulcanized rubber as in the case of the first vulcanized rubber.

[0044] Next, in the second application step, an adhesive is applied to the surface of the hypochlorous acid aqueous solution applied in the first application step. The amount of application is not particularly limited, and it is sufficient to apply the adhesive so that the hypochlorous acid aqueous solution on the surface of the first vulcanized rubber is covered. The application method is not particularly limited.

[0045] The adhesive is not particularly limited and can be appropriately selected depending on the purpose. The adhesive may be used alone or in combination of two or more. In particular, it is preferable to use an adhesive that can exhibit adhesiveness at room temperature, and from the viewpoint of exhibiting sufficiently high adhesiveness, it is preferable to use a urethane adhesive and / or an epoxy adhesive. In this case, the vulcanized rubbers can be bonded together more firmly.

[0046] Next, in the bonding step, the first vulcanized rubber and the second vulcanized rubber are bonded together via the hypochlorous acid aqueous solution applied in the first coating step and the adhesive applied in the second coating step. This allows for a bonded structure in which the two vulcanized rubbers are firmly bonded together. More specifically, in the bonding step, the first vulcanized rubber and the second vulcanized rubber are bonded together by bonding them together via the coating and applying appropriate pressure. Here, if both the first vulcanized rubber and the second vulcanized rubber have been coated as described above, they can be bonded together with the coated surfaces of the two vulcanized rubbers facing each other.

[0047] After laminating the first vulcanized rubber and the second vulcanized rubber, it is preferable to dry them to remove the water content in the hypochlorous acid aqueous solution. In this case, the drying temperature may be room temperature. The drying time may be, for example, about 2 to 7 days.

[0048] Through the above-described steps, a bonded structure in which the first vulcanized rubber and the second vulcanized rubber are bonded together can be obtained.

[0049] In the manufacturing method of this embodiment, a polishing step may be carried out in advance to polish the bonding surfaces of the first vulcanized rubber and the second vulcanized rubber with a grindstone or the like. In this case, the adhesiveness can be further improved by the anchor effect.

[0050] In addition, the manufacturing method of this embodiment may include a step of treating the surfaces of the first vulcanized rubber and the second vulcanized rubber that come into contact with each other with an organic solvent such as acetone to reduce the concentration of a predetermined component (e.g., an aromatic secondary amine antioxidant) in the surface layer. This step is particularly useful when the concentration of the aromatic secondary amine antioxidant in the rubber composition used to prepare the vulcanized rubber is relatively high.

[0051] (Adhesive structure) An adhesive structure according to one embodiment of the present invention (hereinafter, sometimes referred to as "adhesive structure of this embodiment") is an adhesive structure in which a first vulcanized rubber and a second vulcanized rubber are adhered via an adhesive layer, the adhesive layer contains a urethane compound and / or an epoxy compound, The first vulcanized rubber and the second vulcanized rubber are characterized in that at least a portion of the surface thereof that comes into contact with the adhesive layer is chlorinated. In the bonded structure of this embodiment, the vulcanized rubbers are firmly bonded to each other and have excellent fatigue resistance.

[0052] The bonded structure of this embodiment can be preferably produced by the manufacturing method of this embodiment described above. In addition, the bonded structure of this embodiment can be preferably produced by using the surface treatment agent of this embodiment described above.

[0053] Specific examples of the first vulcanized rubber and the second vulcanized rubber are the same as those already described.

[0054] Furthermore, from the same viewpoint as that already described for the manufacturing method of this embodiment, it is preferable that the first vulcanized rubber and the second vulcanized rubber have a concentration of the aromatic secondary amine-based antioxidant of 1 mass % or less in a region 10 μm deep from the surface in contact with the adhesive layer.

[0055] The urethane compound and / or epoxy compound contained in the adhesive layer can be derived from a urethane-based adhesive and / or an epoxy-based adhesive as the adhesive.

[0056] The phrase "the surface of the vulcanized rubber is chlorinated" essentially means that the rubber molecules present on the surface of the vulcanized rubber have chlorine groups.

