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Interlocking additive effects forcing total-system approach.

Interlocking Additive Effects Forcing Total-System Approach

The plastics industry is at a fork in the road. Essentially, its progress is forced by the opportunites and pressures of continued growth and widening applications that require improved functional properties, durability, and cost levels.

One route is the development of new polymers. However, the inherent difficulty, expense, and time delay in creating new polymers have made this route a lightly traveled one.

The alternative route is to optimize existing polymers through use of additives as property enhancers. This route is now much more heavily traveled by materials suppliers, compounders, molders, and designers. Long considered the quiet workhorse of the plastics industry, additives technology now has moved into a position of greater prominence. Additives are recognized, more than ever, as critical elements in the quest for higher-performance, more durable, and lower-cost plastic end-products.


Additives have become much more of a factor in the effort to achieve improved material properties. Bruce Mulholland, color development engineer, Hoechst Celanese, says that "we are increasingly aware today of the synergism between different additives in a formulation. In the development of a new ultraviolet-stable acetal resin, Celcon UV 90Z, for example, we found that the concentration of antioxidant was extremely influential on the degree of ultraviolet stability. A total-system approach has become essential in order to optimize the synergistic effects on the resin's performance. There is now much more awareness of the interrelation between stabilizers and color, for instance, especially with the growing interest in organic pigments and dyes and their greater potential for interaction."


Although environmental pressures continue to increase, cadmium basically is in a state of limbo relative to the enactment of federal legislation against its use. If passed, federal bill S112, introduced by Sen. John H. Chafee (R-R.I.), would ban pigments containing cadmium and would become effective 12 months after enactment. Action on the bill, however, is not expected prior to 1990.

The original cadmium issue has now broadened in scope. Jack Graft, technical manager, Pigments Dept., Dyes, Pigments, and Organics, Mobay Corp., points out that 10 to 15 years ago the focus was almost exclusively on minimizing worker exposure. With mounting environmental activity regarding incineration and landfill, the pressure now is building to limit plastic products as a source of cadmium in the waste stream.

Moreover, considering the likelihood that cadmium may increasingly become an issue that could affect international marketing, U.S. manufacturers are becoming more aware of potential advantages of producing plastic products that can be sold anywhere in the world and are in compliance with applicable regulations.

Combining opacity and heat the light stability, cadmium pigments range from greenish through reddish yellows, and orange, red, and maroon. Graff comments that the movement under way to reformulate colors without cadmium could have negative impacts on color styling. Engineering resins, with their higher processing temperatures, for example, could be especially affected by the elimination of cadmium pigments from color formulations.

The development of high-opacity, more heat-stable organic pigments and dyes now is a major effort. Graff says that a combination of high-performance organic colorants, coupled with inorganic pigments for opacity, can sometimes be effective if compromises with respect to metamerism, processability, and cost can be accepted. However, though many colorants can be effectively matched, there are still problems in maintaining ligh-fastness.

Graff says that contrary to the erroneous belief about the color stability and temperature limitations of dyes, many of them have good to excellent lightfastness and outstanding heat stability. Still, he asserts that while dyes can be strong contenders, compromises are inevitable, because of their transparency and sometimes limited lightfastness, compared with the inherent capabilities of colors formulated with cadmium. Although dyes generally are compatible with engineering resins, there remains a basic limitation to their use in olefin-based products because of blooming to the surface. Options for polypropylene and other olefins, in the event of a ban on cadmium, could include use of organic pigments, possibly in conjunction with lower processing temperatures and/or modified mold or part design that would allow shorter cycle times.

With the impending congressional action, the cadmium issue is gaining momentum. Some companies have taken the position that they will not use cadmium in new pigment formulations. Nevertheless, in spite of numerous advancements in the search for possible alternatives, Graff does not yet see anything on the horizon that can provide the stability and color features of cadmium pigments.


Ciba-Geigy's work on new, improved stabilizers to meet high processing and end-use temperatures includes numerous new chemistries and improvements on traditional ones. Phenolic antioxidants for heat stability, phosphite processing stabilizers, and hindered amine light stabilizers are among the additive materials being researched.

Significant growth in the polypropylene fiber market, notably in the automotive industry, has increased the need for a wider breadth of color, as well as improved light and high-temperature stability. One factor is the need to prevent, or compensate for, the color effects of numerous additives in the material's formulation.

