Process for manufacturing compostible thin-walled molded article

Details Process for manufacturing compostible thin-walled molded article Process for manufacturing compostible thin-walled molded article

1996-06-03

1998-01-27

Tentoni, Leo B.

Plastic and nonmetallic article shaping or treating: processes

Disparate treatment of article subsequent to working,...

1061251, 1061361, 1061441, 1061451, 1061581, 1061591, 1062061, 264300, 264330, B29C 3902, B29C 7100

Patent

active

057119082

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The present invention relates to a process for manufacturing compostible thin-walled molded articles such as cups, plates, fast-food packagings, trays, flat sheets and the like, by applying a starch-based baking composition on the lower part of a multipart, preferably bipartite mold, to obtain a tough, durable article of high mechanical stability product medium- or long-chain, optionally substituted fatty acids and/or salts thereof and/or acid derivatives thereof, e.g. acid amides, as a release agent--optionally using 0.5-6.5% by weight, preferably 0.1-4.2% by weight, of polymethylhydrogen siloxanes in combination with said compounds, or as a partial or occasionally as a complete substitute thereof, such that, when both groups of compounds are used and the concentrations of fatty acids and derivatives thereof are high, normally the concentration of polymethylhydrogen siloxanes is best not allowed to exceed 3% by weight, and optionally thickening agents such as swell-starch, pregelatinized starch or baking wastes, and/or guar gum, pectin, carob gum, carboxymethylcellulose and/or gum arabic; fibrous materials such as high-cellulose raw materials, vegetable raw materials, fibers of plastics, glass, metal and carbon; non-fibrous fillers such as calcium carbonate, carbon, talc, titanium dioxide, silica gel, alumina, shellac, soybean protein powder, wheat gluten powder, chicken egg protein powder, casein powder, and caseinate powder; colorants; preservatives and antioxidants; 6-22% by weight.
Such a process is described in our U.S. Pat. No. 5,376,320. Various starches and/or flours and flour mixtures are used as starch products there.


SUMMARY OF THE INVENTION

The type of starch used to produce the molded articles together with the co-use of additives and the manufacturing conditions determine the properties (weight, density, mechanical properties and the like) of the resulting product.
It has surprisingly been found that the molded articles show significantly increased stability when in addition to or in lieu of starch at least one modified starch chosen from the group comprising starch esterified with organic acids or phosphoric acid, etherified starch, cross-linked starch and starch capable of being modified by ionic interaction is used.
While the starch derivatives used to date in the known formulations have been employed mainly because of their thickening action, e.g. pregelatinized starch, thereby keeping a check on sedimentation of individual ingredients of the baking composition, the additives of the invention are found to have an effect on structure formation and stability.
Starch, most important natural starches consisting of amylose (17-31%) and amylopectin (69-83%), is organized in granular structure, one grain consisting of a large number of amylose and amylopectin molecules of high chain length (greater than 1000 glucose units). Per glucose unit 3 OH groups of amylose are available for substitution, equally so with amylopectin, with the exception of the branching positions, here 2 free OH.
Starch derivatives are characterized by several important indicators: glucose unit Maximum=3, frequently used from less than 0.001 to 0.2, i.e. less than 1 to 200 substituted positions per 1000 glucose units % substitution (% by weight substituents in total dry substance) and determinability.
The said starch derivatives (esterified starch, etherified starch and cross-linked starch) are outwardly (microscopically) unchanged granules of starch. They must show two mutually balanced activities. etherification i.e. water binding and gelatinization at lower temperatures. Consequence: faster, further-reaching gelatinization during the baking process, thus better exploitation of the "binding force" of starch. and retained, but no unlimited swelling and thus bursting of the grain. A denser and more stable structure as a result. ##STR1##
R=CH.sub.3 acetylation, DS up to 0.12
R=CH.sub.2 --CH.sub.2 --COOR.sub.1 succinylation, max. 4% succinic anhydride
R.sub.1 =H, Na or other counterion, depend

REFERENCES:
patent: 4076846 (1978-02-01), Nakatsuka et al.
patent: 5320669 (1994-06-01), Lim et al.

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