Patent Publication Number: US-2011060061-A1

Title: Masterbatch composition having a high polymer processing aid

Description:
FIELD OF THE INVENTION 
     The present invention relates in general to masterbatch compositions having a colorant, a processing aid, and optionally one or more additives, and a process for making the same. 
     BACKGROUND OF THE INVENTION 
     Colorants such as pigment preparations are often produced for masterbatches. A masterbatch is a granular, dust-free concentrate of a plastomeric or elastomeric polymer comprising a fraction of a colorant. Masterbatches are used to color plastics, being added to the plastic to be colored prior to or during processing. Masterbatches are used because they provide better colorant dispersion than neat colorant. 
     A variety of processes for producing masterbatches are known and the following processes are standard in the production of the masterbatches: a) the mixing of a suitable matrix (polymers) with the colorant; b) extrusion and kneading with subsequent grinding of the colorant concentrate; or c) extrusion and subsequent fine spraying, hot chopping, or strand pelletizing. 
     Known masterbatches generally include a colorant, a dispersant, a thermoplastic polymer, and optionally one or more additives. The thermoplastic polymer is commonly referred to as a “carrier.” A typical commercial formulation of a masterbatch includes about 30% by weight of colorant, about 5% by weight of dispersant, about 10% by weight of additive, and about 55% by weight of a carrier. 
     Unfortunately, known masterbatches have a relatively low colorant concentration. Thus, it has been found that many known masterbatches have insufficient brilliance for high-quality applications. Larger proportions of colorant cannot be used in known masterbatches due to insufficient dispersion. Insufficient dispersion of the colorant particles can lead to a decrease in physical and mechanical properties of the end product, such as tensile strength, flexural modulus, elongation, and impact strength. Additional problems due to insufficient dispersion include thread breakage during spinning and clogging filters of melt spinning equipment. Accordingly, colorant concentrations have been limited in conventional masterbatches. 
     Another deficiency in known masterbatch compositions is the inability to include relatively significant amounts of additives such as ultraviolet light absorbers, light stabilizers, antioxidants, and blowing agents. Generally, additives are added only if desired and then in small amounts. Otherwise, it is believed that the processability of the masterbatch would be impaired. 
     Yet another deficiency in known masterbatch compositions is the inability to significantly improve the processability of the masterbatch itself and of the end product. For example, the melt extrusion of thermoplastics into shaped structures is generally accomplished by well-known procedures such as a reciprocating screw, injection molding, blow molding, compression molding, sheet extrusion, and fiber spinning. 
     The present assignee owns U.S. Pat. No. 7,442,742 to Smink, et al., which is incorporated by reference in its entirety. The &#39;742 patent teaches a substantially amorphous metallocene polypropylene as a processing aid in the production of color masterbatches containing high loadings of colorants and, optionally, additives. While the substantially amorphous metallocene polypropylene processing aid is very effective and provides numerous advantages over conventional compositions, it has a relatively low molecular weight and viscosity, which may in some instances limit the capability of the masterbatch composition in certain fabrication processes. 
     Accordingly, it is desirable to provide a masterbatch composition with improved processability that increases extrusion rates of the masterbatch composition as well as the end product without raising the melt temperature, while producing articles having smoother surfaces, and better physical and mechanical properties than with known masterbatches while reducing the amount of thermoplastic carrier. 
     It is also desirable to provide a masterbatch composition of colorants and optionally additives that produces better coloration of the end product while reducing the amount of thermoplastic carrier. 
     The present application, as described and claimed herein, addresses the deficiencies of prior art masterbatches. 
     SUMMARY OF THE INVENTION 
