JPS6359860B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a conductive crosslinking bonding method. The conventional cross-linking bonding method of vulcanized rubber and vulcanized rubber involves interposing an intermediate layer of thermally crosslinkable rubber (unvulcanized rubber composition) between the vulcanized rubber and the upper and lower layers. In this method, heat is applied from the vulcanized rubber layer of the vulcanized rubber layer, and the heat transmitted through the vulcanized rubber layer crosslinks the intermediate layer and at the same time bonds the intermediate layer and the vulcanized rubber layer. Since the heat source is external, it is necessary to heat the press and mold, and the vulcanized rubber layer, which does not need to be heated, must be heated for a long time, which requires a lot of wasted thermal energy. There are disadvantages in terms of economy. The present inventors previously used a thermally crosslinkable conductive rubber containing conductive carbon black in the intermediate layer as a conductive crosslinking bonding method between vulcanized rubber and applied a voltage to the intermediate layer. He proposed a method in which the intermediate layer was heated by itself, and the intermediate layer was vulcanized by the generated heat, and at the same time, the vulcanized rubber was bonded together.
No. 59168 (Japanese Unexamined Patent Publication No. 56-15574)). However, after conducting various studies, we found that if the upper and lower vulcanized rubbers are not flat plates, the pressure distribution will be different during pressurization, rubber flow will occur, the sheet gauge of the thermally crosslinkable rubber composition will change, and heat generation will be uneven. I made sure of that. As a result of intensive research to further solve this problem, the inventors of the present invention solved the above drawback by using conductive vulcanized rubber as the heating element.
The present invention was accomplished by discovering that two vulcanized rubbers can be crosslinked and bonded successfully. In the present invention, a conductive vulcanized rubber having a volume specific resistivity of 10 ⁴ Ω·cm or less in a temperature range of 0 to 200°C is interposed between the vulcanized rubber, and at least one of the above-mentioned An intermediate layer of a thermally crosslinkable rubber composition (unvulcanized rubber composition) is interposed between the vulcanized rubber and the conductive vulcanized rubber, and a voltage is applied to the conductive vulcanized rubber.
The present invention relates to a conductive crosslinking bonding method characterized by cross-curing an intermediate layer and simultaneously bonding upper and lower vulcanized rubbers by self-heating of the conductive vulcanized rubber. The present invention will be explained in detail below. Carbon blacks to be blended into the conductive vulcanized rubber in the present invention include furnace blacks such as SAF, ISAF, and HAF, thermal blacks such as TT and MT, which are commonly blended into rubber, EPC,
Channel blacks for MPC, etc., and conductive carbon blacks such as Ketschen Black EC (product of Akzo in the Netherlands), Vulcan XC-72, Vulan
SC, Vulcan C (both products from CABOT, USA)
Examples include conductive furnace black such as Asahi HS-500 (product of Asahi Carbon Co., Ltd.) and conductive acetylene black such as Denka Black (product of Denki Kagaku Kogyo Co., Ltd.). Among these, conductive furnace blacks, especially buttress blacks EC, are preferably used. Carbon black must be blended in an amount such that the specific volume resistivity of the conductive vulcanized rubber is 10 ⁴ Ω·cm or less in the temperature range of 0 to 200°C. If the specific volume resistivity exceeds 10 ⁴ Ω·cm, it is unsuitable because a high voltage or a long time is required to raise the temperature to the temperature required for crosslinking. In order to reduce the specific volume resistivity to 10 ⁴ Ω・cm or less, it varies slightly depending on the type of carbon black, but when using conductive carbon black, it is usually necessary to At least 7 parts by weight may be added. Also, carbon black (HAF, etc.) used in ordinary rubber compounding.
When using, at least 45 parts by weight may be added. The lower the specific volume resistivity, the more advantageous it is for heat generation, but on the other hand, if too much carbon black is blended, the physical properties will drop significantly, so the rubber component
It is preferable to limit the amount to 80 parts by weight or less per 100 parts by weight. Of course, furnace blacks such as SAF, ISAF, HAF, channel blacks such as EPC, MPC, thermal blacks such as FT, TT, etc.
