Compositions for manufacturing fiber-reinforced, starch-bound articles having a foamed cellular matrix

Abstract

Compositions, methods, and systems for manufacturing articles, particularly containers and packaging materials, having a fiber-reinforced, starch-bound cellular matrix. Suitable mixtures used to form the articles are prepared by first preparing a viscous preblended mixture comprising water, a gelatinized starch-based binder, and fibers having an average length greater than about 2 mm. The highly viscous preblended mixture effectively transfers the shearing forces of the mixer to the fibers. The final moldable mixture is then prepared by mixing into the preblended mixture the remaining starch-based binder, water, and other desired admixtures, e.g., mold-releasing agents, inorganic filler rheology-modifying agents, plasticizers, coating materials, and dispersants, in the correct proportions to form an article which has the desired performance criteria. The moldable mixtures are heated between molds at an elevated temperature and pressure to produce form-stable articles having a desired shape and a selectively controlled foamed structural matrix. The articles may be manufactured to have properties substantially similar to articles presently made from conventional materials like paper, paperboard, polystyrene, plastic, or other organic-based materials and have especial utility in the mass-production of containers, particularly food and beverage containers.

Description

[0001]This application is a continuation-in-part of U.S. Ser. No. 08 / 288,664, filed Aug. 9, 1994, now allowed, and a continuation-in-part of U.S. Ser. No. 08 / 288,667, filed Aug. 9, 1994, pending U.S. Ser. No. 08 / 288,667 is a continuation-in-part of U.S. Ser. No. 08 / 218,971, filed Mar. 25, 1994, pending, and a continuation-in-part of U.S. Ser. No. 08 / 109,100, filed Aug. 18, 1993, now abandoned, and a continuation-in-part of U.S. Ser. No. 08 / 095,662, filed Jul. 21, 1993, now U.S. Pat. No. 5,385,764, and a continuation-in-part of U.S. Ser. No. 07 / 982,383, filed Nov. 25, 1992, now abandoned, and a continuation-in-part of U.S. Ser. No. 07 / 929,898, filed Aug. 11, 1992, now abandoned. U.S. Ser. No. 08 / 288,664 is a continuation-in-part of U.S. Ser. No. 07 / 928,898, filed Aug. 11, 1992, now abandoned. For purposes of disclosure of the present invention, each of the foregoing applications is incorporated herein by specific reference. BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0...

AI Technical Summary

Benefits of technology

[0033]It has been discovered that the long-length fibers dispersed throughout the moldable mixture and, hence, the final molded article serve at least two important functions. For and perhaps most importantly, the fibers reinforce the newly foamed and gelated starch-bound matrix, so that the molded article can be removed from the mold while retaining adequate moisture within the structure of the article to plasticize the starch-bound matrix. This allows the newly demolded article to have adequate toughness and strength immediately or shortly after being demolded for its intended purpose without the need for conventional conditioning, as was previously required in the manufacture of foamed starch-based articles. Without the conditioning step to reintroduce moisture back into the starch-based matrix, foamed starch-based articles, even those that include quantities of shorter-length fibers, were usually too brittle and fragile for their intended use. Moreover, such articles could not simply be demolded without such overdrying because of the destructive nature of the highly pressurizing water vapor that otherwise would remain within the cellular structure of the newly demolded article. The convenient starch-based cellular matrix alone was simply not strong enough to withstand the internal buildup of pressure caused by the heated molding process.

[0074]Finally, a further object and feature of the present invention is to provide compositions and methods that allow for the production of highly inorganically filled, starch-based materials having greater flexibility, flexural strength, toughness, moldability, mass-producibility, product stability, and lower environmental impact compared to conventionally manufactured starch-based materials.

Problems solved by technology

Without the conditioning step to reintroduce moisture back into the starch-based matrix, foamed starch-based articles, even those that include quantities of shorter-length fibers, were usually too brittle and fragile for their intended use.

Moreover, such articles could not simply be demolded without such overdrying because of the destructive nature of the highly pressurizing water vapor that otherwise would remain within the cellular structure of the newly demolded article.

The convenient starch-based cellular matrix alone was simply not strong enough to withstand the internal buildup of pressure caused by the heated molding process.

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