     In one aspect, the present invention is directed to a masterbatch that includes a colorant, a thermoplastic carrier, a high polymer processing aid, and optionally an additive. The high polymer processing aid can have a melt flow of less than about 200 g/10 min (ISO Condition 1133) and can be selected from the group consisting of a polybutene polymer, a polybutene copolymer, and an olefin block copolymer. 
     In another aspect, the present invention is directed to a process for making a masterbatch that includes mixing a colorant, a thermoplastic carrier, a high molecular weight polymer processing aid, and optionally an additive, and applying heat and shear to the mixture to form the masterbatch. The high polymer processing aid can have a melt flow less than about 200 g/10 min (ISO Condition 1133) and can be selected from the group consisting of a polybutene polymer, a polybutene copolymer, and an olefin block copolymer. 
     In a further aspect, the present invention is directed to a process for making a colorized polymer that includes introducing a highly-loaded masterbatch composition to a melt-processible polymer to form a melt processable polymer composition, wherein the masterbatch comprises a colorant, a thermoplastic carrier, a high polymer processing aid, and optionally an additive, and extruding the polymer composition to form the colorized polymer. The high polymer processing aid is selected from the group consisting of a polybutene polymer, a polybutene colpolymer, and an olefin block copolymer. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     While the present invention is described with reference to embodiments described herein, it should be clear that the present invention is not limited to such embodiments. Therefore, the description of the embodiments herein is merely illustrative of the present invention and will not limit the scope of the invention as claimed. 
     A masterbatch composition having a colorant, a high polymer processing aid, and optionally one or more additives is provided. This composition allows the use of standard plastic processing equipment to make relatively highly loaded color concentrates and additives. The composition including the high molecular weight polymer processing aid, exhibits excellent colorant dispersability, coloring properties, increased additive concentrations, as well as improved handleability, so that the colored end product has excellent physical and mechanical strength as well as excellent coloration. The compositions provided generally include a colorant, a thermoplastic carrier, a high polymer processing aid, and optionally additives such as antioxidants, ultraviolet light absorbers, and light stabilizers. 
     The present masterbatch composition includes a high molecular weight polymer processing aid that substantially eliminates many of the practical problems and limitations encountered in the current art. The high polymer processing aid is superior over conventional masterbatch compositions because it is compatible with various carrier resins, allows for decreasing the amount of conventional carrier resin, and provides better mechanical and physical properties of the end products. The masterbatch composition that includes the high polymer processing aid also allows for two to three times of increased concentration or loading of the colorants and additives. It also improves the colorant dispersion as well as the physical and mechanical properties of the end products. As the concentration of colorants and additives is increased, the amount of the masterbatch composition required to achieve the desired end product properties can be appreciably lower than conventional masterbatch compositions. 
     The high polymer processing aid also improves the handleability of the masterbatch composition. The masterbatch composition including the high polymer processing aid melts at lower temperatures that allow it to “wet out” or distribute more efficiently to provide better processability and increased throughput than conventional compositions. 
     The high polymer processing aid works in conjunction with the polymeric carrier to allow the masterbatch composition to include a relatively large amount of colorant that can be evenly dispersed in the presence of a high additive concentration, giving the end product excellent coloration as well as better physical and mechanical properties. Accordingly, the composition can provide molded or extruded articles having excellent mechanical strength. 
     Accordingly, the high polymer is a desirable processing aid in a masterbatch composition because it has a relatively low melt point and good binding capability. The melting point of the polymer ranges preferably from about 80° C. to about 125° C. The density of the polymer may be about 0.86 to about 0.92 g/cm 3 . The high polymer may be present in the masterbatch composition up to about 20%, preferably from about 4% to about 12%. 
