Abstract
The present invention provides a moldable mixture containing large portion of agricultural fibers and small portion of a binding agent and a flow-promoting filler material. The moldable mixture is substantially free of formaldehyde, with low moisture content and high draw ratio. The present invention also provides methods of manufacturing molded products and related parts, based on the claimed moldable mixture. Molded products (830) and related parts such as runner (810) and plank (820) with light weight, high density and more complex profile are manufactured by the claimed methods including steps of providing required materials for a moldable mixture, mixing the provided materials to form a moldable mixture, shaking the moldable mixture in preparing for compression molding and compression molding the moldable mixture to form molded products and related parts.
Claims
1.-20. (canceled)
21. A pallet comprising: a molded material comprising greater than 0% and no more than 5% by weight of a binding agent, greater than 0% and no more than 10% by weight of a flow-promoting filler material, and 85% to 95% by weight of at least one agricultural fiber, wherein the molded material is free from any hardeners, impact modifiers, a co-solvents or a de-molding agents, wherein the binding agent consists of diisocyanate-diphenylmethane, wherein said agricultural fiber consists of at least one agricultural fiber having a hollow core, trimmed to a length from 5 millimeters (mm) to 10 mm, and has a moisture content of greater than 0% and less than 8%, and wherein said agricultural fiber is selected from a group consisting of rape straw and rice stalk, or a combination thereof, wherein said flow-promoting filler material is wheat flour, and wherein the pallet did not undergo any form of post-heat treatment or fumigation.
22. A molded product comprising: greater than 0% and no more than 5% by weight of a binding agent, greater than 0% and no more than 10% by weight of a flow-promoting filler material, and 85% to 95% by weight of at least one agricultural fiber, wherein the molded material is free from any hardeners, impact modifiers, a co-solvents or a de-molding agents, wherein the binding agent consists of diisocyanate-diphenylmethane, wherein said agricultural fiber consists of at least one agricultural fiber having a hollow core, trimmed to a length from 5 millimeters (mm) to 10 mm, and has a moisture content of greater than 0% and less than 8%, and wherein said agricultural fiber is selected from a group consisting of rape straw and rice stalk, or a combination thereof, wherein said flow-promoting filler material is wheat flour, and wherein the molded product did not undergo any form of post-heat treatment or fumigation.
23. The pallet of claim 21, wherein said agricultural fiber has a moisture content of greater than 0% less than 5% by weight to said moldable mixture.
24. The moldable product of claim 22, wherein said agricultural fiber has a moisture content of greater than 0% less than 5% by weight to said moldable mixture.
25. The pallet of claim 21, wherein the moldable material was formed under a pressure of 0.30 to 0.40 kg/mm.sup.2.
26. The moldable product of claim 22, wherein the moldable product was formed under a pressure of 0.30 to 0.40 kg/mm.sup.2.
27. The pallet of claim 25, wherein the moldable material was formed under a single compression stroke.
28. The moldable product of claim 26, wherein the moldable material was formed under a single compression stroke.
29. The pallet of claim 21, wherein the moldable material has a draw ratio 10.
30. The moldable product of claim 22, wherein the moldable material has a draw ratio 10.
Description
BRIEF DESCRIPTION OF THE FIGURE
[0019] FIG. 1 shows the flow chart of manufacturing a close-molded product.
[0020] FIG. 2 is an illustration of a device for shaking the moldable mixture throughout the discharging of the moldable mixture from IBC until loading the moldable mixture into a mold.
[0021] FIG. 3 shows the top and bottom views of the material feeding tray used in the shaking step.
[0022] FIG. 4 is an enlarged image of the material feeding tray showing an additional vibrator in each corner for shaking the moldable mixture during the shaking step.
[0023] FIG. 5 shows the design of the material feeding tray with shaking features in the present invention (lower part) for loading the moldable mixture to the bottom mold at the pressing area as compared to the design of the conventional material feeding tray (upper part) without shaking features.
[0024] FIG. 6 is an enlarged image of the mold and the hydraulic press at the pressing area in the molding step.
[0025] FIG. 7 shows the cross-section of the top and bottom mold with the moldable mixture before and after compression in the molding step.
[0026] FIG. 8 shows the side-prospective view of a molded pallet of the present invention.
DETAILED DESCRIPTION OF INVENTION
[0027] In FIG. 1, the claimed methods of manufacturing molded products and related parts are mainly arrived by four steps including a providing step (100), a mixing step (120), a shaking step (140) and a compression molding step (160). In the providing step, agricultural fibers provided to form a moldable mixture may be rape straw, rice stalk or a combination of both. In one embodiment, the raw materials of agricultural fiber have to be trimmed to a length ranges from 5 to 10 mm in a trimming step (not shown) prior to mixing with other components to form a moldable mixture. The trimmed raw agricultural fibers are then dried in a drying step (not shown) to have less than 8% moisture content to the total weight of the moldable mixture, preferably have less than 5% moisture content to the total weight of the moldable mixture. The drying step of the raw materials of the agricultural fiber is followed by a weighing step (not shown) to weigh a suitable amount of substantially dry agricultural fiber prior to mixing with other components to form the moldable mixture. In one embodiment, the percentage by weight of the substantially dry agricultural fiber is between 85%-95% to the total weight of the moldable mixture. In the providing step, a binding agent is also provided to form the moldable mixture. In one embodiment, the binding agent is Diisocyanate-diphenylmethane (MDI). Alternatively, the binding agent can be any soy-based binding agent. In one embodiment, soy-based binding agent used in the moldable mixture may be soy flour. The percentage by weight of the binding agent is not more than 5% to the total weight of the moldable mixture. This binding agent is high viscosity, low in moisture content and free of formaldehyde. In the providing step, a flow-promoting filler material is also provided to form the moldable mixture. In one embodiment, the flow-promoting filler material is wheat flour. The flow-promoting filler material is less than 10% by weight to the moldable mixture. In a preferred embodiment, three main materials including agricultural fibers, a binding agent and a flow-promoting filler material are provided in the providing step to form a moldable mixture, but hardening agent, impact modifier, co-solvent and a de-molding agent are not provided in the same providing step. In one embodiment, hardener such as ammonium chloride, de-molding agent such as soya extract, co-solvent such as alcohol, and impact modifier such as palm fibers are not provided in the providing step to form a moldable mixture.
