Composition and Process for Making Gold Colored Olefin Polymers

This invention relates to pigmented olefin polymer compositions.

Conventional color pigments and dyes can be added to polyolefins to produce a variety of pigmented polyoefins. Pigmented polyolefins are aesthetically pleasing, and thus, the resultant colored polyolefin product is more appealing and/or marketable to a consumer. However, pigmented polyolefins are not available in all colors. Metallic colored polyolefins, with a consistent pigment distribution, are difficult to make. The pigments usually used to produce metallic colored polyolefins are metallic based pigments. The metallic based pigments is difficult to evenly distribute in the polyolefin and the resultant molded product frequency is not uniform in color.

Molded polyolefin products, both pigmented and unpigmented, can be produced in grit blasted molds or in polished molds. Polished molds are more difficult and more expensive to produce, because the interior mold surface must be smoothed or polished prior to use. If a polished mold needs to be cleaned during molding operations, the interior of the molds should be inspected for scratches and, if necessary, re-polished. Hence, polished molds are not as easy to use and maintain as grit blasted molds. Additionally, imperfections and blemishes in the final product, which can be caused, for example, by air entrapment are much more obvious in products produced in a polished mold. Metallic colored polyolefins can be molded in a grit blasted mold; however, a glossy, reflective finish is more difficult to obtain in a grit blasted mold.

It is thus an object of this invention to provide a metallic colored polyolefin.

It is a further object of this invention to produce a metallic gold colored polyolefin.

It is another object of this invention to produce a metallic Fort Knox gold colored polyolefin.

It is yet a further object of this invention to produce a metallic colored polyolefin product with a glossy finish.

It is yet a further object of this invention to produce a metallic colored polyolefin product with a glossy finish in a grit blasted mold.

In accordance with this invention, it has been discovered that the following compounds, when added in the appropriate concentrations, provide a metallic gold colored polyolefin composition:

(a) olefin polymer,

(b) mica-based gold pigment,

(c) mica-based bronze pigment,

(d) carbon black, and

(e) optionally, yellow pigment.

In accordance with another embodiment of this invention, a blend of one or more olefin polymers with a plurality of mica-based pigments, carbon black, and optionally, yellow pigment, is blended, extruded, and finally, molded in a grit blasted mold under conditions sufficient to produce a container having a glossy, metallic, gold color.

The present invention provides a composition and a process to prepare a metallic, glossy, gold colored olefin polymer object in a grit blasted mold. More specifically, the metallic, glossy, gold colored olefin polymer object is a metallic, glossy, Fort Knox gold colored polyolefin product.

The metallic, gold colored olefin polymer comprises combining pigments with an olefin polymer. At least three pigments, a mica-based gold pigment, a mica-based bronze pigment, and carbon black, are combined with the olefin polymer; a fourth pigment, a yellow pigment, optionally, can be added. Broad, intermediate, and preferred ranges of the olefin polymer and of four pigments in the final gold colored product are listed in the following table. The ranges are listed in approximate weight percents of each component in the final composition. The broad ranges were selected in order to obtain the desired coloration results; the preferred ranges are preferred because they define a composition possessing the desired physical and chemical properties best suited to blend, extrude, and/or mold a metallic, glossy, gold colored polyolefin product. Too much mica-based gold pigment results in a product that is too yellow in color; too little mica-based gold pigment creates a bronze colored product. An excess of mica-based bronze pigments produces a product that is too orange and too little mica-based bronze pigment results in a yellow colored product. Too much carbon black creates a dark gold, almost green, product; too little carbon black produces a product too light in gold color. An excess of yellow pigment results in a product that is too yellow in color.

As shown in Table I, the final metallic, glossy, gold colored olefin polymer comprises pigment in the range of about 0.5 to about 3 weight percent, based on the weight of the final colored polyolefin. The total amount of pigment in the final product, as given above, is defined as the pigment load or pigment loading factor.