     The high polymer processing aid exhibits a melt flow (ISO 1133) of less than about 200 g/10 min. The relatively high molecular weight and viscosity of the high polymer processing aid is greater than, for example, the metallocene polymer processing aid taught in U.S. Pat. No. 7,442,742, which is owned by the present assignee. The relatively high molecular weight and viscosity of the high polymer processing aid may provide a masterbatch composition superior properties in certain fabrication processes where the processing aid of U.S. Pat. No. 7,442,742 may exhibit a measurable weight loss or “burn off” at higher temperatures. Therefore, the masterbatch composition including a high polymer processing aid may have broader applicability than other known masterbatch compositions. 
     Furthermore, the high polymer processing aid may exhibit a melting temperature no more than the melting temperature of the thermoplastic carrier. For example, if the thermoplastic carrier is high density polyethylene, which typically has a melting point in its commercial form of about 120-130° C., then the high polymer processing aid may have a melting point of no more than about 120° C. The high polymer processing aid having a melting temperature of no more than about the melting temperature of the thermoplastic carrier provides the masterbatch composition with desirable binding properties to a polymer to be colored by the compositions. Also, this feature provides desirable processing characteristics when coloring a polymer with the masterbatch composition. 
     The high polymer processing aid may be a polybutene. Polybutene is a high molecular weight, isotactic, semi-crystalline thermoplastic. Polybutene combines the typical characteristics of polyolefins with a unique property mix of high flexibility and outstanding creep resistance over a wide temperature range. Due to a similar molecular structure, polybutene is very compatible with polypropylene and propylene-based thermoplastic elastomers. It is easily dispersible in polyethylene notwithstanding its limited molecular compatibility. Polybutene can be a homopolymer or a copolymer of a polybutene with one or more olefins or grafted with other polymers, such as polymerization of butene-1 and ethylene, and/or propylene comonomers. The M n  for a polybutene homopolymer may be greater than about 30,000. Copolymers of polybutene with ethylene are preferred. The ethylene or propylene content of the copolymers is from about 2% to about 20%. The melting point of the polybutene homopolymer and copolymer is about 80-125° C. 
     Alternatively, the high polymer processing aid may be an olefin block copolymer. The olefin block copolymer may be a polyethylene copolymer produced via dual metallocene catalysts. Olefin block copolymers exhibit desirable properties including improved balance of flexibility and high temperature resistance, faster set-up in processing due to higher crystallization temperature, better elastic recovery and compression set properties at both ambient and elevated temperatures, and improved abrasion resistance. The melting point of the olefin copolymer is about 118° C.-122° C. 
     The high polymer processing aid is highly compatible with various carrier resins. Illustrative examples of thermoplastic carriers are homopolymers or copolymers of high and low density polyethylene, high and low density polypropylene, polystyrene, polyoxymethylene, polyethylene terephthalate, polybutylene terephthalate, polymethyl methacrylate, polyether sulfones, polysulfones, polyether ketones, polystyrene copolymers, acrylonitrile-butadiene-styrene terpolymers, polyamides such as nylon-6 or nylon-6,6, polyvinyl chloride and copolymers of ethylene with 0.1-20 mol % of 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-decene, 1-undecene, other impact modified alloys, or mixtures thereof. The polymer to be and the carrier polymer of the masterbatch can be, but do not have to be, the same. 