Also, tougher stabilization requirements of polyethylene film for packaging are forcing new approaches to improving conventional systems, with some combinations creating synergistic effects that still must be resolved for optimum product effectiveness.


Ampacet Corp., the largest independent manufacturer of color and additive concentrates for polyolefins, recently inaugurated a $20 million expansion of its Terre Haute, Ind., color and additive concentrate plant. The expansion, which brings the facility's annual capacity to 250 million lbs, documents the company's strong confidence in the growth of world markets for masterbatches.

Ampact designed the expansion with an awareness of the increasing emphasis on providing uniform, high-quality products as the best way to sustain market and company growth. The result is the installation of two new, highly automated, statistical-process-controlled production lines, each under the supervisory control of a sophisticated industrial computer. The plant utilizes, form raw material handling to order packing, the latest in microprocessor-controlled equipment. Ampacet says many of the system components were custom-made to its specifications.

All manufacturing conditions, ingredients, and proportions for a concentrate formula, either developed by Ampacet or tailored to a customer's requirements, are stored in computer files. The data ensure precise batch-to-batch repeatability, regardless of order size or elapsed times between orders. Automated packaging lines communicate with the on-line computer. Key installations include a Berstorff twin-screw continuous extrusion line, a continuous production line from Pomini, and raw material handling units from Chronos Richardson.

The Terre Haute operation produces a wide range of additive concentrates, including degradables, flame retardants, foaming agents, UV absorbers, antistats, slip additives, antioxidants, antiblock agents, carbon black, and multifunctional formulations. The plant expansion allows Ampacet to be able to supply more than 60% of total U.S. requirements for polyolefin additive and color concentrates.

Martin J. Fernandi, vice president, sales and marketing, estimates the total U.S. market for all concentrates, includes all producers, at about 700 million lbs/yr. Of the total, the polyolefins take up from 400 to 500 million lbs. About 40% of the masterbatches are white, 20% black, 25% other colors, and 15% are "other additives." Fernandi says that Ampacet now is "looking at other resins, probably initially nylon and polycarbonate."

The Terre Haute plant is one of Ampacet's four manufacturing sites. The other U.S. facilities are in Mt. Vernon, N.Y., and DeRidder, La. Since 1986, a state-of-the-art computerized production facility has been operational in Messancy, Belgium.


GE Plastics Specialty Chemicals' recent announcement of a planned $15 million investment this year reflects the company's expectation of increased global growth. Included is an $8 million expansion at Washington, W. Va., of the Blendex modifier resins, which are used to improve toughness, heat-distortion temperatures, thermoplasticity, and processing in PVC and other polymers.

Expansions in Morgantown, W. Va., will include added production capacity of Weston liquid and solid phosphite stabilizers, used to improve ultraviolet stability of polymers. GE Specialty Chemicals is the world's largest phosphite producer. Also, $3 million allocated for design for increased resource conservation.

GE Specialty Chemicals also produces Ultranox antioxidants for polyolefins, PVC, polyester, polycarbonate, high-impact polystyrene, ABS, elastomers, and alkylated products.

Plans call for additional expansion of $10 million next year, with an expectation of future investments of $10 million per year during the next several years.

Recycling. Roger Wilson, marketing manager, modifier resins, GE Specialty Chemicals, says that additives can, initially or during reprocessing, increasingly help polymers meet environmental requirements. Impact modifiers, stabilizers, antioxidants, and process aids can extend the life of polymers and thus reduce waste.

Commingled recycled polymers, as well as single-source regrind, often need an upgrading in impact properties. Blendex 336 and 338, Wilson says, improve processability and impact strength in PVC, polyurethanes, polyesters, polycarbonate, epoxies, ABS, SAN, and other engineering thermoplastics that are being reprocessed into new applications.

The addition of Blendex 424, a new clear impact modifier specifically designed for PVC packaging applications, provides high transparency, toughness, and good printability. Also new, Bledex 590 permits lower concentrations for foam PVC profiles and sheet. Increased hot melt strength, lower densities, and more uniform melt elongation are provided for improved fabrication, especially stretching, blowing, and thermoforming, of rigid and semirigid foams.

Because of contamination and prior heat histories, recycled polymers are particularly susceptible to degradation during compounding and processing. Elyse Lewis, marketing manager, stabilizers, says that adding phosphite antioxidant products, such as Ultranox 626, 875, and 877, has been shown to prevent viscosity loss during processing of recycled polyester and polyethylene bottles, while also preventing discoloration. Ultranox 626, a free-flowing solid phosphite, displays excellent processing and color stabilization. "Processors of recycled plastics are looking to markets that offer a higher value for their products," Lewis adds. "Stabilization of recycled plastics with phosphites can result in polymers with better color and improved physical properties, making the polymer more useful in new applications."

