Coating processes – Restoring or repairing – Metal article
Reexamination Certificate
2001-02-15
2002-04-09
Beck, Shrive P. (Department: 1762)
Coating processes
Restoring or repairing
Metal article
C427S140000, C427S410000, C427S407100
Reexamination Certificate
active
06368661
ABSTRACT:
The present invention relates to a method for repair coating which is capable of forming a coating film having a good performance when coated on a deteriorated coating film surface of a coating film formed from a tar epoxy resin coating material, a tar urethane resin coating material, a modified epoxy resin coating material, a modified urethane resin coating material, an epoxy-polyamine resin coating material or an epoxy urethane resin coating material, without removing the deteriorated layer on the deteriorated coating film.
In large size steel structures such as marine vessels and bridges which are exposed to a corrosive environment, high corrosion-protective coating materials such as a tar epoxy resin coating material, a tar urethane resin coating material, a modified epoxy resin coating material, a modified urethane resin coating material, an epoxy-polyamine resin coating material and an epoxy urethane resin coating material are coated on upper structures, decks, holds, ballast tanks, cargo tanks and outside plates of marine vessels; and outside plates, girder outside surfaces and girder inside surfaces of bridges from a viewpoint of corrosion protection.
These large size steel structures have usually as long building and constructing periods as 3 to 24 months, and therefore coating films of a tar epoxy resin coating material, a tar urethane resin coating material, a modified epoxy resin coating material, a modified urethane resin coating material, an epoxy-polyamine resin coating material and an epoxy urethane resin coating material are usually exposed in an outdoor for not much longer than 1 to 12 months.
In general, the coating films of these resin bases are inferior in a weatherability, and a deterioration of the coating films such as discoloration, glaze reduction and chalking is brought about if they are exposed in an outdoor over a long period of time. This deterioration is notably observed in the coating film of a tar epoxy resin coating material or a tar urethane resin coating material.
If a prescribed coating material is applied directly on coating films which are formed by applying the coating materials of the resin bases described above and which are exposed in an outdoor over a long period of time during building, constructing or using and deteriorated, an adhesive property between this applied coating film and the deteriorated coating films is markedly inferior, and therefore brought about is the defect that the problems of cracking and peeling are caused many times during a building, constructing or using period.
With respect to a countermeasure therefor, when a coating material is applied on the deteriorated coating film described above, a deteriorated layer on the surface of the resin base coating film described above is removed by blast treatment or removing treatment using a power tool, a hand tool or high pressure washing, and then a prescribed coating material is applied. However, a lot of labor and cost is required for removing this deteriorated coating film, and therefore strongly desired to be developed are a coating material and a coating method capable of forming a coating film having a good corrosion prevention on the above deteriorated coating film without providing such removing step and causing the problems of cracking and peeling on the above deteriorated coating film.
Further, the coating films of the resin bases described above are deteriorated not only by exposure but also by submerging. If a prescribed coating material is applied on a coating film which is deteriorated by submerging without treating the deteriorated coating film, an adhesive property between the applied coating film and the deteriorated coating films is markedly inferior, so that the problems of cracking and peeling are brought about many times during a building, constructing or using period.
An object of the present invention is to provide a method for repair coating which is capable of forming a coating film having good performances such as an adhesive property even if coated on a deteriorated coating film surface of a coating film formed by applying a tar epoxy resin coating material, a tar urethane resin coating material, a modified epoxy resin coating material, a modified urethane resin coating material, an epoxy-polyamine resin coating material or an epoxy urethane resin coating material, without removing the deteriorated layer on the deteriorated coating film.
The present inventors paid attentions to the fact that in a deterioration phenomenon of a coating film caused by the outdoor exposure or submerging described above, a part of resin components (an epoxy resin, a curing agent and other jointly used resins) contained in the coating film was deteriorated to form a carboxyl group and considered that if the carboxyl group in this deteriorated coating film would be chemically bonded to a part of components of a coating material applied on the deteriorated coating film, an adhesive property between the coating films might be able to be improved. As a result of carrying out various investigations, it has been found, to be unexpected, that the object described above can be achieved by coating an epoxy resin-amine curing agent type coating composition on the deteriorated coating film whose water content is within a certain prescribed range.
Thus, the present invention provides a method for repair coating characterized by applying an epoxy-polyamine resin base coating composition comprising an epoxy resin having at least one epoxy group in a molecule and an amine base curing agent as resinous components on a deteriorated coating film which is selected from a tar epoxy resin coating film, a tar urethane resin coating film, a modified epoxy resin coating film, a modified urethane resin coating film, an epoxy-polyamine resin coating film and an epoxy urethane resin coating film and which has a moisture content of 0.3 to 5% by weight.
The method for repair coating of the present invention shall be explained below in further details.
The method for repair coating of the present invention is characterized by applying the epoxy-polyamine resin base coating composition on a specific kind of a deteriorated coating film having a prescribed moisture content.
In the method for repair coating of the present invention, the deteriorated coating film which is to be repaired is a coating film which is formed by applying a coating composition selected from a tar epoxy resin coating composition, a tar urethane resin coating composition, a modified epoxy resin coating composition, a modified urethane resin coating composition, an epoxy-polyamine resin coating composition and an epoxy urethane resin coating composition and which is exposed to various environments and deteriorated.
All of the tar epoxy resin coating material, the tar urethane resin coating material, the modified epoxy resin coating material, the modified urethane resin coating material, the epoxy-polyamine resin coating material and the epoxy urethane resin coating material each described above can be coating materials which are already known in the coating field of large size steel structures such as marine vessels, bridges and steel towers. The tar epoxy resin coating material includes, for example, a coating material comprising an epoxy resin and tar as resin components. The tar urethane resin coating material includes, for example, a coating material comprising a urethane resin and tar as resin components. The modified epoxy resin coating material includes, for example, a coating material comprising an epoxy resin and a modified resin (for example, a xylene resin, a toluene resin, a ketone resin, a coumarone resin, a petroleum resin, a phenol resin and a dicyclopentadiene resin; a carbonization residue such as tar, pitch and coal digested pitch; and a petroleum distillation residue such as asphalt) as resin components. The modified urethane resin coating material includes, for example, a coating material comprising a urethane resin and the modified resin described above as resin components. The epoxy-polyamine resin coat
Beck Shrive P.
Kansai Paint Co. Ltd.
Kolb Michener Jennifer
Wenderoth Lind & Ponack LLP
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