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Moldable, water-soluble starch-based resin arrives.

Moldable, Water-Soluble Starch-Based Resin Arrives

Newly commercial melt-processable, starch-based resins that disintegrate rapidly in water may one day make food trays that even an environmentalist could love. Novon polymer, developed by Warner-Lambert Co., Morris Plains, N.J., is a fully biodegradable plastic-like material, media primarily of corn and potato starch and water (see PT, March '90, p. 14; Sept. '90, p. 122; Dec. '90, p. 83). Some grades are over 90% starch. Initial grades are designed to disperse rapidly in water. A recently commercialized extruded foam packing material, for instance, reportedly disintegrates in under 2 min into a harmless, solution that can be washed down the drain.

First commercial grades, announced in June, are Novon 2020 for extruded foam and Novon 3001 for injection molding. A second developmental injection molding grade (4001) is designed for less rapid disintegration. Novon 2020 has been used commercially to make foamed loosefill packaging nuggets since July at Storopack Inc., Cincinnati, and at Storopack-Reichenecker in Germany. Using water as a foaming agent, Storopack extrudes a spongy double tube, then cuts it to 1-in. bits. By October, Storopack hopes to be extruding Novon at all its 18 U.S. plants.

Novon was originally developed in the 1980s by Warner-Lambert's Basel, Switzerland, R&D labs, to make drug capsules. The original Novon 1001 grade is used for that purpose by Warner-Lambert's Capsugel Div. Novon is reportedly covered by over 20 patents. A pilot plant in Arlesheim, Switzerland, produces 10 million lb/yr. A second pilot facility started up in New Jersey in May produces similar "developmental" quantities. As previously announced, the first major production facility, in Rockford, Ill., with nameplate capacity 100 million lb/yr, is under construction and expected to be operating in early 1992.

EASY MOLDING

Novon 3001, designed for rapid wet disintegration, has a high spiral-flow rating (25 in.) and "excellent mold release and cycle times," says marketing v.p. Rhonda Brooks. "With certain minor changes to molds and operating temperatures, it runs on commercial injection molding equipment. It molds best using externally heated hot runners and at temperatures of 275-350 F."

Slower disintegrating Novon 4001 is designed for "more flexibility," she says, targeting food-service items and personal-care products like tampon applicators. Brooks notes that starch doesn't support microbial growth unless water content is "way over 20%." Novon 4001 has lower (16-in.) spiral melt flow than 3001. Both are 30-40% denser than most commodity plastics: specific gravity for 4001 is 1.34 and for 3001 is 1.45. Glass-transition temperature and melt temperatures are also lower than for traditional plastics.

TOTAL DEGRADATION

Starch content of Novon varies from 60% to 98%. Starches are provided under a technology and supply agreement with National Starch and Chemical Co., Bridgewater, N.J. (which last November began shipping its own Eco-Foam starch-based packing material). Novon Products Div. won't disclose remaining Novon ingredients, but says additives (like [TiO.sub.2] or calcium carbonate for whiteness) are all biodegradable or "naturally occurring and nontoxic."

Speed of disintegration isn't a function of how much starch is used, but of the type of starch and of processing technology, says Novon director of process engineering Bharat Mehta. "Even 98%-starch material could be less readily dissolvable if the starch is specially produced from certain hybrid feeds that are more resistant to moisture. Some starches are also more expensive to produce because they have to cook for a long time at high temperatures. It's amazing what you can do with starch itself, without synthetics or chemicals."

