Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1998-01-05
2001-12-11
Gallagher, John J. (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S137000, C156S153000, C156S249000, C156S303100, C156S304500, C156S307100, C156S307300
Reexamination Certificate
active
06328840
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a process for adhering vulcanized rubbers to each other and a process for adhering a vulcanized rubber and an unvulcanized rubber. The present invention also relates to processes for producing various types of rubber products, such as a large size rubber weir, a steep slope belt conveyor, a rubber gasket used for a joint portion of immersed elements for an immersed tunnel, and a retreaded tire, by using the processes for adhering.
PRIOR ART OF THE INVENTION
Heretofore, as a process for adhering vulcanized rubbers to each other, such as a process used for producing a conveyor belt or a rubber track having an endless structure by bonding two end portions of an intermediate product having ends, processes comprising the steps of treating surfaces for adhering vulcanized rubbers with buffing to form a rough surface, coating the treated surfaces with an adhesive composition such as a rubber cement, inserting an unvulcanized rubber between the coated surfaces, and vulcanizing the resultant laminate, are generally and frequently used.
However, it is difficult to completely remove dust formed by the treatment of buffing when a surface of a vulcanized rubber is treated with buffing, and the dust remaining on the surface makes it difficult to achieve complete adhesion. The conventional processes have another problem that the working environment deteriorates because coating of the surface for adhesion with an adhesive material such as a rubber cement is necessary. In a process intended to solve the problem, the surface for adhesion of a rubber article is left in an unvulcanized condition while other parts of the article are vulcanized, and then, the unvulcanized surface is brought into contact with a similar unvulcanized surface of another article of a vulcanized rubber, and the two articles of vulcanized rubbers are bonded to each other by vulcanizing them together.
However, the process described above has drawbacks in that demolding of the article having the unvulcanized surface after vulcanization of the other parts is difficult because of the unvulcanized condition of the surface, and that, when for example an article is made into an endless form, handling of the unvulcanized surface and operations of the adhesion must be conducted with extreme care because the unvulcanized part is tacky.
A process for adhering a vulcanized rubber and an unvulcanized rubber to each other is used, for example, in a process for producing a slope conveyor belt or the like. For producing a slope conveyor belt, a flat conveyor belt is prepared in advance. For preparation of a slope conveyor belt, rubber parts which are used for making an uneven surface structure necessary for a slope belt, such as rubber cleats, are attached in an unvulcanized condition to the vulcanized flat conveyor belt which has been prepared in advance. The flat belt and the rubber parts are then bonded to each other by vulcanization. In conventional processes for producing a rubber product having an uneven structure like a slope conveyor belt, producing the rubber product integrally in a single step causes problems that a large amount of investment or a large area is required to install facilities for vulcanizing the product, that conditions of the operation become extremely complicated, and that it is very difficult to achieve uniform vulcanization. Therefore, products such as those described above are produced according to the steps comprising preparing a simpler vulcanized rubber product such as a flat conveyor belt in advance, then preparing parts of protrusion and other parts forming the uneven structure, such as cleats of a slope conveyor belt and the like, by using unvulcanized rubbers, and subsequently bonding the vulcanized rubber product and the parts of protrusion of unvulcanized rubbers to each other by vulcanizing together. In processes generally and frequently used for adhering a vulcanized rubber and an unvulcanized rubber such as those used in the processes described above, the surface for adhesion of a vulcanized rubber is coated with an adhesive composition such as a rubber cement after the surface is treated with buffing to form a rough surface, and then an unvulcanized rubber is attached to the coated surface and vulcanized to achieve the adhesion.
However, the process for adhering a vulcanized rubber and an unvulcanized rubber has the same problems as those in the process for adhering vulcanized rubbers to each other described above. Furthermore, when an unvulcanized rubber containing sulfur in the same amount as that in the vulcanized rubber is used, sulfur migrates from the unvulcanized rubber to the vulcanized rubber through the interface of adhesion during and after the process for adhering, and decrease in the hardness (decrease in the adhesive strength) at the surface of adhesion occurs.
Prior arts relating to processes for producing various rubber products which require a process for adhering vulcanized rubbers to each other or a process for adhering a vulcanized rubber and an unvulcanized rubber as an indispensable step are described in the following.
A rubber weir of a bag shape expands due to fluid being filled therein and forms a weir across a river. It contracts due to discharge of the fluid therefrom and allows river water flow freely. Production of a large size rubber weir requires a large amount of investment for production facilities, such as a large area for production and equipments of large sizes when the rubber weir is produced by vulcanizing it as a integral single body. Therefore, according to heretofore disclosed processes (Japanese Patent Publication No. Heisei 3(1991)-35098, Japanese Patent Application Laid-Open No. Heisei 6(1994)-226850), a large size rubber weir is generally produced by preparing weir segments which are portions of the rubber weir formed by dividing the rubber weir in the circumferential direction, and then are bonded to each other. Each weir segment is prepared by adhering vulcanized rubber plates containing a reinforcing fabric to each other (for example, part
26
in FIG.
8
).
A stepped structure is used in both processes described above in order to increase adhesion of end portions of the rubber plates as is shown in
FIG. 9. A
stepped structure is formed at the end portions of the rubber plates
011
which have been vulcanized, and the rubber fragment at the stepped structure is removed. A rubber sheet
012
containing a reinforcing fabric or an unvulcanized rubber containing a reinforcing fabric which has a shape fitting the stepped structure of the rubber plates is prepared separately. The rubber sheet (through an unvulcanized rubber when the rubber sheet has been vulcanized) or the unvulcanized rubber is fitted to a depression formed by abutting the two end parts of the rubber plates having the stepped structure as is shown in
FIG. 5. A
rubber weir segment is prepared by bonding the rubber plates to each other through adhesion of the components of the resultant laminate by vulcanization. The processes described above have a big problem in the bonding of rubber plates to each other.
In the processes described above, a process for forming the stepped structure at the end portion of the rubber plate
011
which has been vulcanized is necessary. It is important in the process for forming the stepped structure that adhesion by vulcanization which does not cause separation or fracture at the surface of adhesion is achieved by separating layers in the rubber plate exactly at a rubber layer between reinforcing layers when the stepped structure is formed, and by fitting the vulcanized rubber sheet containing a reinforcing fabric or the unvulcanized rubber sheet
012
containing a reinforcing fabric (in recent processes) exactly to the surface of the stepped structure.
In order to separate layers in the rubber plate exactly at a rubber layer, the process for the formation of the stepped structure heretofore contains a procedure of peeling part
12
in
FIG. 3
by fully employing an apparatus or a technique speci
Ieyoshi Masanao
Iizumi Shingo
Kato Shingo
Takada Hiroshi
Takano Nobukazu
Bridgestone Corporation
Gallagher John J.
Oliff & Berridg,e PLC
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