GB2275051A

GB2275051A - Expanded starch balls

Info

Publication number: GB2275051A
Application number: GB9326237A
Authority: GB
Inventors: Osamu Chikazawa
Original assignee: Individual
Current assignee: Individual
Priority date: 1992-12-24
Filing date: 1993-12-23
Publication date: 1994-08-17
Also published as: DE4344219A1; GB9326237D0

Description

2275051 MOLDING MATERIAL, MOLDED COMPONENT, AND MANUFACTURING METHOD

Background of the Invention 1. Field of the Invention The present Invention is directed to a novel molding material, a molded component from the molding material and a manufacturing method for the material and the component, wherein each molding material, provided with proper elasticity and ease of molding, is manufactured of vegetable starch capable of being disposed by combustion or by water dissolving, and has a wide applicability in package cushioning, heat insulator, prototype mold of casting mold

lo and other area of applications. 2. Description of the Prior Art

Widely used as package cushioning for shipping Industrial products, such as home electronics and glassware, which may be easily damaged by external shock, are molded components, typicaUy of styrofoam, shaped to the geometry of a product or to granular pellets. Also widely used are cushioning and package molded from expandable resin other than expandable polystyrene. Also known is a cushioning material which is manufactured by heating and molding starch-based expandable material coated uith s,,-ntlietic 2 0 resin (Reference is made to Japanese Patent Application Publication No. S51-19399).

Most widely used package cushioning and package containers made of styrofbarn or other expandable resin are light-weight and robust and function as.a good cushioning material. When used packaging Is disposed by incinerating, however, It develops high temperature damaging an Incinerator, or it gives off toxic gases presenting pollution problems. Althrough the above quoted, starchbased expandable cushioning materials are readily disposed by incinerating, they still have synthetic resin coating which may still be a source of pollution when Incinerated. Disposal by water dissolving is far from applicable in these materials.

lo Surnmajy of the Invention In view of the above problems, the present Invention has been developed. It is the object of the present Invention to provide a molded component such as package cushioning or heat insulator, which develops neither high temperature nor toxic gases, and which is light-weight, pollution-free and water soluble enough to be drained away with water or to be disposed underground.

To achieve the above object, in the method of the present invention, fine starch powder extracted from one or more plants selected frem the group consisting of cassava, corn, wheat, potato, arrowroot, sago and the like Is formed into granulated starch, the granulated starch is subjected to heating, pressurization and then rapid depressurization in order to expand it to numerous starch balls, and the starch balls are used as they are, or are shaped into planar or other arbitrary configurations by pressurization and then 2 5 adhesion.

2 Since the starch balls resulting from depressurization and expansion are light-weight and adequately elastic, they may be used as padding for cushioning. or they may be shaped into a desired form to be used as package cushioning. Without having to use adhesive, such as synthetic resin adhesive, the shaping is performed by moistening the surface of starch balls to allow the surface of starch balls to absorb moisture and then gelatinize, by pressurizing gelatinized starch balls in the cold, and by allowing them to adhere to one another in a mold. The method thus easily results in a molded component of a desired shape.

Since the starch balls are made of pure vegetable starch, the incineration of used starch balls develops neither high temperature nor toxic emissions. The starch balls are highly soluble. and instantly dissolves In water. When disposed underground, the starch is balls naturally decay and are consequently reduced to soils. In both cases, a pollution-free disposal Is thus achieved.

Since the Molding material according to the present Invention is made by heating and pressurizing starch powder such as tapioca, which is 100% vegetable starch, and then depressurizing to allow starch to expand to starch balls, each resulting starch ball Is lightweight and adequately elastic, and offers ease of molding. The starch balls offer not only a mechanical strength sufficient enough to work as package cushioning, but also an excellent moisture-absorption characteristic which prevents condensation when used as a heat insulator, compared with a conventional shrofoam.

Since the molded component described above, if coated with zein, exhibits excellent water repellency and excellent water resistance, it finds manv apfflications such as a shipping container for fresh vegetable or a general-purpose food container.

