Stock material or miscellaneous articles – Composite – Of epoxy ether
Reexamination Certificate
2000-02-25
2001-07-24
Copenheaver, Blaine (Department: 1773)
Stock material or miscellaneous articles
Composite
Of epoxy ether
C428S354000, C156S278000
Reexamination Certificate
active
06265074
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to dry erasable boards. More particularly, the invention relates to coatings for erasable, markable surfaces for use with erasable marking pens.
2. Description of the Related Art
In the past, traditional classroom education relied entirely upon a “blackboard” and chalk as the medium for demonstrational instruction. This technique has proven to be relatively messy due to the chalk dust and smaller pieces of broken chalk. Blackboards were also limited in the range of chalk colors they could accept, due to their relatively dark color and the difficulty in completely erasing chalk colors other than white. One solution to this problem is the use of overhead projectors or laptop computers, but these units which provide graphics capability are relatively slow and costly for casual use.
A more economical solution to this problem is the use of dry erasable marking systems, or “dry erase boards”, which use erasable marking pens to provide the utility of a blackboard or chalkboard, while eliminating the mess of chalk dust and the difficulty of cleanup of multiple colors. Dry erase boards typically have a smooth, markable, coated writing surface formed by coating a substrate with a lacquer coating which is subsequently cured. Dry erase marking pens are typically felt tip marking instruments containing specially formulated inks which satisfactorily mark these coated writing surfaces, and can be substantially fully erased from these surfaces after the ink has dried. These dry-erase markers leave substantially no mess, and erasure typically requires only minimal manual effort using a conventional dry eraser, cloth, or paper tissue.
Previously developed dry-erase boards include writing surfaces made of coated paper or film, melamine, or ceramic which are adhered to smooth, hard, rigid substrates such as paper board, fiber board, plastic, wood, and the like. Coated paper and film based dry-erase surfaces are relatively inexpensive, however they suffer from a number of disadvantages. The erasable, markable character of these surfaces deteriorates gradually with repeated application and erasure of dry erasable inks. The chemical materials used to mark these surfaces often cause deformation of these surfaces, resulting in the formation of non-removable ghost images after continued use. These surfaces are also known to exhibit poor solvent resistance, and are often incompatible with certain dry erase markers. Ceramic based dry erase surfaces provide good erasability but are relatively expensive.
It would therefore be desirable to produce an inexpensive writable-erasable article which provides good erasability after continued use. The article of the present invention provides a solution to this problem. According to the invention, a substrate is coated with a specially formulated epoxy coating on one side, and an adhesive on another side. Surprisingly, the epoxy coating of the invention provides excellent erasability with substantially no ghosting images. It also exhibits good solvent resistance and is compatible with substantially all dry erase markers. The articles formed according to the invention may then be adhered to a support via an adhesive, and sold inexpensively to consumers in the form of a writable-erasable or “dry-erase” boards in a variety of sizes, depending on specific need.
SUMMARY OF THE INVENTION
The invention provides a write-erasable article which comprises a substrate having front and rear surfaces, a substantially non-tacky, non-porous, cured epoxy coating composition on the front surface of the substrate and an adhesive coating on the rear surface of the substrate.
The invention also provides a writable-erasable board which comprises a substrate having front and rear surfaces, a substantially non-tacky, non-porous, cured epoxy coating composition on the front surface of the substrate and an adhesive coating on the rear surface of the substrate.
The invention further provides a method of producing a writable-erasable board which comprises forming a substantially non-tacky, non-porous, cured epoxy coating composition on the front surface of a substrate; forming an adhesive coating on the rear surface of the substrate; and then attaching a support to the rear surface of the substrate via the adhesive coating.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The article of the present invention comprises a substrate coated with a cured epoxy coating composition on one surface and an adhesive coating on an opposite surface. This article may be used as a “dry erase board”.
The writable-erasable boards of the present invention may be produced by forming a substantially non-tacky, non-porous, cured epoxy coating composition on the front surface of a substrate, forming an adhesive coating on the rear surface of the substrate, and then attaching a support to the rear surface of the substrate via the adhesive coating.
The cured epoxy coating composition of the present invention is preferably substantially non-tacky and non-porous. This is to provide a surface which is easy to write on, while providing good erasability. The coating preferably comprises the reaction product of at least one epoxy polymer or epoxy precursor, at least one amine crosslinker, and at least one acid catalyst.
Optionally, but preferably, the epoxy coating composition contains an adhesion promoter and a solvent which is compatible with the other coating composition components.
The epoxy polymer or precursor of the present invention is one which has an epoxide equivalent weight of at least about 500 and preferably from about 500 to about 3,800.
Suitable epoxy polymers (or epoxy precursors) nonexclusively include
wherein n is at least 2 in order to have good solvent resistance. Preferred epoxy polymers include Dow DER 661 (equivalent epoxide weight of 525), Dow DER 662 (equivalent epoxide weight of 650), Dow DER 664 U (equivalent epoxide weight of 900), Dow DER 667 (equivalent epoxide weight of about 2000), Dow DER 668 and 669 (equivalent epoxide weight of 2300 to 3800), available commercially from Dow Chemical Company, and EPON 1001F (equivalent epoxide weight of 525), EPON 1002F, EPON 1004F, EPON 1007F and EPON 1009F, available commercially from Shell are also useful. The weight percentage of the uncured epoxy polymer in the epoxy coating ranges from at about 30% to about 70%, preferably from about 45% to about 65%, more preferably from about 50% to about 60% based on the weight of the epoxy coating composition solids.
The amine crosslinker of the current invention has the characteristics that it can be combined with the epoxy polymer or precursor, to form a cured, crosslinked epoxy coating. Such a crosslinker will typically be a chemical compound bearing at least three functional groups, preferably the same group, which will react with the epoxy polymer or precursor in the presence of an acid catalyst to generate a covalent bond. Preferred amine crosslinkers include melamine formaldehydes and aziridines. Suitable crosslinkers include trimethylolpropane tris[3-(2-methylaziridinyl)propanoate, which is sold under the trade names Ionac PFAZ 322 available commercially from Cybron Chemical, Inc. of Birmingham, N.J. and NeoCryl CX-100 available commercially from Zeneca Resins of Wilmington, Mass. Another effective crosslinker is the polymer generated by reaction of 1,3,5-triazine-2,4,6-triamine with formaldehyde, sold commercially as Cymel 350 or Cymel 385 available commercially from Cytec of West Paterson, N.J. The most preferred amine crosslinker is Resimene 797, a melamine crosslinker which is commercially available from Solutia. A useful preferred aziridine crosslinker is Hydroflex XR-2990 which is commercially available from H.B. Fuller Company of St. Paul, Minn. The weight percentage of the crosslinker in the uncured epoxy coating ranges from at about 20% to about 60%, preferably from about 30% to about 45%, more preferably from about 35% to about 40% based on the weight of the epoxy coating composition solids.
The acid cat
Altizer Lance R.
Chung Insuk
Gibboni David J.
Shah Jayesh C.
Copenheaver Blaine
Criss Roger H.
Honeywell International , Inc.
Paulraj Christopher
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