Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
1999-10-21
2002-10-29
Cain, Edward J. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S765000, C524S770000, C524S783000, C524S786000, C524S787000
Reexamination Certificate
active
06472467
ABSTRACT:
The present invention relates generally to the art of hard coatings. More specifically, the present invention relates to novel hard coatings produced from novel storage-stable solutions containing two different inorganic components plus a third component, which contains cross-linkable organic functionality.
BACKGROUND OF THE INVENTION
For purposes of the present specification, a hard coating will refer to a coating that exhibits good mechanical properties, such as scratch-resistance and abrasion-resistance. There are many different approaches known in the art for producing hard coatings. These hard coatings are utilized in many different applications. For example, hard coatings are often used to protect furniture, as well as to protect various parts of an automobile.
It is known in the art to produce hard coatings using sol-gel processes and techniques. It is also known that the formation of dense, pure inorganic coatings by the sol-gel route requires heating. The amount of heat necessary to produce dense, pure inorganic coatings makes it prohibitive to coat certain materials, such as plastic substrates. Additionally, pure inorganic coatings are brittle due to their high (three-dimensional) inorganic network connectivity.
The introduction of organic components to sol-gel compositions can lead to a reduction of overall inorganic network connectivity in coatings and allow coatings to be produced at lower temperatures. Also, the inclusion of organic components allows coatings to be more flexible viscoelastic (that is, less brittle) while maintaining good scratch resistance and abrasion resistance. Some of these inorganic/organic coatings have become known as ormosils (organically modified silicates), ormocer (organically modified ceramics), or nanomers (nanoparticle and organic component containing polymer type materials).
However, up to now these inorganic/organic coatings have suffered from a number of deficiencies. First, it has been extremely difficult, if not impossible in some cases, to produce coatings having an inorganic portion greater than about 40 percent. Coatings having less inorganic content will have insufficient abrasion resistance or insufficient scratch resistance for many applications. Second, the inorganic/organic coating compositions of the prior art are either sensitive to water or immiscible in water, requiring organic solvents that may be expensive, difficult, or even hazardous to use.
Accordingly, there exists a need in the industry for hard coatings that can be easily and economically produced at low temperatures. The present invention addresses these concerns.
SUMMARY OF THE INVENTION
In one aspect, the present invention is a storage-stable solution that can be easily utilized to produce hard coatings. Solutions of the present invention comprise a) a solvent; b) inorganic particles dispersed substantially uniformly in the solution, said particles having a size of from about 1 nanometer to about 100 nanometers; c) an inorganic surface modifier dispersed substantially uniformly in the solution, the weight percent of said modifier comprising from about 1 percent to about 30 percent of the total weight of b) and c); and d) an organic cross-linker dispersed substantially uniformly in the solution; wherein b) and c) together constitute from about 30 weight percent to about 70 weight percent of b), c), and d).
In one preferred embodiment, solutions of the present invention are aqueous. Although other solvents may be used in solutions of the present invention to produce coatings of the present invention, an important advantage of the present invention is that solutions of the present invention can be produced using only water as a solvent.
The components in solutions of the present invention can be mixed in a variety of ways known in the art. A preferred method for mixing the components is to first prepare a solution containing the inorganic surface modifier in the solvent and then add the organic cross-linker, or a solution containing the cross-linker, to the solution containing the surface modifier. Next, this solution containing the inorganic surface modifier and the organic cross-linker is added to a sol containing the inorganic particles.
The method of producing coatings from solutions of the present invention is not particularly critical. The solution is first applied to a substrate to be coated and then the solution is cured to produce the coating. Solutions of the present invention are cured in one of two ways depending on whether the solvent present needs to be removed or whether the solvent is a reactable solvent. The first method of curing is to first remove the solvent and then apply appropriate stimulus (for example, heat or UV light) to cross-link or polymerize the organic cross-linker. The second method of curing solutions of the present invention, used when a reactable solvent is present, is to react the solvent, instead of removing it, and cross-link or polymerize the organic cross-linker by applying appropriate stimulus.
A preferred method for curing solutions of the present invention, especially aqueous solutions, is to apply sufficient heat to the solution to remove the solvent and promote the cross-linking. Generally, solutions of the present invention can be cured at a temperature that is sufficiently low to allow solutions of the present invention to be cured on plastic substrates, such as substrates made of polycarbonate, PET, PEN, PVC, PMMA, polyolefins, polysulfone, and polyurethane.
In yet another aspect, the present invention is a novel composition that can be utilized as an abrasion-resistant coating. Compositions of the present invention comprise a) inorganic particles dispersed substantially uniformly throughout the composition, said particles having a size of from about 1 nanometer to about 100 nanometers, said inorganic particles comprising from about 30 volume percent to about 70 volume percent of the composition volume; b) inorganic modifier particulates dispersed substantially uniformly throughout the composition, said modifier particulates having a size ratio relative to the size of said inorganic particles of from about 1:50 to about 1:2, said modifier particulates comprising from about 1 volume percent to about 20 volume percent of the composition volume); and c) a cross-linked organic component comprising from about 10 volume percent to about 70 volume percent of the composition volume.
DETAILED DESCRIPTION OF THE INVENTION
Solutions and coatings of the present invention contain at least two different inorganic components and at least a third component, which contains cross-linkable organic functionality. For purposes of this specification, this third component will be referred to as an organic cross-linker. The cross-linker may not be entirely organic, but is at least partially organic in nature. Thus, solutions and coatings of the present invention may be considered dual-phase in the sense that they contain both inorganic components (that is, an inorganic phase) and an organic component (that is, an organic phase). Coatings of the present invention may be considered bimodal in the sense that the two inorganic components are of differing size. In addition to the inorganic components and the organic cross-linker, solutions of the present invention also comprise a solvent.
Solutions of the present invention are storage-stable. By storage-stable, it is meant that solutions of the present invention can be put in storage for periods of days or even months and then utilized without additional preparation (such as remixing).
There are two types of solvents that are useful in solutions of the present invention. The first type of solvent acts as a carrier medium for the other solution components and must be removed from solutions of the present invention during the process of producing a coating from these solutions. Solvents of the first type that are useful in solutions of the present invention include water, organic solvents, and mixtures thereof. Preferred solvents are water, alcohols, ketones, glycol ethers, glycol esters,
Cain Edward J.
Dow Global Technologies Inc.
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