Starch is a repeating glucose polymer, containing straight amylose chains resistant to water, and high-molecular-weight, branched amylopectin chains. Commercial high-amylose (70%) starch is used in Eco-Foam. National Starch is developing new hybrids with 80-90% amylose. Novon also has R&D teams in New Jersey and Switzerland working on new grades for film, sheet, extrusion, blow molding and foamed sheet. More water-resistant grades will be needed for applications like disposable cutlery, thermoformed trays, clamshell containers, drink lids, straws, margarine tubs, dairy containers, portion packages, candy wrap and film for metal-paper-plastic laminations. Novon says it has secrecy agreements with several dozen companies developing such applications. "We've made foamed sheet in lab conditions and it's beautifully compostable, but the material needs to be tweaked to get the properties we want for thermoforming," Brooks says. Fully degradable thermoformed foam that's compostable and eliminates roadside litter, could be a powerful contender for fast-food and medical applications where recycling isn't likely to work.

Since total degradation is Novon's main selling point, it won't be sold for blending with other polymers to create only slightly degradable materials, an application some other starch-based materials have sought, like masterbatch compounds from Fully Compounded Plastics Inc., a start-up company in Decatur, Ill., (see PT, Jan. '91, p. 90).

Novon resins cost $1.50-3.00/lb, depending on quantity and starch technology. The initial 2020 and 3001 grades are at the low end - $1.50-2.00/lb. Novon 3001 in natural or white will be $1.50/lb in large quantities, says Brooks. (CIRCLE 29)

ANOTHER MOLDABLE STARCH

Other starch-based plastic-like materials are also coming to market. Mater-Bi, a 60% starch-based resin from Novamont North America Inc., N.Y.C., a unit of Montedison Spa in Italy (see PT, Sept. '90, p. 122), is available in commercial quantities. Injection molding, blow molding, extrusion and thermoforming grades of Mater-Bi are available for $2.50/lb, made at a year-old pilot plant in Terni, Italy, which will expand to 60-million-lb/yr capacity in the fourth quarter. A 100-million-lb/yr U.S. plant is planned for late 1992 or early 1993, probably on the East Coast, Novamont says.

Mater-Bi is antistatic, with low (0.6-0.7%) shrinkage and lower processing temperatures than conventional thermoplastics, Novamont says. On a 25-30:1 L/D extruder, grade AF05H extrudes at 266-293 F, grade AT05H at 284-320 F. Extrusion blow molding grade AB05H process at barrel temperatures of 266-293 F and head temperatures of 284-302 F; AB06H at barrel temperatures of 275-302 F, head temperatures of 293-311 F. Injection grade AI05H molds at 284-347 F. Injection grade A135H has slightly easier flow.

Extrusion-grade AF05H makes blown and cast films with "outstanding softness" for skin contact, and moisture barrier "similar to microporous PE," Novamont says. Thin (10-micron) film can be blown on standard PE equipment. Mater-Bi films are said to be printable without surface treatment. (CIRCLE 30)

LACTIDE RESINS COMING

Du Pont Co., Wilmington, Del., and ConAgra Inc., Omaha, Neb., recently announced a joint venture called Echochem to develop fully degradable polymers made of lactic acid from cheese whey and corn. Echochem, based in Wilmington, plans a pilot plant later this year to produce developmental quantities of the new polylactide resin. Initial grades will focus on clear film for packaging, which appear to have good moisture barrier. But grades "are potentially applicable to all standard processing technologies," says Echochem president Mark Montgomery. Formulations will also control degradability from weeks to months, he says.

Polylactides were invented in 1932. Du Pont says it has developed proprietary technology including specialized foaming equipment. Du Pont, which already produces Medisorb biodegradable lactide and glycolide polymers for medical/pharmaceutical applications (see PT, March '89, p. 14), plans a worldclass (over 100-million-lb/yr) Echochem plant by 1994 in the Midwest. Montgomery adds that polylactides "will be competitively priced with nondegradable polymers." (CIRCLE 31)

[Tabular Data Omitted]

PHOTO : Loosefill bits made of the first commercial foam grade of starch-based Novon dissolve in water in under 2 min. Other grades in development for applications like fast-food trays and cutlery will be more water resistant.
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Author:Schut, Jan H.
Publication:Plastics Technology
Date:Sep 1, 1991
Words:1259
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