A molded component lined internally with zein film works as an excellent air barrier, and enhances cushioning characteristics If used as package cushioning. On the other hand, the component, as it is, may be outperformed by other types of molded components in terms of dissolving speed. If the component is disposed in water with lo its zein film, destroyed, undissolved composition including zein film in the form of organic matter becomes 100% biodegradable, activated sludge which can be digested or dissolved by bacteria and other microbes. Thus, when disposed, the component gives ofr no pollutant which may be damaging to sewer systems, purification plants and river systems. When incinerated, the component develops neither abnormally high temperature nor toxic gases. Thus, the molding material and the molded component from the material, according to the principle of the present Invention, are useful and novel in that the used molded component is disposed in an easy and pollution-free manner.

Brief Desc9Rtion of the Drawings Fig. 1 Is the essential process flow chart of starch balls according to the present invention.

Fig. 2 Is another process flow chart of starch balls according to the present invention.

Fig. 3 is a diagrammatic view of an example of a mold for the molding material according to the present invention. Detailed Description of the Preferred Embodiment In the following description of embodiments 1 and 2 of the present Invention, the process of starch balls which constitute one of the molding materials according to the present invention, is exemplified only by tapioca known as starch extracted from cassava roots for human consumption or for animal feeding, for simplicity of explanation. The present invention is also applicable to starch 1 derived from other type of plants.

[Embodiment 1 for the process of starch bail] Fig. 1 is the essential process flow chart of starch balls. Tapioca used here as a molding material Is extracted from cassava roots and then processed into fine starch powder. The term granulated tapioca means In the context of the present Invention the one which is manufactured by mixing the tapioca with added water to make it pasty, passing the paste of tapioca through fine mesh, then allowing it to fall onto an iron plate heated up to 120 to 15TC and to roll over the heated iron plate to result In dried 2 0 granular pellets having a diameter of 1 to 5 mm.

The granulated tapioca is placed in a drying rotary pressure boiler with an adequate Internal volume in a manner that 30 to 70% of the Internal volume of the boiler occupied by the granulated tapioca. The boiler is then sealed and rotated while being heated.

2 5 When the inner pressure of the rotary boiler reaches 8 to 10 atmospheres, the heating and rotation are stopped, and the lid of the rotary boiler keeping the rotary boiler sealed Is then quickly and fully opened at a time. The depressurization of the boiler immediately taking place In succession to the release of the lid allows the granulated tapioca to expand five to 10 times in volume to starch balls having a diameter of 2 to 15 mm.

To prevent each tapioca granule from sticking to the other in the course of heating and pressurizing, the Interior of the boiler requires to be kept diy. Furthermore, a weight of three to five grams of fine powder of zeolite, calcium bicarbonate, or an Inorganic mineral is preferably added to each kilogram of the granulated tapioca placed Inside the boiler. [Embodiment 2 for the process of starch balls] Fig. 2 is another process flow chart of starch balls according to the present Invention. Shown In the figure are a hopper 1, a wet-type grain expander 2, and an extrusion nozzle 3 connected to the grain expander 2. The bore diameter of the extrusion nozzle is 1 to 5 mm. The cross section of the extrusion nozzle bore may be typically circular or polygonal, though it may be optionally set to any other shape. The nozzle may be an array of bores opened to Its end rather than a single bore only.

The granulated tapioca processed as already described is Introduced Into the hopper 1, and pressurized while being subjecting to the mixing by the wet-type grain expander 2 under high temperature and moistened conditions In order to deliver the pressurized paste of mixed tapioca through the nozzle 3. When depressurized as a result of exposure to the ambient out of the passage of the nozzle, the well-mixed tapioca rapidly expand 2 to 5 times the bore diameter of the nozzle. The bar-like tapioca extruded continuously is cut by a rotary cutter 4 into pellets, and then they are dried as starch balls.