     Colorants added to the masterbatch may comprise pigments, single pigment dispersions, dyes, talc filled resins, nano composites, coated micas, powdered aluminum and other metals, optical brighteners, fluorescents, phosphorescents, or mixtures thereof. Pigments may be at least one or a combination of organic pigments and inorganic pigments, and there is no particular limitation. When organic pigments are used, the organic pigments may be present up to about 50% by weight of the masterbatch composition. In a preferred embodiment, the organic pigments are present in a range from about 10 to about 40% by weight of the masterbatch composition. If inorganic pigments are used, the inorganic pigments may be present up to about 75% by weight of the masterbatch composition. In a preferred embodiment, the inorganic pigments are present in a range from about 15% to about 75% by weight of the masterbatch composition. In another embodiment, both organic and inorganic pigments are used, and the organic pigments may be present up to about 20% and the inorganic pigments may be present up to about 60%. In one embodiment, the organic pigment is present from about 3% to about 20% and the inorganic pigment is present from about 10% to about 60%. 
     Illustrative examples of the organic pigments include azo and disazo pigments such as azo and disazo lake, Hansas, benzimidazolones, diarylides, pyrazolones, yellows and reds; polycyclic pigments such as phthalocyanines, quinacridones, perylenes, perinones, dioxazines, anthraquinones, isoindolins, thioindigo, diaryl or quinophthalone pigment, Aniline Black, or mixtures thereof. Illustrative examples of the inorganic pigments include inorganic pigments such as titanium oxide, titanium yellow, iron oxide, ultramarine blue, cobalt blue, chromic oxide green, Lead Yellow, cadmium yellow and cadmium red, carbon black pigments, and mixtures thereof. The organic and inorganic pigments can be used singly or in combination. These pigments may be in any form of a dry powder, single pigment dispersions made conventionally or according to this process, or mixtures thereof. 
     Optionally, the masterbatch composition may also comprise an additive. Illustrative examples are ultraviolet light absorbers, light stabilizers, antioxidants, flame-retardants, antibacterial agents, surface tension reducers, deodorizing agents, anti-static agents, anti-blocking agents, plasticizer agents, blowing agents, fillers, and other known additives, or mixtures thereof. 
     Ultraviolet light absorbers (UVA) shield the polymer from UV light by absorbing light energy and releasing the absorbed light energy harmlessly as heat energy. Hindered amine light stabilizers (HALS) scavenge radical intermediates formed in the photo-oxidation process. The higher the concentration of UVA and/or HALS, the greater the protection of the polymer (both the masterbatch carrier and the end product) from degradation and the color from fading. UVAs and HALS can be added up to about 45% by weight of the masterbatch. Preferred UVAs and HALS include those of the TINUVIN® grades from BASF. Illustrative examples of UVA&#39;s and HALS include salicylic acid derivatives such as phenyl salicylate, p-t-butyl salicylate, etc., benzophenone system such as 2,4-dihydroxy benzophenone, 2-hydroxy-4-methoxybenzophenone, etc., benzotriazole system such as 2-(2′-hydroxy-3′,5′-di-t-butylphenyl)benzotriazole, 2-(2′-hydroxy-3′-t-butyl-5′-methylphenyl)-5-chlorobenzotriazole, etc., hindered amine system such as bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate, dimethyl succinate-1-(2-hydroxyethyl)-4-hydroxy-2,2,6,6-tetramethyl piperidine condensation product, 2-hydroxybenzophenones, e.g. 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, and 5,5′-methylene bis(2-hydroxy-4-methoxybenzophenone); 2-(2′-hydroxyphenyl)benzotriazoles, e.g. 2-(2′-hydroxy-5′-methylphenyl)benzotriazole, 2-(2′-hydroxy-5′-t-octylphenyl)benzotriazole, 2-(2′-hydroxy-3′,5′-di-t-butylphenyl)benzotriazole, 2-(2′-hydroxy-3′,5′-di-t-butylphenyl)-5-chlorobenzotriazole, 2-(2′-hydroxy-3′-t-butyl-5′-methylphenyl)-5-chlorobenzotriazole, 2-(2′-hydroxy-3′,5′-dicumylphenyl)benzotriazole, and 2,2′-methylene bis(4-t-octyl-6-benzotriazolyl)phenol; benzoates, e.g. phenylsalicylate, resorcinol monobenzoate, 2,4-di-t-butylphenyl-3′,5′-di-t-butyl-4′-hydroxybenzoate, and hexadecyl-3,5-di-t-butyl-4-hydroxybenzoate; substituted oxanilides, e.g. 2-ethyl-2′-ethoxyoxanilide and 2-ethoxy-4′-dodecyloxanilide; cyanoacrylates, e.g. ethyl-α-cyano-β,β-diphenylacrylate and methyl-2-cyano-3-methyl-3-(p-methoxyphenyl)acrylate, and any other known UVA, or mixtures thereof. 
     Additional illustrative examples of HALS include 2,2,6,6-tetramethyl-4-piperidylstearate, 1,2,2,6,6-pentamethyl-4-piperidylstearate, 2,2,6,6-tetramethyl-4-piperidylbenzoate, bis(2,2,6,6-tetramethyl-4-piperidylsebacate, bis(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate, tetrakis(2,2,6,6-tetramethyl-4-piperidyl)-1,2,3,4-butane tetracarboxylate, tetrakis(1,2,2,6,6-pentamethyl-4-piperidyl)-1,2,3,4-butane tetracarboxylate, bis(1,2,2,6,6-pentamethyl-4-piperidyl)-di(tridecyl)-1,2,3,4-butane tetracarboxylate, bis(1,2,2,6,6-pentamethyl-4-piperidyl)-2-butyl-2-(3′,5′-di-t-butyl-4-hydroxybenzyl)malonate, 1-(2-hydroxyethyl)-2,2,6,6-tetramethyl-4-piperidinol/diethyl succinate polycondensate, 1,6-bis(2,2,6,6-tetramethyl-4-piperidylamino) hexane/dibromoethane polycondensate, 1,6-bis(2,2,6,6-tetramethyl-4-piperidylamino)hexane/2,4-dichloro-6-t-octyl amino-s-triazine polycondensate, 1,6-bis(2,2,6,6-tetramethyl-4-piperidylamino)hexane/2,4-dichloro-6-morpholino-s-triazine polycondensate, and the like, or mixtures thereof. 
