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
1999-08-30
2001-02-27
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...
C524S430000, C524S779000, C524S783000, C524S786000
Reexamination Certificate
active
06194507
ABSTRACT:
FIELD OF INVENTION
The present invention concerns a color concentrate for use in coloring plastics. More particularly, the present invention concerns a metal containing thermoplastic color concentrate (masterbatch) for use in imparting a metallic effect or appearance to the thermoplastic polymer that is being colored.
BACKGROUND
Thermoplastic polymers are often colored in the molten state by the addition of color concentrates. Color concentrates are highly loaded dispersed colorants in a carrier polymer. The carrier polymer being either the same chemistry, with higher melt flow characteristics as or compatible with the polymer to be colored. Color concentrates are generally used to ensure good dispersibility and incorporation of pigments and other additives. Use of color concentrates can also create a much cleaner environment for an end user who does not have to involve oneself with dusty colorants and other hard to handle materials.
There are several methods for adding a color concentrate to a thermoplastic polymer that is to be colored. However, the most common method utilized today involves the controlled metering of the color concentrate into the throat of a polymer extruder or injection molding machine using pellet feeders. In this application, the concentrate is supplied in a pellet form.
Color concentrates containing metal particles are known in the prior art. Such concentrates are utilized to impart a metallic look or effect to polymers. However, to date, the use of such concentrates has presented a variety of problems including poor incorporation or distribution of the metal within the polymer, low metal loading levels that fail to produce a meaningful metallic effect in the polymer being colored and the formation of knit lines, flow lines, diration lines and other molding marks upon use of the colored polymer. Moreover, such concentrates have commonly been made using a wax carrier, and waxes at higher concentrations are undesirable in many applications. The present invention affords a metal filled color concentrate that overcomes these deficiencies.
SUMMARY OF INVENTION
The present invention provides a new and improved metal containing color concentrate that affords a variety of advantages including a high metal content, good metal distribution and pigment dispersibility and distribution, minimal adverse influence on the physical properties of the polymer being colored and good molding characteristics. The concentrate of the present invention is used to produce a flat or brushed metallic appearance in the polymer that is being colored.
The color concentrate of the present invention comprises from about 10% to about 30% by weight metal particles component, from about 1% to about 15% by weight colorant material (pigment), and from about 60% to about 90% by weight thermoplastic polymer. The metal particles component comprises a bimodal distribution of particles that exhibit both a lenticular and a spherical distribution. The metal particles component comprises from about 70 to about 95 percent by weight lenticular shape aluminum particles having an average particle size of from about 20 to about 75 &mgr;m, and from about 5 to about 25 percent by weight spherical shape aluminum particles having an average particle size of from about 20 to about 75 &mgr;m. The color concentrates of the present invention include less than about 5% by weight wax, and preferably the concentrate will have a melt flow similar to that of the thermoplastic polymer being colored.
These and other aspects of the present invention will become clear to those skilled in the art upon the reading and understanding of the specification and the claims below.
DETAILED DESCRIPTION
Color concentrates made in accordance with the present invention yield various advantages. These advantages include: (I) the production of a concentrate that provides good dispersion and distribution when added to the thermoplastic polymer being colored; (ii) the production of colored thermoplastic polymer that displays a significant metallic look or effect that produces a matte or brushed appearance in high light conditions (e.g., outdoors in full or almost full sunlight); and (iii) the absence ofknit lines, flow lines and diration lines upon molding of the colored thermoplastic polymer. The formation of knit lines is avoided because the metal particles do not pile up into a vertical orientation during molding. Additionally, knit lines are avoided because there is no agglomeration of metal particles within the thermoplastic polymer and the melt flow of the concentrate is controlled very close to the melt flow of the thermoplastic polymer that is being molded, and the concentrate is capable of providing a metal content in the polymer being colored of 1-2% by weight.
Color concentrates made in accordance with the present invention may utilize a variety of different thermoplastic carrier polymers or mixtures of such polymers. Waxes are not used as the carrier in concentrates of the present invention. Thus, the color concentrates of the present invention comprise less than 5% by weight wax. The thermoplastic carrier polymer may comprise an amorphous or crystalline material selected from the group consisting of a styrenic polymer, a vinyl halide polymer, polyamides and an olefinic polymer. The styrenic polymers include, for example, polystyrene, high impact polystyrene (HIPS), styrene/acrylonitrile copolymers (SAN), copolymers of acrylonitrile/butadiene/styrene (ABS) and substituted styrenes such as a-methyl styrene, methyl methacrylate, polysulphones and copolysulphones, polyphenylene oxides (PPO), polycarbonates, polymers and copolymers ofacetals, and thermoplastic polyurethanes. Polyamide polymers include, for example, Nylon 6, Nylon 6,6 and Nylon 6,12 and glass filled versions thereof. Vinyl halide polymers include, for example, poly(vinyl chloride) (PVC).
The olefinic polymers include, for example, polymers and copolymers of a-olefins such as polyethylene, polypropylene, polybutene, poly-4-methyl pentene-1, propylene/ethylene copolymers and copolymers of 4-methyl pentene-1 with linear a-olefins containing 4 to 18 carbon atoms.
Preferably, whatever polymer system is utilized, it is best if a significant portion of the polymer is supplied in powder form to ensure proper mixing. Use of a blend of powder and pellets helps to prevent the settling of the metal particles during mixing. Preferably, the powder accounts for from about 30% to about 70% by weight of the thermoplastic carrier. Also, preferably, whatever polymer system is used as the carrier, the color concentrate should have the same or a similar melt flow to the polymer that is to be colored.
The metal particles component of the present invention comprises a bimodal distribution of aluminum particles having both a spherical and a lenticular configuration. This bimodal particle size distribution has been found to be critical relative to the formation of a product with a matte metal effect. The metal particles component comprises from about 70 to about 95 percent by weight lenticular shape aluminum particles having an average particle size of from about 20 to about 75 &mgr;m, and from about 5 to about 25 percent by weight spherical shape aluminum particles having an average particle size of from about 20 to about 75 &mgr;m. Metal particles suitable for use in the present invention may be purchased from the Silberline Manufacturing Company, Inc. of Tamaqua, Pa.
The colorant material may comprise any one or more of a number of commercially available colors or pigments so as to provide the described color effect in the concentrate and the thermoplastic polymer that is to be colored. As used in this specification and claims below “colorant material” means any conventional inorganic or organic pigment or organic dyestuff. Such materials are described, for example, in
Kirk
-
Othmer Encyclopedia of Chemical Technology,
Third Edition, Vol. 6, pp. 597-617, which is incorporated herein by reference. Examples of inorganic pigments include, for example, titanium dioxide, iron oxide, zi
Cain Edward J.
Ferro Corporation
Rankin, Hill Porter & Clark LLP
Wyrozebski Katarzyna
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