[0057] In addition, in the bonded structure of this embodiment, the chlorine group is preferably bonded to a carbon atom constituting a rubber molecule present on the surface of the vulcanized rubber. Furthermore, it is preferable that the rubber molecules present on the surfaces of the first vulcanized rubber and the second vulcanized rubber that come into contact with the adhesive layer have hydroxyl groups, and it is more preferable that the hydroxyl groups are bonded to carbon atoms that constitute the rubber molecules present on the surface of the vulcanized rubber. All of the above-mentioned aspects can be achieved, for example, by applying an aqueous solution of hypochlorous acid to a predetermined surface of vulcanized rubber.

[0058] (tire) A tire according to one embodiment of the present invention is characterized by including the adhesive structure according to the present embodiment described above. The tire according to the present embodiment has excellent fatigue resistance because it uses the adhesive structure. Note that the location of the adhesive structure in the tire is not particularly limited and can be appropriately selected depending on the purpose. [Example]

[0059] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples in any way.

[0060] (Production of vulcanized rubber) Unvulcanized rubber compositions were prepared by thoroughly kneading the ingredients according to the formulations shown in Tables 1 and 2. These rubber compositions were vulcanized and molded into predetermined sheets at 165°C for 10 minutes to produce a pair of vulcanized rubber sheets (first and second vulcanized rubber sheets). The first and second vulcanized rubber sheets used in each example were essentially identical to each other, and for convenience they will be referred to as "first" and "second," respectively.

[0061] (Preparation of surface treatment agent) A hypochlorous acid aqueous solution (surface treatment agent) was prepared by dissolving sodium hypochlorite (manufactured by Tokyo Chemical Industry Co., Ltd.) in water and adding hydrochloric acid (manufactured by Tokyo Chemical Industry Co., Ltd.) as needed to achieve the effective chlorine concentration and pH shown in Tables 1 and 2. In Comparative Example 1, a 4% ethyl acetate solution of trichloroisocyanuric acid (manufactured by LORD) was prepared as the surface treatment agent instead of the hypochlorous acid aqueous solution. The available chlorine concentration was measured using a residual chlorine measuring instrument manufactured by Kyowa Pure Chemical Industries, Ltd., and the pH was measured using "Camelmo" manufactured by Toa DKK Corporation.

[0062] (Fabrication of adhesive structures) The first vulcanized rubber sheet and the second vulcanized rubber sheet were immersed in the surface treatment agent for 1 minute to perform a surface treatment. After immersion, excess liquid adhering to the surface of the first vulcanized rubber sheet was wiped off, and then, using 100 μm-thick masking tape as a spacer, the adhesive shown in Tables 1 and 2 was applied to the surface of the first vulcanized rubber sheet (application thickness: 100 μm). Next, the coated surface of the first vulcanized rubber sheet was placed facing up, and the second vulcanized rubber sheet was placed on top of it. Furthermore, a weight was placed on top to apply pressure, and the sheet was left at room temperature for 4 days. In this way, an adhesive structure was produced in which the adhesive was sandwiched between the first vulcanized rubber sheet and the second vulcanized rubber sheet. In measuring the peel strength described below, first and second vulcanized rubber sheets each having a length of 60 mm, a width of 30 mm and a thickness of 5 mm were used to prepare bonded structures as described above. In addition, when evaluating the fatigue resistance described below, first and second vulcanized rubber sheets measuring 50 mm in length, 10 mm in width, and 5 mm in thickness were used, and the two sheets were offset from each other by 10 mm in the longitudinal direction to form a handle portion, and an adhesive structure was prepared as described above.

[0063] (Peel force measurement) The bonded structures prepared in each example were subjected to a T-peel test at a tensile speed of 500 mm / min using a universal testing machine manufactured by Instron Corp., and the peel strength (N / 25 mm) was measured. The results are shown in Tables 1 and 2. In addition, if the peel strength is 150 N / 25 mm or more, particularly 220 N / 25 mm or more, the adhesiveness can be considered to be good.

[0064] (Evaluation of fatigue resistance) The handle portion of the bonded structure produced in each example was chucked, and a 50% strain was applied in the longitudinal direction under conditions of a frequency of 6 Hz and an ambient temperature of 60°C. The number of strain inputs required to propagate a 1 mm crack was then measured. The number of inputs for each example was indexed, with the number of inputs for Comparative Example 1 set to 100. The results are shown in Tables 1 and 2. A higher index value indicates better fatigue resistance. In addition, for examples in which the measured peel force was less than 150 N / 25 mm, the samples peeled off easily, and therefore fatigue resistance could not be evaluated.