     Antioxidants, including processing stabilizers, can be added to the masterbatch composition up to about 15% by weight of the masterbatch. Peroxide polymer degradation generally occurs during processing (due to heat or shear), or at the time of light exposure. Peroxide radicals may be formed during this period, which in turn may lead to the formation of hyperoxides. Antioxidants are incorporated into polymers to stabilize peroxide radicals to prevent degradation. Optimal polymer stability is achieved when the initial molecular weight and/or the initial color of the polymer is maintained. Therefore, the present masterbatch composition provides a higher degree of protection by achieving higher additive concentrations without sacrificing colorant concentration. In one embodiment, both UVAs (and/or HALS) and an antioxidant may be added up to about 60% by weight of the masterbatch. It is preferred in such embodiments that the UVAs (and/or HALS) are added up to about 45% by weight of the masterbatch, and the antioxidant is added up to about 15% by weight of the masterbatch. Sterically hindered phenols or HALS are preferred antioxidants, particularly sterically hindered phenols of the Irganox® grades from BASF. Other illustrative examples of antioxidants include a phenol system such as 2,6-di-t-butyl-p-Cresol, pentaerythritol-tetrakis-(3,5-di-t-butyl-4-hydroxyphenyl)propionate methyl phenol, octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, etc., phosphorus system such as tris(2,4-di-t-butylphenyl)phosphate, distearylpnetaerythritol diphosphate, tetrakis(2,4-di-t-butylphenyl)-4,4′-biphenylene phosphonate, etc., sulfur system such as distearyl-3,3′-thiodipropionate, pentaerythritol-tetrakis-(3-laurylthiopropionate), hindered phenol type antioxidants and peroxide decomposers, HALS (as set described above), or mixtures thereof. 
     Illustrative examples of hindered phenol type antioxidants are 2,6-di-t-butyl-4-methylphenol, styrenated phenol, n-octadecyl-3-(3,5-di-t-butyl-4-hydroxylphenyl)propionate, 2,2′-methylene bis(4-methyl-6-t-butylphenol), 2-t-butyl-6-(3-t-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenylacrylate, 2-[1-(2-hydroxy-3,5-di-t-pentylphenyl)ethyl]-4,6-di-t-pentylphenyl acrylate, 4,4′-butylidene bis(3-methyl-6-t-butylphenol), 4,4′-thio-bis(3-methyl-6-t-butylphenol), alkylated bisphenol, tetrakis[methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)-proprionate]methane, 3,9-bis[2-{3-(3-t-butyl-4-hydroxy-5-methylphenyl)-propionyloxy}-1,1-dimethylethyl]-2,4,8,10-tetraoxyspiro[5.5]undecane, or mixtures thereof. 
     Illustrative examples of peroxide decomposers are organic phosphorus type peroxide decomposers, such as trisnonylphenylphosphite, triphenylphosphite and tris(2,4-di-t-butylphenyl)phosphite; and organic thio type peroxide decomposers, such as dilauryl-3,3′-thiodipropionate, dimyristyl-3,3′-thiodipropionate, distearyl-3,3′-thiodipropionate, pentaerythrityltetrakis(3-laurylthiopropionate), ditridecyl-3,3′-thiodipropionate and 2-mercaptobenzimidazole, or mixtures thereof. 
     Illustrative examples of flame-retardants are phosphoric acid systems such as allyl diallyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, triallyl phosphate, tributyl phosphate, triphenyl phosphate, tris(β-chloroethyl)phosphate, tris(dichloropropyl)phosphate, tris(2,3-dibrompropyl)phosphate, tris(bromo-chloropropyl)phosphate, etc., chlorine system such as chlorinated paraffin, chlorinated polyphenyl, perchloropentacyclodecane, etc., bromine system such as tetrabromoethane, tetrabromobutane, hexaborombenzene, decabromodiphenyloxide, polydibrornophenyloxide, bis(tribromophenoxy)ethane, ethylene bisbromonorbornane dicarboxylmide, ethylene bistetrabromophthalimide, etc. reaction type such as chlorendic acid anhydride, tetrabromo phthalic anhydride, tetrabromo bisphenol A, dietoxy-bis-(2-hydroxyethyl)-aminomethyl phosphate, dibormcresyl alycidyl ether, etc, or mixtures thereof. 