It is also possible to use it by blending it with more than one kind of conductive carbon black. Rubber components of conductive vulcanized rubber include natural rubber, diene rubbers such as butadiene rubber, isoprene rubber, and chloroprene rubber, diene copolymer rubbers such as styrene-butadiene rubber and acrylonitrile-butadiene rubber, butyl rubber, and halogenated butyl rubber. Olefin-based rubbers such as , ethylene-propylene-based rubbers are preferably used; in addition, organosilicon-based rubbers that are alkylsiloxane condensates, fluorine-based rubbers such as vinylidene fluoride-propylene hexafluoride copolymers, alkylene rubbers, etc. Polysulfide rubbers such as sulfide polymers, vinyl rubbers such as acrylic acid ester polymers, and urethane rubbers are used. These rubbers can be used alone or in combination of two or more. As for the rubber components of the vulcanized rubber and thermally crosslinkable rubber composition to be bonded, those exemplified as the rubber components of the conductive vulcanized rubber can be similarly used. The thermally crosslinkable rubber composition used for the intermediate layer is
Various crosslinking methods can be employed. Most preferably used is sulfur vulcanization (adding a vulcanization accelerator if necessary). Examples of crosslinking agents other than sulfur vulcanization include p-quinonedioxime, p,p'-dibenzoylquinonedioxime, 4,4'-dithiodimorpholine, poly-p-dinitrobenzene, and ammonium benzoate. Organic vulcanizing agents used for vulcanization: dicumyl peroxide, 1,1-bis(t-butylperoxy)3,3,5-trimethylcyclohexane, α,α'-bis(t-butylperoxyisopropyl) Organic peroxides such as benzene, resin crosslinking agents such as methylolated or brominated alkylphenol resins, organic polyvalent amines such as triethylenetetramine, hexamethylene diamine carbamate, and metals such as magnesium oxide, lead oxide, and zinc oxide. Oxides and the like are preferably used. Of course, it is also possible to use other known crosslinking agents. To the thermally crosslinkable rubber composition of the intermediate layer, ordinary rubber compounding agents such as vulcanization accelerators, accelerators, anti-aging agents, reinforcing agents, softeners, tackifiers, etc. can be optionally added depending on the purpose of use. can do. Next, the procedure of conductive cross-linking adhesion of the present invention will be illustrated. The illustrated example is vulcanized rubber A and conductive vulcanized rubber B.
This also shows a method of bonding vulcanized rubber A' and conductive vulcanized rubber B at the same time.As shown in Figure 1, between vulcanized rubber A, A' and conductive vulcanized rubber B Intermediate layers C and C' of a thermally crosslinkable rubber composition are interposed between the electrodes D attached to both ends of the conductive vulcanized rubber B while the vulcanized rubber is pressed together.
A voltage is applied from an AC or DC power source P. The voltage applied during conductive cross-linking adhesion is determined by the specific volume resistivity of the conductive cross-linked rubber, the cross-sectional area of the conductive cross-linked rubber, the length between the electrodes, the temperature required for cross-linking, etc. A range of ~400V is preferred.
The temperature required for crosslinking is usually in the range of 80 to 200°C, but the desired temperature is reached within a short time after voltage application. Further, by changing the applied voltage, the temperature during crosslinking can be arbitrarily changed, and various reactions can be easily controlled depending on the properties of the crosslinking agent in the intermediate layer. The mold surface of vulcanized rubber may be used as the adhesive surface, but in order to improve the adhesive strength, organic acids,
It is preferable to apply cement by chemical treatment using an inorganic acid or by mechanical buffing. As described above, according to the present invention, when adhering vulcanized rubber to vulcanized rubber, an intermediate layer of a thermally crosslinkable rubber composition is interposed, and a voltage is applied to the conductive vulcanized rubber. Because cross-linking can be achieved by self-heating,
There is no need for an external heat source, so there is no need to heat the press or mold, and the generated heat can be used efficiently, resulting in significant benefits in terms of energy costs. The conductive cross-linking bonding method of the present invention can be applied to fenders and tires for construction vehicles, which require uniform temperature distribution, especially when vulcanizing thick materials, and to retreading tires where the vulcanized rubber is not a flat plate. . The invention will be further illustrated by the following examples and comparative examples. Examples 1 to 3 As shown in Table 1, conductive vulcanized rubber sheets having a thickness of 2 to 6 mm and containing different amounts of carbon black were obtained by ordinary press vulcanization. The specific volume resistivities of these were in the range of 3 Ω·cm to 8×10 ³ Ω·cm. As the vulcanized rubber to be bonded, the 2 mm thick vulcanized rubber sheet used in the comparative example was used. As for the treatment of the adhesive surface, both the conductive vulcanized rubber and the vulcanized rubber were buffed and then washed with n-hexane before use. The intermediate unvulcanized rubber sheet was a 1 mm thick unvulcanized rubber sheet containing 100 parts by weight of natural rubber, 40 parts by weight of carbon black (HAF), and a sulfur compound. Measurement of specific volume resistivity of conductive vulcanized rubber is
It was carried out according to ASTMD991-60. The adhesive strength was evaluated using a T-peel test in accordance with JIS K6854, using a sample width of 25 mm and a tensile speed of 50 mm/
It was carried out under conditions of min. As shown in Figure 2, the peel test piece had a five-layer structure with intermediate unvulcanized rubber layers C and C' interposed between vulcanized rubber A and A' and conductive vulcanized rubber B. A pressure of 5 kg/cm ² was applied, a voltage was applied to electrodes D at both ends so that the temperature of the intermediate layer was 150° C., and vulcanization bonding was performed for a predetermined time. The results are shown in Table 1. As is clear from the results in Table 1, vulcanized rubber A,
A' and B were sufficiently vulcanized and bonded under these conditions. Comparative example 1 Carbon black (HAF) as shown in Table 1
The volume resistivity of the vulcanized rubber containing 40 parts by weight per 100 parts by weight of rubber was 5×10 ⁴ Ω·cm. Using the same procedure as in Examples 1 to 3, the thickness of the conductive vulcanized rubber was 6 mm, the distance between the electrodes was 50 mm, and the length of the electrodes was 100 mm.
