Coating processes – Particles – flakes – or granules coated or encapsulated – Solid encapsulation process utilizing an emulsion or...
Reexamination Certificate
1999-06-03
2003-01-07
Pianalto, Bernard (Department: 1762)
Coating processes
Particles, flakes, or granules coated or encapsulated
Solid encapsulation process utilizing an emulsion or...
C427S213300, C427S213310, C427S213320, C427S213340, C427S213350, C427S213360
Reexamination Certificate
active
06503559
ABSTRACT:
TECHNICAL FIELD
The present invention relates to colorant compositions containing neonanoplasts. The colorant compositions exhibit improved color brightness and brilliance due to the incorporation of one or more colorants in the neonanoplasts. The colorant compositions may be printed onto virtually any substrate. The colorant compositions of the present invention have particular utility in the area of printed textiles.
BACKGROUND OF THE INVENTION
A major problem with colorants is that they tend to fade when exposed to electromagnetic radiation such as sunlight or artificial light and the like. It is believed that most of the fading of colorants when exposed to light is due to photodegradation mechanisms. These degradation mechanisms include oxidation or reduction of the colorants depending upon the environmental conditions in which the colorant is placed. Fading of a colorant also depends upon the substrate upon which they reside.
Product analysis of stable photoproducts and intermediates has revealed several important modes of photodecomposition. These include electron ejection from the colorant, reaction with ground-state or excited singlet state oxygen, cleavage of the central carbon-phenyl ring bonds to form amino substituted benzophenones, such as triphenylmethane dyes, reduction to form the colorless leuco dyes and electron or hydrogen atom abstraction to form radical intermediates.
Various factors such as temperature, humidity, gaseous reactants, including O
2
, O
3
, SO
2
, and NO
2
, and water soluble, nonvolatile photodegradation products have been shown to influence fading of colorants. The factors that effect colorant fading appear to exhibit a certain amount of interdependence. It is due to this complex behavior that observations for the fading of a particular colorant on a particular substrate cannot be applied to colorants and substrates in general.
Under conditions of constant temperature it has been observed that an increase in the relative humidity of the atmosphere increases the fading of a colorant for a variety of colorant-substrate systems (e.g., McLaren, K.,
J. Soc. Dyers Colour
, 1956, 72, 527). For example, as the relative humidity of the atmosphere increases, a fiber may swell because the moisture content of the fiber increases. This aids diffusion of gaseous reactants through the substrate structure.
The ability of a light source to cause photochemical change in a colorant is also dependent upon the spectral distribution of the light source, in particular the proportion of radiation of wavelengths most effective in causing a change in the colorant and the quantum yield of colorant degradation as a function of wavelength. On the basis of photochemical principles, it would be expected that light of higher energy (short wavelengths) would be more effective at causing fading than light of lower energy (long wavelengths). Studies have revealed that this is not always the case. Over 100 colorants of different classes were studied and found that generally the most unstable were faded more efficiently by visible light while those of higher lightfastness were degraded mainly by ultraviolet light (McLaren, K.,
J. Soc. Dyers Colour
, 1956, 72, 86).
The influence of a substrate on colorant stability can be extremely important. Colorant fading may be retarded or promoted by a chemical group within the substrate. Such a group can be a ground-state species or an excited-state species. The porosity of the substrate is also an important factor in colorant stability. A high porosity can promote fading of a colorant by facilitating penetration of moisture and gaseous reactants into the substrate. A substrate may also act as a protective agent by screening the colorant from light of wavelengths capable of causing degradation.
The purity of the substrate is also an important consideration whenever the photochemistry of dyed technical polymers is considered. For example, technical-grade cotton, viscose rayon, polyethylene, polypropylene, and polyisoprene are known to contain carbonyl group impurities. These impurities absorb light of wavelengths greater than 300 nm, which are present in sunlight, and so, excitation of these impurities may lead to reactive species capable of causing colorant fading (van Beek, H. C. A.,
Col. Res. Appl
., 1983, 8(3), 176).
Mother nature protects naturally-occurring colorants from one or more of the above-described photodegradation mechanisms by surrounding the naturally-occurring colorants with a cell wall. The cell wall prevents destructive materials, such as O
2
gas, from reaching the colorant. The result is a colorant, which maintains its brilliance, brightness and beauty even when exposed to sunlight day after day.
What is needed in the art is a colorant system, which provides protection to a colorant in much the same way that nature protects colorants. There exists a need for methods and compositions, which are capable of stabilizing a wide variety of colorants, regardless of the stability of the colorant, from the effects of both sunlight and artificial light.
SUMMARY OF THE INVENTION
The present invention addresses the needs described above by providing compositions and methods for stabilizing colorants against radiation including radiation in the visible wavelength range. The present invention provides a system for shielding a colorant from destructive forces, such as oxidants and reductants. By providing a protective shield for the colorant, very unstable colorful dyes may be used in a wide variety of printing applications, which were believed to be impossible applications due to rapid degradation of the dye.
The present invention is directed to neonanoplasts formed by microemulsion technology. The neonanoplasts contain one or more colorants and optionally colorant stabilizers. The neonanoplasts comprise a polymeric membrane, which prevents degradable materials from reaching the colorant. The neonanoplasts may be incorporated into a variety of liquid mediums to form colorant compositions.
The present invention is further directed to a method of stabilizing a colorant by encapsulating the colorant in a polymeric membrane, forming a neonanoplast. In one embodiment of the present invention, one or more colorant stabilizers are also encapsulated in the polymeric membrane, creating multiple levels of colorant protection from photodegradable mechanisms.
The present invention is also directed to colorant compositions containing the above-described neonanoplasts. The colorant compositions may be applied to any substrate to impart a color to the substrate. In one embodiment of the present invention, a colorant composition comprising neonanoplasts, a liquid medium and a pre-polymer is coated onto a substrate and subsequently exposed to radiation to fix the neonanoplast to the substrate via the polymerization of the pre-polymer.
In another embodiment of the present invention, neonanoplasts are present in a polymer coating of a heat transfer product, such as is used for transferring graphic images onto clothing.
The neonanoplasts are particularly effective in ink jet inks. Use of the neonanoplasts, as described herein, intensifies the colors and stabilizes the colorants when exposed to light and other potentially degrading conditions. Additionally, the neonanoplasts are particularly effective in coatings for paper products and textiles.
These and other features and advantages of the present invention will become apparent after a review of the following detailed description of the disclosed embodiments and the appended claims.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is directed to neonanoplasts formed by microemulsion technology. Neonanoplasts are spherically-shaped polymeric membranes which encapsulates a colorant, and optionally other materials, to prevent degradable materials from reaching the colorant. Neonanoplasts can be formed by a microemulsion process. Neonanoplasts may have an average particle size of less than about 1000 nanometers (nm), desirably less than 500 nm. The neonanoplasts may be incorporated into a
MacDonald John Gavin
Nohr Ronald Sinclair
Kilpatrick & Stockton LLP
Kimberly--Clark Worldwide, Inc.
Pianalto Bernard
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