The bar-like tapioca which Is extruded, then depressurized and expanded as described above, may be cut to pellets of which length is almost the same size as their diameter. Alternatively, the bar-like tapioca may be cut to pellets of which length is twice as long as or longer than their diameter.

In the above embodiments, a weight of 1 kg of granulated tapioca resulted in an overall volume of 8 to 15 liters of starch balls. In each of the above embodiments, the starting material is 100% tapioca powder. Alternatively, tapioca powder may be blended with maize powder of 5 to 30% by weight.

Since starch bafis processed as in the embodiments 1 and 2 are lightweight and adequately elastic, they are directly used as package cushion as they are. Furthermore, It is optional to place starch balls into halves of a mold or into each of adequately divided partitions of the mold that matches the outer configuration of a product to be packaged, and then to allow the starch balls to be pressurized and molded under a moistened condition to be applied as package cushioning. It is further optional to mold starch balls into planar configuration to be used as heat insulator or sound insulating material, or Into any desired configuration to be used as a prototype mold of a casting mold.

Known in the prior art is that a highly elastic product is obtained by blending a relatively large quantity of amylose, which is one of the major compositions constituting granulated starch, Into a material to be expanded. In the present invention, if high elasticity is required of a molded component, like the one for package cushioning, tapioca is blended with high amylose starch which has an amylose content of 30% or more before the blended starch is expanded. The starch balls thus produced match conventional expandable polystyrene in terms of recovering elasticity and compression properties.

Discussed next Is a molding method embodied in the following three examples in which the above-described starch balls are molded on the mold shown in Fig. 3. [Embodiment 1 for molded component] A fixed amount of starch balls 5 held in the hopper 10 is transferred by means of forced air feeding or the like into a female mold 7 with its male half 6 in a recessed position; steam which is generated from extracellular enzyme amylase dissolved water held in the tank of a room-temperature or low-temperature humidifier (not shown) is let into the mold through an inlet pipe 8 and then let out through an outlet pipe 9; the steam Is In contact with the surface of starch balls 5 while it passes through the inside of the mold from the Inlet pipe 8 to the outlet pipe 9 and adequately moistens the surface of starch balls 5; and starch on the surface of the starch balls gelatinizes, thereby becoming adhesive. Instead of roomtemperature or low- temperaure steam. high -temperature heated steam (superheated steam) with 20 to 30% moisture content may be used to adequately moisten the surface of starch balls and then to gelatinize them. Such an option falls within the scope of the present invention.

The male half 6 Is moved toward the female mold 7 by a predetermined stroke to apply pressure to the starch balls. The starch balls are pressed with one another along the Inner surface of the mold, and then remain adhered to one another. The inlet pipe 8 is now used to let warm dry air or hot dry air in to dry the compressed starch balls, and the molded component is released from the mold. As an alternative to the drying process In which the inlet pipe 8 is used to let warm air or hot air In, the inlet pipe 8 or another pipe provided separately may be used to evacuate air and moisture from Inside the mold to make the Interior of the mold semi-vacuum and consequently to dry the compressed starch balls. Alternatively. the moisture of the compressed starch balls may be 2 0 evaporated by microwave to dry the starch balls. -[Embodiment 2 for molded component) A fixed amount of starch balls cooled down to approxiinately O'C is fed directly or fed via the hopper 10 Into the mold. In the course of feeding. the starch balls are exposed to room-temperature ambient air and then to room - temperature, moistened air inside the mold. The humidity difference between both airs causes condensation the surface of each starch ball. Condensation allows the starch balls to be adequately moistened and then to gelatinize. The rest of the process of molding, drying and releasing, that follows thereafter remain unchanged from those described in the embodiment 1. The component matching the mold in use Is thus obtained. [Embodiment 3 for molded component] In this manufacturing method, alcohol having a purity of 80 lo to 90% (with moisture content of 10 to 20%) is applied via the inlet pipe 8 to starch balls 5 which have already been fed directly or fed via a hopper 1 into a mold. When alcohol is well distributed on the surface of each starch ball, the male half 6 is manipulated to pressurize and mold the starch bans.