[0065] [Table 1]

[0066] [Table 2]

[0067] *1 Carbon black: LS-HAF Iodine adsorption capacity 87mg / g DBP 74ml / 100g *2 Vulcanization accelerator: "Noccela CZ-G" manufactured by Ouchi Shinko Chemical Industry Co., Ltd. *3 Antioxidant: N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (aromatic secondary amine antioxidant) *4 Urethane adhesive: Cemedine, "UM880" *5 Epoxy adhesive: LORD "Fusor" *6 Instead of the hypochlorous acid solution, a 4% solution of trichloroisocyanuric acid in ethyl acetate (manufactured by LORD) was used.

[0068] Tables 1 and 2 show that in the examples in which an aqueous hypochlorous acid solution with a pH value of 2 or more and 7 or less and an effective chlorine concentration of 100 ppm or more and 13,000 ppm or less was used as a vulcanized rubber surface treatment agent, the vulcanized rubbers were firmly bonded together via the adhesive while exhibiting high fatigue resistance compared to the comparative examples.

[0069] Furthermore, a comparison of Examples 4, 6 and 7 shows that the lower the concentration of the predetermined antioxidant in the first vulcanizate and the second vulcanizate, the better both the peel force and fatigue resistance become. [Industrial Applicability]

[0070] According to the present invention, it is possible to provide a vulcanized rubber surface treatment agent that enables vulcanized rubbers to be firmly bonded to each other without the need for heating and that is less susceptible to rubber degradation. Furthermore, according to the present invention, it is possible to provide a method for producing a bonded structure, which is capable of producing a bonded structure in which vulcanized rubbers are firmly bonded to each other without requiring heating. Furthermore, according to the present invention, it is possible to provide an adhesive structure in which vulcanized rubbers are firmly bonded to each other and which has excellent fatigue resistance, and a tire including the adhesive structure.

Claims

1. A method for producing a bonded structure for obtaining a bonded structure in which a first vulcanized rubber and a second vulcanized rubber are bonded, comprising the steps of: a first application step of applying an aqueous hypochlorous acid solution having a pH value of 2 or more and 7 or less and an effective chlorine concentration of 100 ppm or more and 13,000 ppm or less to a surface of the first vulcanized rubber; A second application step of applying an adhesive to the surface of the hypochlorous acid aqueous solution applied in the first application step; an adhering step of adhering the first vulcanized rubber and the second vulcanized rubber via the hypochlorous acid aqueous solution applied in the first application step and the adhesive applied in the second application step; A method for producing a bonded structure, comprising:

2. 2. The method for producing an adhesive structure according to claim 1, wherein the first vulcanized rubber and the second vulcanized rubber have a concentration of an aromatic secondary amine-based antioxidant of 1 mass % or less in a region 10 μm deep from the surface in contact with the adhesive.

3. The method for producing a bonded structure according to claim 1 or 2, wherein the adhesive is a urethane adhesive and / or an epoxy adhesive.

4. An adhesive structure in which a first vulcanized rubber and a second vulcanized rubber are bonded together via an adhesive layer, the adhesive structure being manufactured by the manufacturing method according to any one of claims 1 to 3, the adhesive layer contains a urethane compound and / or an epoxy compound, A bonded structure, wherein at least a portion of the surfaces of the first vulcanized rubber and the second vulcanized rubber that come into contact with the adhesive layer is chlorinated.

5. The adhesive structure according to claim 4, wherein the first vulcanized rubber and the second vulcanized rubber have rubber molecules present on their surfaces in contact with the adhesive layer that have hydroxyl groups, and the hydroxyl groups are bonded to carbon atoms that constitute the rubber molecules.

6. 6. The adhesive structure according to claim 4, wherein the first vulcanized rubber and the second vulcanized rubber have a concentration of an aromatic secondary amine-based antioxidant of 1% by mass or less in a region 10 μm deep from the surface in contact with the adhesive layer.

7. A tire comprising the adhesive structure according to any one of claims 4 to 6.

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