When a voltage of 400V was applied for 30 minutes, the temperature of the intermediate unvulcanized rubber was 50°C and was not vulcanized.

【table】

[Table] Example 4 As shown in Figure 3, an integrated body of conductive vulcanized rubber B and vulcanized rubber A and vulcanized rubber A' with embedded steel cords were created by normal press vulcanization using a mold. did. The shape of conductive vulcanized rubber B to which electrode D is vulcanized and bonded is 1.5 mm thick, 25 cm distance between electrodes, and 33 cm long.
cm. A plus plated steel cord with a diameter of 1.15 mm was used as an electrode. The electrode was placed 3 cm outside of vulcanized rubber A. For the vulcanized rubber A', 106 steel cords/19 cm with a diameter of 1.15 mm were embedded at a depth of 1 to 1.5 mm from the adhesive surface parallel to the electrodes. For the formulation of conductive vulcanized rubber B, the formulation of Example 2 in Table 1 was used. The formulations of vulcanized rubbers A and A' were the same as those used in Comparative Example 1 in Table 1. The method of conductive cross-linking adhesion is as shown in Fig. 4, where conductive vulcanized rubber B and vulcanized rubber A are integrated,
A non-conductive unvulcanized rubber sheet C with a thickness of 1 mm is interposed between A' and 2.
A pressure of Kg/cm ² was applied, and the conductive vulcanized rubber B was energized and heated to effect vulcanization and adhesion. To treat the adhesive surface, both conductive vulcanized rubber B and vulcanized rubber A' were buffed and then washed with n-hexane. The composition of the non-conductive unvulcanized rubber is 40 parts by weight of carbon black (HAF) per 100 parts by weight of natural rubber.
A sulfur-containing rubber was used. Current conditions were an applied voltage of 70 V and a temperature increase of 150° C. in 10 minutes. After raising the temperature, vulcanization bonding was performed for 30 minutes. Adhesive strength evaluation is JIS K6854
A T-peel test was conducted in accordance with the above, with a sample width of 25 mm cut out and a tensile speed of 50 mm/min. The adhesive force was 65 kg/25 mm, and the intermediate layer rubber was destroyed, indicating sufficient vulcanization adhesion.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional schematic diagram showing the cross-linking bonding method of the present invention, Fig. 2 is a sketch showing the method for producing a T-shaped peel test piece, Fig. 3 is a sketch of the vulcanized rubber to be bonded, and Fig. 4 is an example. FIG. 4 is a sketch showing the cross-linking bonding method of No. 4. A, A'... Vulcanized rubber, B... Conductive vulcanized rubber,
C, C'...thermally crosslinkable rubber composition, D...electrode, E
...Steel cord, P...Power supply.

Claims (1)

[Claims] 1. A conductive vulcanized rubber having a volume specific resistivity of 10 ⁴ Ω·cm or less in the temperature range of 0 to 200°C is interposed between the vulcanized rubber, and further, An intermediate layer of a thermally crosslinkable rubber composition is interposed between at least one of the vulcanized rubber and the conductive vulcanized rubber, a voltage is applied to the conductive vulcanized rubber, and the conductive vulcanized rubber self-generates heat. A conductive cross-linking bonding method for vulcanized rubber and vulcanized rubber, characterized in that the intermediate layer is cross-linked and the upper and lower vulcanized rubbers are bonded to each other at the same time. 2. The conductive crosslinking bonding method according to claim 1, wherein the vulcanized rubber imparted with conductivity is blended with carbon black. 3. The conductive crosslinking bonding method according to claim 1, wherein the carbon black blended into the conductive vulcanized rubber is a conductive furnace black. 4. The conductive crosslinking bonding method according to claim 1, wherein the amount of conductive furnace black in the conductive vulcanized rubber is 7 to 80 parts by weight per 100 parts by weight of rubber.