Moisture content of the alcohol is evenly distributed on the surface of each starch ball allowing each starch ball to wet and gelatinize, warm or hot air is let in via the inlet pipe 8 at the moment the male half 6 finishes Its action for molding, in order to allow alcohol to volatize, and the resulting molded component is released from the mold.

The addition of crystalline amylase to water held In the tank of the humidifier in the above embodiment 1 or to the water-containing alcohol solution in the above embodiment 2, expedites the gelatinization of the surface of starch balls by means of hydrolytic action of arpylase. This enhances adhesion of the starch balls, thereby facilitating molding process. Removal of moisture content In the course of drying process of the molded component stops amylase action or hydrolytic action, and a desired molded component is obtained.

In this case, j? -amylase expedites the hydrolytic action of starch, in which two major compositions of starch, amylopectin and amylose, play a major role. Since both compositions have different rates of hydrolytic action, setting a proper ratio of arnylopectin to arnylose achieves desired adhesion.

In each molding method discussed above, if the inner surface of the mold is sufficiently heated in advance, a resulting molded component is not only provided with an excellent surface smoothness, but also easily released from the mold when molding operation is completed.

In other aspect, the molded component thus manufactured has a watersolubility. If It Is put Into contact with moisture content while It is In use as packaging or food containers, the component may partially dissolve leading deformation and destruction. To prevent such a thing, the surface of each starch ball or the surface of a molded component is preferably coated with zein which is water resistant resin.

The terin zein in the context of the present invention refers to a maize-derived, organic-solvent soluble protein which has been developed and disclosed by the National Food Research Institute of Japan's -Ministry of Agriculture, Forest-nand Fishery. A solvent medium and film-forming conditions known to work are as follows: zein is dissolved into an acetone solution with a 30% water content to obtain a zein solution, and under a WC atmosphere with a 50% humidity the., the zein solution Is applied to the starch balls and then allowed to dry and thus transparent and high water-resistance zein film is formed on the starch balls.

The zein film of 60 Lt m thus formed has a pore-resisting strength of 700 g and Its water permeability is approximately 40 micro-liter for 20 hours. The zein film is known to work as a heat 10 sealer because it easily melts when heated.

Since the zein film has heat melt characteristic as described above, starch balls, each having zein coating, are easily heat-molded without having to gelatinize the surface of each starch ball as described in the above embodiment.

f What Is claimed is.

1. A molding material made of a number of starch balls, wherein a refined starch powder is formed into granulated starch through granulation process, and said granulated starch Is expanded through a series of processes of heating, pressurizing, and then rapid depressurizing, resulting In said starch balls.

2. A method for manufacturing a molding material, wherein a refined starch powder is formed Into granulated starch through granulation process, and said granulated starch is subjected to a series of processes of heating, pressurizing, and then rapid depressurizing, resulting in said molding material.

3. The molding material according to claim 1, wherein said refined starch powder is derived from one or more selected from the group consisting of cassava, corn, wheat, potatoes, arrowroots and sago.

4. The molding material according to claim 1. wherein said granulated starch Is granulated tapioca, whereby said granulated tapioca is manufactured by adding water to and then mixing the tapioca powder derived from cassava roots so that It becomes the paste of tapioca, then by passing the paste of tapioca through a fine mesh, then by allowing said paste to fall onto an Iron plate heated up to 120 to 1500C and to roll on the heated iron plate. thereby resulting in dried granular pellets having a diameter of 1 to 5 mm.

5. The molding material according to claim 1, wherein said granulated starch is made of tapioca blended with maize powder of 5 to 30% by weight.

