Metal fusion bonding – Process – With protecting of work or filler or applying flux
Reexamination Certificate
1999-11-17
2001-05-22
Ryan, Patrick (Department: 1725)
Metal fusion bonding
Process
With protecting of work or filler or applying flux
C228S262430
Reexamination Certificate
active
06234381
ABSTRACT:
OBJECTS AND SUMMARY OF THE INVENTION
1. Technical Field
Firstly, the present invention relates to a water-based binder that is used when brazing aluminum materials. This binder has excellent heat decomposition, room temperature adhesion, viscosity stability, and resistance against processing oil, and the like. Secondly, the present invention relates to a brazing composition that is a mixture, comprising: this water based binder and flux, or this water based binder, flux, and a brazing material. This brazing composition is not flammable or explosive because it is water-based. It has good wettability and can form a uniform coating on the aluminum material. Thirdly, the present invention relates to a brazing method for aluminum materials using this brazing composition.
2. Background Technology
In the prior art, almost all engine radiators and condensers and evaporators for car air conditioners are manufactured from aluminum materials. The aluminum materials are joined together through brazing.
Recently, because of concerns over productivity, flux brazing methods in which brazing is conducted using flux has become mainstream, replacing the vacuum brazing method which does not use flux. In this flux brazing method, flux, such as fluoroaluminate, or a mixture in which brazing material is added to this flux (in other words, the brazing composition) needs to be supplied to the brazing sites of the aluminum material. In order to improve the adhesion to the aluminum material, coating ofthis brazing composition is conducted after various binders have been added.
For these binders, oil-based binders in which various organic resins are dissolved in organic solvents such as alcohol, toluene, acetone, and the like, and water-based binders comprising water based organic resins have been used or reported.
When aluminum materials are coated using the oil-based binders as described above, there is good adhesion to the aluminum materials, and excessive cissing phenomenon is not seen. Uniform coating with the brazing composition is also achieved. However, because organic solvents are used, it can be flammable or explosive when used. In order to avoid these risks, expensive explosion-proof devices are needed. Furthermore, working with organic solvents in the air can pose many health problems.
On the other hand, when using water-based binders, these are not flammable or explosive, but because water is used as a solvent, the wetting onto the aluminum is extremely poor, and because of cissing of the water on the aluminum material, it is difficult to have a uniform coating of the brazing composition.
For example, in Japanese Laid-Open Patent Publication Number 6-285682 (hence referred to as the prior art technology), there is disclosed a brazing composition that uses a water-soluble organic resin, such as acrylic resin, cellulose resin, epoxy resin, polyvinyl alcohol resin, and the like, as the main component of the binder. However, in general, water-based binders that have water soluble resins as their main component have poor heat decomposition. When brazing, carbides can remain and can cause corrosion. Fillets are not well-formed, and this can have a negative impact on brazing.
Normally, when manufacturing brazed products, after coating the aluminum materials with the brazing composition, various processing of aluminum materials is conducted prior to brazing. This processing of aluminum can include press processing for adjusting the thickness, bending, or stretching or the like.
After the aluminum materials are coated with the brazing composition in which the binders from the prior art are added, various problems often arise for both oil-based and water-based binders when the above processing is conducted. The brazing composition can fall off of the aluminum material, cracks can be generated at the surface, or if aluminum materials are stacked, there can be blocking together of the aluminum materials. In addition, because hydrocarbon organic solvents such as cutting oil and press processing oil and the like are used when working with aluminum material, the binder can become dissolved in these organic solvents, and the brazing composition can fall off.
Furthermore, in this prior art technology, when water soluble organic resins such as acrylic resins are used as the binder for the flux, if melamine resin or benzoguanamine resin, or the like are added as the hardening agent to this water soluble organic resin, the adhesion to the aluminum material has been shown to be improved. In order to prevent the brazing composition from falling off through contact with organic solvents or through the above processing, the use of this technology of hardening binder can be considered. However, in reality, when such a heat curing binder is used, while the brazing composition is applied to the aluminum material, or while the manufactured brazing composition is being stored, this composition thickens as time passes, and the coating operation becomes difficult.
The object of the present invention is to develop a new binder for aluminum brazing and a brazing composition to which this binder has been added. The present invention has excellent properties of thermal decomposition when brazing, room temperature adhesion to the aluminum material, viscosity stability during coating or storing, and oil resistance against processing oil and the like. There is also no risk of catching on fire or of explosion. The present invention also has good wettability onto aluminum materials.
According to an embodiment of the present invention, there is provided a water based binder for brazing aluminum materials comprising: an ester methacrylate polymer; the ester methacrylate polymer having a glass transition temperature between about −30° C. to 60° C., and an acid value between about 20 to 80 when dry; the ester methacrylate polymer capable of being saponified by a compound having cationic properties in an aqueous solution; and the ester methacrylate polymer capable of forming an aqueous solution with a solid concentration of between about 1 to 50 weight percent.
According to another embodiment of the present invention, there is provided an aluminum brazing composition comprising: from about 1 to 50 parts by weight of a water based binder; the water based binder being an ester methacrylate polymer having a glass transition temperature between about −30° C. to 60° C. and an acid value between about 20 to 80 when dry; the ester methacrylate polymer capable of being saponified by a compound having cationic properties in an aqueous solution; and the ester methacrylate polymer capable of forming an aqueous solution with a solid concentration of between about 1 to 50 weight percent.
According to a further embodiment of the present invention, there is provided a method for brazing aluminum materials, comprising: contacting a brazing composition with at least a portion of at least one of a first aluminum material and a second aluminum material; the brazing composition having from about 1 to 50 parts by weight of a water based binder; the water based binder being an ester methacrylate polymer having a glass transition temperature between about −30° C. to 60° C. and an acid value between about 20 to 80 when dry; the ester methacrylate polymer capable of being saponified by a compound having cationic properties in an aqueous solution; the ester methacrylate polymer capable of forming an aqueous solution with a solid concentration of between about 1 to 50 weight percent; supplying flux to at least one of the first aluminum material and the second aluminum material; assembling the first aluminum material and the second aluminum material into a specified configuration; and heating and brazing the first aluminum material with the second aluminum material.
In order to develop a new binder for adding to a brazing composition for aluminum materials, we mainly studied various organic resins for their suitability as a binder for brazing. As a result, it has been discovered that acrylic or methacrylic resins are suitable as binders.
Next,
Hasegawa Yoshiharu
Shibata Hikaru
Taninaka Ichiro
Teshima Shoei
Denso Corporation
Johnson Jonathan
Morrison Law Firm
Ryan Patrick
LandOfFree
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