     Illustrative examples of antibacterial agents include, phenol ether based antibacterial agents, such as those having the phenol group in the intramolecular skeleton, for example, 10,10′-oxybisphenoxa arsine, etc.; natural antibacterial agents, such as those having tropolone as a central skeleton, for example, hinokitiol, β-dolabulin, etc., as glycerol ester of fatty acid, lower fatty acid monoglycerol ester, sucrose fatty acid ester, polyglycerol fatty acid ester, for example, monoglyceride caprylate, monoglyceride caprate, lauric acid monoglyceride, Sugar-ester palpitate, decaglycerol monocaprate, hexaglycerol caprylate, etc., zeolite-based compounds, part or whole of ion-exchangeable ion in zeolite-based compounds, for example, part or whole of sodium ion, calcium ion, potassium ion, magnesium ion, iron ion, etc. is substituted with ions with antibacterial property, such as silver ion, copper ion, zinc ion, ammonium ion, etc. can be exemplified. These compounds can be used singly or two or more kinds of them can be used in combination. 
     Fillers are typically inexpensive particulate materials that do not contribute to the color. Illustrative examples of fillers include, among others, talcs, micas, clays, nano-clays, silicas, or mixtures thereof. 
     The masterbatch composition described herein may contain other additives or ingredients and should not be limited to the stated formulations. In one embodiment, a dispersion package can be added to the masterbatch composition in an amount up to about 25% by weight of the masterbatch. In another embodiment, the dispersion package is added in an amount from about 2% to about 8% based on the weight of the masterbatch. The dispersion package can be waxes, metal salts, surfactants, coupling agents, organometallic compounds, and mixtures thereof. Illustrative examples include conventional polyethylene and polypropylene waxes and derivatives thereof such as acid-modified products and metal salts of acid-modified products, as well as zinc stearate, magnesium stearate, aluminium stearate, calcium stearate and ethylene bisteramide, and mixtures thereof. 
     Before actual mixing of the masterbatch, the components can be premixed if desired, for which drum or tumbler mixers may be used. In the actual mixing process, the mixing is generally performed in a high intensity mixer. In one embodiment, the masterbatch is prepared by mixing the components in a Henschel-type mixer for up to 30 minutes, preferably for 4 to 10 minutes. It is understood that the masterbatch components may be added together and mixed, or added individually at any point during the mixing process. Actual dispersion generally takes place in a single-screw or twin-screw extruder; however, any equipment known in the art may be used. Illustrative examples include Buss kneaders, planetary roll extruders, open double-trough kneaders, rapid stirrers, internal fluxing mixers such as Banbury mixers and Farrel continuous mixers, or the like. 
     The masterbatch may be introduced to any compatible polymer and processed. It is understood that the masterbatch composition of the present invention can be used for coloring polymers formed into various shapes, such as sheet, film, tube, bottles, containers, molded products and other molded articles. The term processing is used herein to describe the conversion of polymers into articles of a desired shape. Illustrative examples of processing are extrusion molding, injection molding, blow molding, compression molding and calendering. The term processable is used herein to mean capable of processing. The addition of the masterbatch to the melt-processible polymer can be accomplished by any means known in the art. It is possible to use the same methods as for preparing the masterbatch itself. It is understood that the masterbatch carrier polymer can be the same or different than the melt-processible polymer. The masterbatch composition may be introduced and processed via a batch or continuous process. In one illustrative embodiment, the masterbatch may be introduced to the melt-processible polymer and processed on a rubber compounding mill, simple kneader, or in a Banbury or other internal mixer or in a mixing extruder. Alternatively, the masterbatch can be metered to the feed section of an extruder by appropriate devices. Continuous processes can be carried out, for example, in rapid mixers, single-screw extruders, twin-screw extruders, Buss kneaders, planetary roll extruders, open double-trough kneaders or rapid stirrers. Continuous processes are preferred. 
     EXAMPLES 
     The following masterbatch examples set forth in Table 1 below were prepared in accordance with the invention and are intended to illustrate the invention without, however, limiting it. The percentages shown in Table 1 below are percent by weight of the total masterbatch composition. 
     