6. The method for manufacturing the molding material according to claim 4, wherein said method comprising the steps of placing said granulated tapioca in a drying rotary pressure boiler in a manner that 30 to 70% of the internal volume of the boiler occupied by the granulated tapioca, sealing and then rotating the boiler while being heated and pressurized, stopping the rotating and heating of the boiler when the inner pressure of the boiler reaches 8 to 10 atmospheres, and releasing the boiler by quickly and fully lo opening the lid of the boiler at a time.

7. The method for manufacturing a molding material comprising the steps of introducing granulated tapioca into a hopper, pressurizing said granulated tapioca while subjecting said granulated tapioca to the mixing by a wet-type grain expander under a high temperature and moistened condition in order to deliver the pressurized paste of tapioca through a nozzle, allowing the paste of tapioca to rapidly expand at the nozzle as a result of depressurization, cutting the bar-like tapioca paste that Is continuously extruded from the nozzle into starch balls, by means of a rotary cutter, and then drying said starch balls.

8. An apparatus for manufacturing a molding material, comprising a hopper to which granulated tapioca is introduced, a wet-type grain expander for pressurizing said granulated tapioca while Mixing said granulated tapioca under a high temperature and 2 5 moistened condition, and an extrusion nozzle for extruding continuously said mixed tapioca while allowing said mixed tapioca rapidly expand as a result of depressurization.

9. The method for manufacturing the molding material according to claim 6, wherein a fine powder of an inorganic mineral such as zeolite or calcium bicarbonate is added to tapioca held In said boiler.

10. The molding material according to claim 1, wherein said refined starch powder is blended with arnylose of 30% or more by weight.

11. A molding material obtained by coating with zein the surface of each of or a group of the molding material according to claim 1.

12. A molded component obtained by moistening and gelatinizing the surface of the molding material according claim 1, and then by pressurizing the molding materials to be adhered to one another inside a desired mold so that said materials are shaped into an arbitrary geometry such as a planar geometry.

13. A molded component obtained by heating and pressurizing a number of the niolding materials according to claim 11 to make said molding materials to be adhered to one another so that said molding materials are shaped into an arbitrary geometry such as a planar geometry.

14. A method for manufacturing a molded component comprising the filling step In which a mold is filled with a fixed amount of the molding material according to claim 1 with a male - is - half In a recessed position, the gelatinizing step In which the surface of each of said molding material Is gelatinized by moistening the surface of each of said molding material, the molding step In which the molding materials are pressurized by driving the male half by a predetermined amount of travel to press the molding materials into the mold and to allow the molding materials to adhere to one another, and the drying step in which the molded component inside the mold is dried.

15. The method for manufacturing a molded component lo according to claim 14, wherein said gelatinizing step for the surface of each molding material is performed using steam resulting from a room-temperature or low-temperature humidifier.

16. The method for manufacturing a molded component according to claim 15, wherein said steam is derived from water Into which amylase, a type of extracellular enzymes, is dissolved.

17. The method for manufacturing a molded component according to claim 14, wherein said gelatinizing step for the surface of each molding material is performed using high temperature heated steam ( superheated steam) with moisture content of 20 to 30%.

18. The method for manufacturing a molded component according to claim 14, wherein said gelatinizing step for the surface of each molding material is performed by exposing a fixed amount of starch balls that are cooled in advance to high humidity air in order to allow condensation to develop on the surface of the starch balls.

19. The method for manufacturing a molded component according to claim 14, wherein said gelatinizing step for the surface of each molding material is performed by applying alcohol of 80 to 90% purity to the starch balls held in the rnold, activating the male half to pressurize and mold, and then letting warm or hot air in into 5 the mold to cause said alcohol to volatize.

20. The method for manufacturing a molded component according to claim 14, wherein said drying step for the molded component is performed by letting warm dry or hot dry air in into the mold.

2 1. The method for manufacturing a molded component according to claim 1-4, wherein said drying step for the molded component is performed by evacuating hun-dd air from Inside the mold to result In a semi-vacuum condition In the mold. 22. The method for manufacturing a molded component according to claim 14, wherein said drying step for the molded component is performed by evaporating moisture content by means of microwave heating.