Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2001-05-16
2004-06-15
Sellers, Robert (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C523S459000, C523S468000, C525S124000, C525S127000, C525S151000, C525S182000, C525S208000, C525S327200, C525S423000, C525S502000, C525S503000, C525S504000, C525S506000, C525S510000, C525S523000
Reexamination Certificate
active
06750274
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to curable, weldable coatings for metal substrates, and more particularly, to curable, weldable coatings for metal substrates, which inhibit corrosion.
BACKGROUND OF THE INVENTION
The production of light gauge steel for end uses ranging from architectural construction materials to automobiles is well known. A rolling mill line produces continuous sheets of steel in the required thickness and width. The steel sheets may be coated with a thin layer of zinc metal via a galvanizing process. Eventually, mill oil is applied to the uncoated or galvanized steel sheets, and the steel is either stored or shipped in a coil to a customer for further processing.
Typically, the customer is an automobile manufacturer who will take the coiled metal sheet and pass it through a lubricating station and then to a forming operation where the metal sheet is cut and formed into a part such as a roof, fender, door, etc. The parts are then welded together to form an automobile body. Next, the automobile body is cleaned, treated with a zinc phosphating solution to enhance corrosion protection, and rinsed with deionized water. The treated automobile body is then passed through an electrodeposition bath where a corrosion resistant primer is applied.
The automobile manufacturers would like to streamline their operations and have some of the operations described above done outside the automobile assembly plant, for example at a steel mill or a custom coater. One major problem with moving certain operations to a steel mill or a custom coater is that any coating applied outside the automobile assembly plant must be able to accept a weld. At some point in time, the various metal parts will be welded together in the automobile assembly plant to form the automobile body. Consequently, automobile manufacturers have a strong demand for a weldable, corrosion resistant coating composition that can be applied at a steel mill or at a custom coating facility.
Such a weldable, corrosion resistant coating composition could be applied at a custom coater, known as a coil coater, who would ship the coated metal sheet to the automobile manufacturer. As described above, the automobile manufacturer would then form the metal sheet into parts and weld the parts together. However, the metal pretreatment operation and perhaps the electrodeposition process could be avoided since the metal received by the automobile manufacturer would already contain a corrosion resistant coating.
Similar to the above, a weldable, corrosion resistant coating composition could also be applied at a steel mill. Application at the steel mill enables the automobile manufacturer to receive corrosion resistant metal directly without the expense associated with shipping the metal to a coil coater and from the coil coater to the automobile manufacturer.
The present invention provides a weldable, curable coating composition that provides corrosion protection and can be applied by a coil coater or at a steel mill, can be cured at low temperature and provides good adhesion and good corrosion protection without prior metal pretreatment.
SUMMARY OF THE INVENTION
One aspect of the present invention is a curable coating composition comprising:
a. a resinous binder comprising:
i. a reaction product of an epoxy-containing polymer with a compound containing phosphorus acid groups, the reaction product having reactive functional groups,
ii. a curing agent having functional groups reactive with the functional groups of (i);
b. an electroconductive pigment dispersed in (a) such that the weight ratio of b to (i) plus (ii) is within the range of 0.5 to 9.0:1,
the curable coating composition being characterized such that when it is deposited and cured on a metal substrate, the cured coating is weldable.
Another aspect of the present invention is an aqueous-based coating composition comprising:
a. a resinous binder comprising:
i. a reaction product of an epoxy-containing polymer with a compound containing phosphorus acid groups, the reaction product having reactive functional groups,
ii. a curing agent having functional groups reactive with the functional groups of (i);
b. an electroconductive pigment dispersed in (a) such that the weight ratio of b to (i) plus (ii) is within the range of 0.5 to 9.0:1; and
c. water,
the coating composition being characterized such that when it is deposited and cured on a metal substrate, the cured coating is weldable.
Yet, another aspect of the present invention is an organic solvent-based coating composition comprising:
a. a resinous binder comprising:
i. a reaction product of an epoxy-containing polymer with a compound containing phosphorus acid groups, the reaction product having reactive functional groups,
ii. a curing agent having functional groups reactive with the functional groups of (i);
b. an electroconductive pigment dispersed in (a) such that the weight ratio of b to (i) plus (ii) is within the range of 0.5 to 9.0:1; and
c. an organic solvent,
the curable coating composition being characterized such that when it is deposited cured on a metal substrate, the cured coating is weldable.
Another aspect of the present invention is a process for coating a continuous strip or coil of metal comprising:
a. applying directly to the metal sheet shortly after it is formed and at a temperature of 20 to 150° C., a curable coating composition comprising:
i. a resinous binder comprising
(A) a reaction product of an epoxy-containing polymer with a compound containing phosphorus acid groups, the reaction product having reactive functional groups,
(B) a curing agent having functional groups reactive with the functional groups of (A);
ii. an electroconductive pigment dispersed in (i) such that the weight ratio of (ii) to (A) plus (B) is within the range of 0.5 to 9.0:1,
the curable coating composition being characterized such that when it is deposited and cured on a metal substrate, the cured coating is weldable; and
b. drying the coating composition on the metal sheet.
Yet, another aspect of the invention is a process for coating a continuous metal coil comprising:
a. unwinding the metal sheet from a metal coil and passing the metal sheet in a substantially continuous manner through a cleaning station, a coating station, and a curing station;
b. applying to the metal sheet at the coating station a curable coating composition comprising:
i. a resinous binder comprising:
(A) a reaction product of an epoxy-containing polymer with a phosphorus-containing acid, the reaction product having reactive functional groups,
(B) a curing agent having functional groups reactive with the functional groups of (A);
ii. an electroconductive pigment dispersed in (i) such that the weight ratio of (ii) to (A) plus (B) is within the range of 0.5 to 9.0:1; and
C. curing the coating composition applied to the metal sheet in step (b) as the coated metal sheet passes through the curing station.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The use of numerical values in the various ranges specified in this application, unless expressly indicated otherwise, are stated as approximations as though the minimum and maximum values within the stated ranges are both preceded by the word “about”. In this manner, slight variations above and below the stated ranges can be used to achieve substantially the same results as values within the ranges. Also, the disclosure of these ranges is intended as a continuous range including every value between the minimum and maximum values.
The present invention is a curable coating composition for metal substrates that can be applied without pretreatment and methods involving the same. The curable coating composition comprises a resinous binder. The resinous binder comprises a reaction product of an epoxy-containing polymer with a compound containing phosphorus acid groups. The reaction product has reactive functional groups.
Useful epoxy-containing polymers have at least one epoxy or oxirane group in the molecule, such as polyglycidyl ethers of polyhydric alcohols. Useful polyglycidyl et
Coldren Kathleen M.
Gray Ralph C.
Jones Dennis W.
Jones James E.
Nugent, Jr. Richard M.
Miles Jacques B.
PPG Industries Ohio. Inc.
Sellers Robert
Uhl William J.
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