High heat applications. Increased demand has been evident for PVC applications with higher use temperatures, such as pipe for conveying hot liquids, industrial sheeting, water bottles, injection molded parts for computer housings, and electrical and telecommunications devices. In building, there is an increased interest in improved modifiers to limit heat distortion and to avoid "oil canning" and warpage problems of darker-colored vinyl siding and exterior profiles. GE Specialty Chemicals maintains that its Blendex 586 and 702 high-heat modifiers can upgrade PVC compounds with marginal temperature performance.

Alloy/blend stabilization. Antioxidant stabilization systems are expected to be a key factor in the development of future polymer alloys and blends. Stabilization normally can be difficult because of inherent differences in polymers--certain polymers require more or different stabilization than others because of their chemistry and the amount of heat and shear they encounter in typical downstream processing steps. A rubbery or elastomeric material, for example, when blended with a high-temperature engineering plastic, such as a polyester, may not retain its elastomeric properties if it is subjected to high processing temperatures without proper stabilization. Phosphite antioxidants, however, are available that are effective in reducing molecular weight degradation and discoloration in many polymers, and because the antioxidants are beneficial to both components, the blend can be effectively stabilized.


Polycom Huntsman's specialized product line of five years ago, filled polypropylenes for the automotive market, now has broadened to include a wide range of color concentrates and additives, such as ultraviolet, slip, and antiblock products. While maintaining its custom compounding markets in automotive, the company has also expanded its customer base in areas such as appliances and power tools.

Kiyo Hattori, vice president, operations, says that active work on photobiodegradable technology could result in a new product within the next 12 months. Recognizing the almost relentless environmental trend, the company no longer uses cadmium pigments and is minimizing as much as possible the use of lead chromates.

In response to another trend, for higher concentrations in additive packages, Polycom Huntsman has introduced four new products, all in polyethylene carriers, that are aimed at being more competitive with existing grades with lower percentage loadings. D26264, a TiO.sub.2., has an 80% concentration, compared with the typical 50% to 60%. Similarly, a new inorganic filler antiblock additive, A27305, also features an 80% concentration. A new carbon black concentrate, B26669, with 60% loading, compares with the typical 40% to 50% concentrations. Finally, Polycom Huntsman's new fatty amide slip additive, A27018, doubles the normal 5% concentration to 10%.

Hattori emphasizes that the increase in percentage loadings spells better supply and production economics, since the supplier needs to compound less material for a given formulation and the molder uses less volume of packaged concentrate in his handling and processing operations.


Argus Div. of Witco Corp. is now offering a series of liquid and powder products, in its recently introduced line of Mark 4700 and 6700 non-cadmium heat stabilizers. Mark 4700 liquid stabilizers include variations for highly filled and clear calendering, extrusion, plastisol, and other flexible applications.

The 6700 series powder stabilizers include specific formulations for general-purpose, high-performance automotive, and rigid uses. The products provide alternatives for PVC compounders and end-users who seek more options in complying with EPA and OSHA regulations and California's Proposition 65 governing the use of cadmium metal in heat stabilizers.

For coextruded products in the vinyl siding market, the company provides a group of tin stabilizers. The recently developed Mark 1965 methyltin enhances weathering chalking resistance in dark colors for capstock. Argus also offers the established methyltins, Mark 1900 or 1936, for different efficiency levels, and an economical methyltin, Mark 1971, for the base stock.

Argus also sees more interest in heat stabilizers for PVC blown bottles, which, at a cost lower than PET and with good processability, have captured a significant share of the bottled water market in Europe. A calcium-zinc stabilizer, Mark 3704, provides color retention properties and low odor and taste characteristics. While the bottled water market is not large in the U.S., the easily processed PVC bottles could lead to broader general-purpose applications, such as salad oils.

Although the overall pipe market has matured, heat stabilizer technology for foam core PVC non-pressure pipe also is attracting more attention. Argus' methyltin, Mark 1925, is being used to stabilize foam core stock, and another methyltin, Mark 1915, is compounded for extrusion of foamed profiles and interior moldings.

Argus has been encouraging stabilizer users to avoid drum disposal and to use returnable tote bins, which can be provided.