       
         
           
               
               
               
             
               
                   
               
               
                 Materials 
                 Example 1 
                 Example 2 
               
               
                   
               
             
            
               
                 Carrier Resin 
                 11.0% (Linear Low 
                 15.7% (High Density 
               
               
                   
                 Density Polyethylene) 
                 Polyethylene) 
               
               
                 Processing Aid 
                 7.0% 
                  6.0% 
               
               
                 Colorant 
                 80.0% (TiO 2 ) 
                 39.5% 
               
               
                 UV Stabilizer 
                 — 
                 31.5% (Tinuvin) 
               
               
                 Anti-Oxidant 
                 — 
                 5.3% (Irganox) 
               
               
                 Dispersion Package 
                 2.0% (Zn Stearate) 
                 2.0% (Zn Stearate) 
               
               
                   
               
            
           
         
       
     
     Table 1 above demonstrates that addition of the high polymer processing aid to the masterbatch composition allows for a higher colorant and additive concentration with a lower carrier concentration than conventional masterbatches. Example 1 shows a masterbatch composition having a high concentration of pigment. Example 2 shows a masterbatch composition having a high concentration of pigment and additives. The masterbatch compositions in Examples 1-2 were processed on standard laboratory and commercial scale extrusion equipment to yield fully compounded pellets. In both examples the following processing aids were used with substantially the same results: (1) a homopolymer polybutene resin with melt flow of 200 g/10 min and melt point of about 124° C., (2) a copolymer polybutene resin with &gt;10% ethylene comonomer that has a melt flow of about 40 g/10 min and a melt point of about 81° C., (3) and a olefin block copolymer of polyethylene made by shuttling the chain between two catalysts and having a melt flow of about 15 g/10 min and a melt point of about 120° C. 
     The resulting pellets formed from the masterbatch compositions in Examples 1-2 were evaluated for pigment dispersion quality and pellet integrity. Dispersion was assessed visually using thin, pressed-out films of the masterbatch composition. Pellet integrity was evaluated by applying pressure to individual pellets. The pellets deformed rather than break apart. 
     The invention has been described above and, obviously, modifications and alternations will occur to others upon a reading and understanding of this specification. The claims as follows are intended to include all modifications and alterations insofar as they come within the scope of the claims or the equivalent thereof.