Plastic and nonmetallic article shaping or treating: processes – Random variegated coloring during molding – By compression in a closed mold cavity
Reexamination Certificate
2001-07-27
2004-03-09
Lee, Edmund H. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Random variegated coloring during molding
By compression in a closed mold cavity
C264S108000, C264S110000, C264S118000, C264S119000, C264S152000, C264S247000, C264S248000, C264S320000
Reexamination Certificate
active
06702967
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to molding formulations that are fabricated into decorative surface materials, which have unique decorative patterns.
2. Description of the Related Art
Solid surface materials are essentially non-porous composites of finely divided mineral fillers dispersed in an organic polymer matrix. Examples of commonly used fillers include alumina trihydrate, calcium carbonate, silica, and alumina. Examples of commonly used thermoset polymeric materials include acrylic, polyester, melamine, urethane, acrylo-urethane, epoxy resins and combinations thereof. Most solid surface materials are manufactured by thermoset processing, such as sheet casting, cell casting, injection molding, or bulk molding. The decorative qualities of such products are greatly enhanced by incorporating pigments and colored particles such that the composite resembles natural stone. The range of patterns commercially available is constrained by the intermediates and processes currently used in the fabrication of such materials.
Solid surface materials in their various applications serve both functional and decorative purposes. Since incorporating various attractive and/or unique decorative patterns enhances their utility, such patterns constitute intrinsically useful properties, which differentiate one product from another. The same principle applies to naturally occurring materials such as wood or stone whose utility, for example in furniture construction, is enhanced by certain naturally occurring patterns, e.g., grain, color variations, veins, strata, inclusions, and others. Commercially manufactured solid surface materials often incorporate decorative patterns intended to imitate or resemble the naturally occurring patterns in granite or marble. However, due to limitations of feasibility and/or practicality, certain decorative patterns and/or categories of decorative patterns have not previously been incorporated in solid surface materials.
Decorative patterns have been previously achieved in traditional thermoset fabrication primarily by the following three methods:
(i) Monochromatic or polychromatic pieces of a pre-existing solid surface product are mechanically ground to produce irregularly shaped colored particles, which are then combined with other ingredients in a new thermoset formulation. Curing the reaction combination during casting or molding produces a solid surface material in which colored inclusions of irregular shapes and sizes are surrounded by, and embedded in a continuous matrix of different color.
(ii) During casting of a thermoset reaction combination, a second reaction combination of a different color is added in such a way that the two only intermix to a limited degree. In the resulting solid surface material, the different colored domains have smooth shapes and are separated by regions with continuous color variation.
(iii) Different colored solid surface products are cut or machined into various shapes, which are then joined by means of adhesive to create multi-colored inlayed patterns or designs.
Using these traditional thermoset methods it is not possible to produce certain categories of decorative patterns, which occur in natural stone.
Moreover, the inclusions incorporated in solid surface products produce; by method (i) are limited to sizes less than about 20 mm, more generally less than 5 mm, and must constitute less than about 80% of the thermoset reaction mix, more generally less than 20%.
SUMMARY OF THE INVENTION
This invention is directed to decorative surface materials having unique decorative patterns and categories of patterns not previously represented. The present invention comprises a decorative pattern in which a multiplicity of domains derived from thermoset molding of fragments of thermosettable molding formulations exhibiting different shading at the domain interfaces provided by different orientations of orientable anisotropic aesthetic-enhancement particles within the domains. As used herein, a domain comprises visibly distinct regions within the final product that correspond to the original individual charge fragments. In addition, further, more significant, changes in shading occur at interfaces, i.e. knit regions, between the domains due to flow orientation of the aesthetic-enhancement particles during processing or concentration gradients of the aesthetic-enhancement particles in other regions of the domain. The changes in appearance due to concentration gradients may occur in conjunction or independently of the presence of aesthetic-enhancement particles.
Incorporation of orientable anisotropic aesthetic-enhancement particles into the formulation allows the creation of additional aesthetics. By anisotropic it is meant having different physical properties in different directions, e.g. having an appearance that varies depending on the angle of observation. The particles should have an aspect ratio of at least 3. It will be apparent that the patterns in the decorative surface materials of this invention are three dimensional and distinct from patterns obtained by applying decals, appliques and paint to a surface. These particles have an aspect ratio that is high enough that the particles tend to become aligned with material flow directions when processed. The aspect ratio is the length of a particle divided by its diameter, or stated differently, its largest dimension divided by its smallest dimension. These particles also have a different aesthetic effect when aligned at various angles relative to the material surface and to the viewer. These effects may be due to angle dependent reflectivity, angle dependent color absorption/reflection, or visible shape. Examples of these aesthetic-enhancement particles include, but are not limited to minerals (mica, alumina, silica, etc.), glasses, ceramics, polymers or other natural or synthetic substrates coated with various materials (minerals, dyes, etc.) for reflectivity, interference patterns or selective color absorption. Fibers, films, and ribbons also present a different appearance depending on the angle of observation.
These anisotropic particles tend to orient during the processing of the molding formulation. The degree of orientation will depend on the methods of mixing and further processing. During mixing, the particles will tend to orient on a localized basis (providing the optical effect), but the over all orientation in the bulk of the material will be somewhat chaotic due to the complicated flow patterns during mixing. Additional processing, such as extrusion, may further align the particles on both a local and overall basis. When the formulation is chopped, ground, extruded, or by some other means fragmented into smaller masses (i.e. charge fragments) this orientation is retained. When these charge fragments are arranged either by a random or selective process in a mold and pressed, some of the anisotropic particles retain their original orientation, while some are reoriented by material flow in the mold. The degree of reorientation depends on the amount of flow experienced by that particle. This creates an aesthetic where the individual charge fragments all vary slightly in appearance due to the different general orientation of the anisotropic aesthetic-enhancement particles relative to the surface of the material and to the observer. In areas of greater flow, particularly in the area between charge fragments where the fragments contact each other and there is a change in the predominate direction of material flow, this effect is more pronounced, creating a more visible change in appearance.
Another method of enhancing the appearance is by incorporating more than one flowable thermosettable molding formulation, either as a partial blend or a mixture of molding formulations. The two formulations can have complimentary or contrasting aesthetics, depending on the desired effect. In the final product each domain will have shade variations and knit regions due to flow and aesthetic particle orientation, with the additional contrast of the
Overholt Allan R.
Paplham William P.
Weberg Rolf T.
E. I. du Pont de Nemours and Company
Lee Edmund H.
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