The four pigments useful in accordance with this invention to produce a metallic, gold colored olefin polymer composition are commercially available products. The following tabulation gives possible suppliers and the trademarks for each of the pigment compounds.

The pigment suppliers and trademarks listed in Table II are merely examples of the pigments useful in this invention; the invention is not restricted only to those pigments shown in Table II. As shown in Table II, the gold and bronze pigments are best described as anatase titanium oxide (TiO.sub.2) and/or iron oxide (Fe.sub.2 O.sub.3 or Fe.sub.3 O.sub.4) coated mica, with a particle size of less than about 200 microns. The pigment mica substrate can be described as platelet-shaped, transparent particles, which can include, for example, talc platelets; glass platelets; and various forms of mica, such as, for example, muscovite, white, biotite, phlogopite, related vermiculite, and synthetic micas. The carbon black is best described by the ASTM designation N110, according to ASTM method number D1765-87a; however, other types of carbon black, such as any N100 series, N200 series, N300 series, and mixtures thereof, according to ASTM method number D1765-87a, can also be used. The yellow pigment can be any type of translucent yellow pigment that can blend with a polyolefin.

The metallic, gold colored olefin polymer composition can be prepared directly as a final product with the appropriate weight percent amounts of each component, as earlier shown. However, it is also possible to produce a polymer concentrate blend, which is a metallic, gold colored olefin polymer with more concentrated pigment quantities. This metallic, gold colored olefin polymer concentrate blend can then be combined with an appropriate amount of additional colored or uncolored olefin polymer to produce a metallic, gold colored olefin polymer with a pigment load in the final product in the range of about 0.5 to about 3 weight percent.

The olefin polymer useful in this invention can be any olefin homopolymer or copolymer with a density of greater than about 0.94 g/cc. Exemplary polyolefins include, but are not limited to, polyethylene, polypropylene and mixtures thereof. The polyethylene component of the invention can be produced by any method known in the art. One method of polyethylene production uses a silica-supported chromium-oxide catalyst system, such as described in U.S. Pat. No. 2,825,721 and U.S. Pat. No. 2,951,816 by Hogan and Banks, which are herein incorporated by reference. Another method of polyethylene production uses a transition metal catalyst and relatively low temperatures and relatively low pressures.

Polyethylene also can be produced by copolymerizing ethylene with one or more higher alpha-olefin comonomers, preferably, with an alpha-olefin having about 3 to about 8 carbon atoms. The comonomer is normally present in small percentage, i.e., an amount to maintain a polymer density of greater than about 0.94 g/cc. Usually, up to about 5 mole percent comonomer is present in the total monomer mixture. Examples of ethylene comonomers include, but are not limited to propylene, 1-butene, 1-hexene, and mixtures thereof. 1-hexene, which produces butyl branches, is the presently preferred comonomer. Marlex.RTM. HHM 5502 ethylene-hexene copolymer is the preferred polyolefin component of the invention. Marlex.RTM. resins are available from Phillips Chemical Company of Bartlesville, Okla.

The polypropylene component of the invention can be any crystalline polypropylene, such as described in U.S. Pat. No. 4,376,851 by Hogan and Banks, which is herein incorporated by reference. The polypropylene component can be produced by any method known in the art.

The metallic, gold tinted olefin polymer composition can be processed to form a glossy, metallic, gold product by sufficiently mixing the necessary components and then extruding the composition into pellets for future use or into a parison for blow molding. The operating, or processing, parameters for the blending and extruding processes affect the appearance, such as, for example, the gloss, texture, tint and hue, of the final metallic, glossy, gold product. The processing parameters especially affect the gloss of the final product. Gloss, defined in terms of this invention, refers to the reflective properties of the surface of the tinted olefin polymer product; gloss does not necessarily imply smoothness or color. When dealing with the composition of this invention, too much rough handling of the olefin and pigments in the form of, such as, for example, shear, grinding, and kneeding, results in a loss of gloss in the final product. The olefin polymer and the pigments are dry blended in any type of dry blender, mixer, or tumbler. The blending process produces a dry blended product which is a fairly evenly dispersed mixture of the olefin polymer and pigments. The speed of the blender should be in the range of about 700 to about 1000 rotations per minute (rpm). Preferably, the blender speed is in the range of about 750 to about 900 rpm. Operating the blender at a higher rpm can cause a decrease in the gloss of the final product; too low of a blender speed does not always adequately mix the dry blend.

