Compositions and methods for manufacturing starch-based sheets
First Claim
1. A method for manufacturing a starch-bound sheet comprising the steps of:
- (a) providing a starch-based mixture including water, initially ungelatinized starch granules, and an auxiliary water-dispersible organic polymer that is capable of reducing adhesion between the starch-based mixture and heated forming rollers upon gelatinization of the starch granules;
(b) forming the starch-based mixture into an initial green sheet by passing the mixture between at least one set of heated forming rollers having a temperature such that a portion of the auiliy water-dispersible organic polymer forms a layer of reduced adhesion on the outer surfaces of the initial green sheet in order to prevent substantial adhesion of the starch-based mixture to the forming rollers upon gelatinization of the starch granules;
(c) heating the initial green sheet to cause at least a portion of the starch granules to become gelatinized in order to form an intermediate green sheet; and
(d) removing at least a portion of the water from the intermediate green sheet by evaporation so as to form a starch-bound sheet having a binding matrix that includes a mixture of substantially dried starch and auxiliary water-dispersible organic polymer.
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Accused Products
Abstract
Compositions and methods for manufacturing sheets having a starch-bound matrix reinforced with fibers and optionally including an inorganic mineral filler. Suitable mixtures for forming the sheets are prepared by mixing together water, unmodified and ungelatinized starch granules, an auxiliary water-dispersible organic polymer, fibers, and optionally an inorganic mineral filler in the correct proportions to form a sheet having desired properties. The mixtures are formed into sheets by passing them between one or more sets of heated rollers to form green sheets. The heated rollers cause the auxiliary polymer to form a skin on the outer surfaces of the sheet that prevents the starch granules from causing the sheet to adhere to the rollers upon gelation of the starch. The green sheets are passed between heated rollers to gelatinize the starch granules, and then to dry the sheet by removing a substantial portion of the water by evaporation. The starch and auxiliary polymer form the binding matrix of the sheets with the fibers and optional inorganic filler dispersed throughout the binding matrix. The starch-bound sheets can be cut, rolled, pressed, scored, perforated, folded, and glued to fashion articles from the sheets much like paper or paperboard. The sheets are particularly useful in the mass production of containers, such as food and beverage containers.
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Citations
75 Claims
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1. A method for manufacturing a starch-bound sheet comprising the steps of:
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(a) providing a starch-based mixture including water, initially ungelatinized starch granules, and an auxiliary water-dispersible organic polymer that is capable of reducing adhesion between the starch-based mixture and heated forming rollers upon gelatinization of the starch granules;
(b) forming the starch-based mixture into an initial green sheet by passing the mixture between at least one set of heated forming rollers having a temperature such that a portion of the auiliy water-dispersible organic polymer forms a layer of reduced adhesion on the outer surfaces of the initial green sheet in order to prevent substantial adhesion of the starch-based mixture to the forming rollers upon gelatinization of the starch granules;
(c) heating the initial green sheet to cause at least a portion of the starch granules to become gelatinized in order to form an intermediate green sheet; and
(d) removing at least a portion of the water from the intermediate green sheet by evaporation so as to form a starch-bound sheet having a binding matrix that includes a mixture of substantially dried starch and auxiliary water-dispersible organic polymer. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65)
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66. A method for manufacturing a starch-bound sheet comprising the steps of:
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(a) mixing together water, initially ungelatinized starch granules having a gelation temperature, and an auxiliary water-dipsersible organic polymer having a thermal precipitation temperature to form a starch-based mixture having a yield stress greater than about 200 Pa;
(b) forming the starch-based mixture into an initial green sheet by passing the mixture between at least one set of heated forming rollers having a temperature at or above the thermal precipitation temperature of the auxiliary water-dipsersible organic polymer such that a portion of the auxiliary water-dipsersible organic polymer forms a layer of reduced adhesion on the outer surfaces of the initial green sheet in order to prevent substantial adhesion of the starch-based mixture to the forming rollers upon gelatinization of the starch granules;
(c) passing the initial green sheet between at least one set of rollers having a temperature greater than the gelation temperature of the starch granules such that at least a portion of the starch granules become substantially gelatinized in order to form an intermediate green sheet; and
(d) contacting the intermediate green sheet with a heated drying roller in order to remove a substantial portion of the water from the intermediate green sheet by evaporation so as to form a sheet having a binding matrix including substantially dried starch and auxiliary water-dispersible organic polymer. - View Dependent Claims (67)
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68. A method for manufacturing a starch-bound sheet comprising the steps of:
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(a) mixing together water, substantially ungelatinized starch granules having a gelation temperature, an auxiliary water-dispersible organic polymer having a thermal precipitation temperature, fibers, and an inorganic filler to form a starch-based mixture having a yield stress greater than about 200 Pa and an inorganic filler concentration greater than about 10% by weight of total solids in the mixture;
(b) forming the starch-based mixture into an initial green sheet by passing the mixture between at least one set of heated forming rollers having a temperature at or above the thermal precipitation temperature of the auxiliary water-dipsersible organic polymer such that a portion of the auxiliary water-dipsersible organic polymer thermally precipitates on the outer surfaces of the initial green sheet in order to prevent substantial adhesion of the starch-based mixture to the forming rollers upon gelatinization of the starch granules;
(c) passing the initial green sheet between at least one set of rollers having a temperature greater than the gelation temperature of the starch granules such that at least a portion of the starch granules become substantially gelatinized in order to form an intermediate green sheet; and
(d) contacting the intermediate green sheet with a heated drying roller in order to remove a substantial portion of the water from the intermediate green sheet by evaporation so as to form a substantially hardened sheet having a binding matrix including substantially dried starch and auxiliary water-dispersible organic polymer. - View Dependent Claims (69)
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70. A method for manufacturing a starch-bound sheet comprising the steps of:
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(a) mixing together water, initially ungelatinized starch granules, an auxiliary water-dipsersible organic polymer, a fibrous material, and an inorganic aggregate filler to form a starch-based mixture; and
(b) forming the starch-based mixture into the starch-bound sheet by passing the mixture between at least one set of heated forming rollers having a temperature such that a portion of the an auxiliary water-dipsersible organic polymer forms a layer of reduced adhesion on the outer surfaces of the sheet upon gelatinization of the starch granules, in order to substantially gelatinize at least a portion of the starch granules, and in order remove a substantial portion of the water from the sheet by evaporation so as to form the starch-bound sheet having a binding matrix including substantially dried starch and auxiliary water-dipsersible organic polymer. - View Dependent Claims (71, 72, 73, 74, 75)
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Specification