Polymer compounders are evaluating oleochemical-based processing agents to increase injection molding efficiency. They are seeking more uniform, predictable processing charactersitics, such as flow and fast ejection from the mold cavity, that will facilitate modifying basic resin formulations to meet a wider range of molding requirements. Agents suited to specific resin systems are being investigated to obtain more efficient internal lubrication that will optimize processing operations.

Witco's Humko Chemical Div., extending its oleochemical-based internal mold release technology to additional resin systems, now offers MoldPro agents especially suited for foamed polyethlene, polycarbonate, phenolic, and polysulfone, as well as for other engineering polyolefin systems. The additives can function as alternatives to silicone or fluorocarbon spray-on agents, which must be applied periodically to the mold, can cause residue buildup, or can interfere with application of coatings on plastic parts.

Humko Chemical has also introduced enhanced amide products that act as fast, migrating slip additives for polyolefin films. Kemamide E 757 and Kemamide E amides provides a faster rate of slip development (bloom rate), while retaining low volatility and good suitability for food applications.

Earlier this year, Witco announced plans for expansion of Humko's Newark, N.J., plant to manufacture bisamides and esters derived from fatty acids. One of the major applications for Kemamide W-40 ethylene bistearamide and other bisamide waxes to be made at the plant is internal lubrication for PVC molding compounds.

Witco has received NSF potable water certification for its calcium stearate/wax composite, Lubricant WS-1, which was already accepted as an external and internal lubricant for nonpotable piping and other rigid PVC compound applications. The composite product enables compounders and processors to add internal and external lubricant to their compounds in a single step.

The company reports that the prill form (small spherical shapes) of Sunkolite paraffin was lubricant it introduced a year ago has been well received by PVC molders. The traditional forms of this wax have been flake and powder, but prills have been found easier to handle, both mechanically and manually. The wax is used as an external lubricant for rigid compounds.

Earlier this year Witco announced plans to build a $6 million stearate manufacturing facility, at its plant complex in Houston, which will increase the company's stearate production capacity by 35%. Complextion of the project is scheduled for next summer.


John R. Lindstrom, project manager, Reed Plastics, Div. of Sandoz Chemicals Corp., a manufacturer of color concentrates, notably for engineering plastics, cites the company's development of stabilizer additive systems for injection molded nylon 6 and 6/6 to meet stringent weathering requirements of colorants for automotive applications. He says the stabilizer systems prevent color fade, chalking, and cracking due to heat and sun exposure. Lindstrom adds that for PET materials for bottles, film, and formed sheet, Reed also has developed additives such as UV stabilizers, denesting and antiblocking agents, and antioxidants, for new processing and end-use objectives.

The company is developing color technology for elastometric polyesters and acetal resins. A producer of customized products, Reed is now surveying its customer base with the possibility of offering a standard line of color concentrates.


Monsanto Chemical Co.'s Elix, a new family of polymer modifiers, enhances the processability and heat, impact, and weather resistance of PVC. The company says that the variety of modifiers improves PVC performance for applications such as business machine housings, television backings, automotive components, electrical parts, pipes, and profiles. Elix 100 is composed of butadiene-based impact modifiers. The 200 series, based on SAN (styrene-acrylonitrile) and AMS (alpha methyl styrene), improves processability and melt strength. SMA (styrene-maleic anhydride)-based, the 300 series is designed to improve PVC's heat resistance. The Elix 400 series, with ASA (acrylatestyrene-acrylonitrile) impact modifers, improves ultraviolet resistance.


Anzon Inc.'s dustless technology respond to the efforts of many companies to reduce dust levels in the workplace. John Little, general manager, Specialty Additives Unit, says that the Envirostrand flame-retardant and lead chemical stabilizer packages are compatible with proprietary carrier systems that could be lubricants, waxes, or plasticizers instead of base resins. As a pellet, the product is totally dustless. Included in the active package--if, for example, a flame retardant, and depending on the customer's specifications--could be antimony oxide, a halogen source, and/or zinc or molybdenum for smoke suppression, singly or in combination. Little says that most of the line, with loadings of 90% to 95% active material, consists of standard formulations intended for nylons, polyolefins, PET, styrenes, elastomers, and alloys and blends of these materials. Customized products are now in a developmental stage.
COPYRIGHT 1989 Society of Plastics Engineers, Inc.
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Author:Wigotsky, Victor
Publication:Plastics Engineering
Date:Nov 1, 1989
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