The dry blended product can then be extruded into pellets for future use or into parison for blow molding. The maximum screw speed of the extruder is about 80 rpm. Preferably, the extruder screw speed is less than about 70 rpm. An excessively fast extruder screw speed results in a decrease of the gloss of the final olefin polymer product.

The opening or openings of the extruder have a size of greater than about 0.25 millimeters (mm). An opening of less than about 0.25 mm decreases the gloss of the final product.

The operating temperature of the extruder is any temperature appropriate to extrude olefin polymers. The temperature can vary with different olefin polymers. For example, with high density polyethylene, temperatures in the range of about 190.degree. to about 235.degree. C. are appropriate.

A further understanding of the present invention and its advantages is provided by reference to the following examples.

A pigment concentrate blend in pellet form was made by dry blending the following components in a Henschel mixer at slow speed (about 700 rpm);

This dry blend of components was then fed to a 11/2 inch Johnson compound extruder, run at a screw speed of 80 rpm, a melt zone temperature (zone 0) of 415.degree. F., a feed zone temperature (zone 1) of 420.degree. F., transition zone temperature (zone 2) of 410.degree. F., a metering zone temperature (zone 3) of 410.degree. F., a die zone temperature (zone 4) of 410.degree. F., and 300 psi pressure at the die inlet which is due to the placement of 20 mesh, 40 mesh, and 60 mesh screens prior to the die (the 20 and 40 mesh screens are used only for support of the 60 mesh screen). The strands from the Johnson compound extruder were then directed through a water bath and a rotating blade Cumberland model size 6, pelletizer to produce gold polyethylene pellets.

In a separate run the following ingredients were dry blended in the same Henschel mixer, or tumbler, as in Example 1, at slow speed; this is identified as full component blend:

This dry blend of components was then fed to the same 11/2 inch Johnson compound extruder as in Example 1, run at a screw speed of 70 rpm, a melt zone temperature (zone 0) of 405.degree. F., a feed zone temperature (zone 1) of 460.degree. F., transition zone temperature (zone 2) of 450.degree. F., a metering zone temperature (zone 3) of 450.degree. F., a die zone temperature (zone 4) of 450.degree. F., and 500 psi pressure at the die inlet. The strands from the Johnson compound extruder were then directed through a water bath and a rotating blade, Cumberland model size 6, pelletizer to produce gold pellets.

The concentrate blend, with additional HDPE in a 5 to 1 letdown ratio (such as 5 pounds HDPE with 1 pound concentrate), and the full blend composition, in separate runs were fed to a Kautec model KEB 1 continuous blow mold extruder, run at 65 rpm, zone 0 temperature 402.degree. F., zone 1 temperature 380.degree. F., zone 2 temperature 390.degree. F., zone 3 temperature 410.degree. F., and a die face pressure of 900 psi (no screens were in front of the die). The extruder was connected to a quart oil can split grit blasted mold maintained at a temperature of 60.degree. F. and a blow pressure of 2.25 bars (225 psi). This resulted in a glossy, metallic, Fort Knox gold pigment container having a 2% bottle pigment load. (Percent pigment load means the percent of pigment in the total final resin volume found in the bottle).

The examples have been provided merely to illustrate the practice of the invention and should not be read so as to limit the scope of the invention or appended claims in any way. Reasonable variations and modifications, not departing from the essence and sprit of the invention, are contemplated to be within the scope of patent protection desired and sought.