[0028] In FIG. 1, after weighing the substantially dry agricultural fiber in a weighing step (not shown), 85%-95% by weight of the substantially dry agricultural fiber such as rape straw, rice stalk or a combination of rape straw and rice stalk is mixed with other components to form a moldable mixture in a mixing step (120). In one embodiment, the mixing step is a two-step mixing step. In the first part of the two-step mixing step, 85%-95% by weight of the substantially dry agricultural fiber is mixed with less than 10% by weight of a flow-promoting filler material such as wheat flour in a mixing machine (not shown). In one embodiment, the mixing machine comes with a horizontal rotating blade (#4 blades mounted on horizontal shaft) and it is rotating at about 20 to 30 rpm. While the agricultural fiber is stirred in the mixing machine, the wheat flour of less than 10% by weight is introduced to the stirring agricultural fiber in the first part of two-step mixing step. In the second part of the two-step mixing step, not more than 5% by weight of a binding agent such as Diisocyanate-diphenylmethane (MDI) or any soy-based binding agent is also introduced to the mixing machine by spraying (not shown). In one embodiment, not more than 5% by weight of MDI is sprayed with a pressure nozzle at a pressure of around 5 to 8 bars into the stirring mixture of agricultural fibers and a flow-promoting filler material. In another embodiment, not more than 5% by weight of soy-based binding agent such as soy flour is sprayed with a pressure nozzle at a pressure of around 5 to 8 bars into the stirring mixture of agricultural fibers and a flow-promoting filler material. In the mixing step, the mixture of agricultural fibers, a flow-promoting filler material and a binding agent is kept stirring until such mixture is blended to form a moldable mixture. In one embodiment, the whole rotating cycle for a mixing step takes less than 3 minutes.
[0029] In FIG. 1, upon completion of the mixing step (120), the moldable mixture is ready for feeding the moldable mixture to the mold in a shaking step (140). In the shaking step, the moldable mixture is loaded into an Intermediate Bulk Container (IBC) (not shown) and then discharged through the weighing Hopper (not shown) into a material feeding tray at the material loading station (not shown). The material feeding tray filled with moldable mixture is then transferred from the material loading station to a pressing area (not shown) where compression molding (160) takes place. In one embodiment, the moldable mixture has been shaking throughout the discharging of the moldable mixture from IBC through the weighing hoop into the material feeding tray. In another embodiment, the material feeding tray containing the moldable mixture has also been shaking throughout the loading of the moldable mixture from the material feeding tray to the cavity of the bottom mold at the pressing area where compression molding takes place.
[0030] In FIG. 1, after shaking (140) the moldable mixture, the moldable mixture is ready for being compressed in a compression molding step (160). The compression molding step is performed at a single compression stroke. In one embodiment, the compression molding step is carried out at a temperature between 200-230° C. In one embodiment, the mold is heated up through internal heat transfer at a temperature between 200-230° C. The moldable mixture is compressed under a pressure between 0.30 to 0.40 kg/mm.sup.2 for 1.5 to 2.5 minutes. After compression molding, the molded product is ejected out from the mold and then transferred to a packing area next to the pressing area. The molded product is not subjected to heat treatment and fumigation for killing any living pests after ejecting out from the mold.
[0031] An example of mixing and shaking the moldable mixture is given in FIG. 2. In this example, the Intermediate Bulk Container (IBC) (81) is placed at the top of a stand-alone material loading station (85). The moldable mixture (not shown) may be discharged through a discharging screw (not shown) into a weighing hopper (82) and then further discharged into a material feeding tray (83) in a row-by-row manner. After the completion of the discharging, the material feeding tray is then transferred along the tray movement path (84) to the pressing area (88) where the compression molding step takes place. The moldable mixture being transferred into the mold (87) at the pressing area is compressed by the hydraulic press (86) into the molded product.
[0032] An example of a material feeding tray is given in FIG. 3. In this example, the top view of the material feeding tray (310) shows that it may have an average size of 1.4×1.2×0.2 meter (Length×width×height) and may be divided into 35 to 49 compartments to cater for the loading of different weight of moldable mixture for molding into product with different profile and thickness at different part of the product. Each compartment (320) is designed to take different weight of moldable mixture. This is to ensure that the right amount of the moldable mixture is loaded evenly into the mold at the pre-determined position for optimum molding result and material utilization. It also helps to facilitate the molding process to provide with the maximum draw ratio and enables to mold products with different profile and thickness at different sections of the product. The combination of compartments varies from the complexity and the size of the molded product. In order to facilitate the flowing of the agricultural fibers in a mold during the molding step, the partitions of the material feeding tray are constructed by steel sheet (not shown) in a criss cross manner to form the necessary compartments.
[0033] The example as given in FIG. 3 shows that the bottom view of the material feeding tray has a piece of wire mess (330) welded at the bottom face of the steel partitions. The entire steel partition is connected to a rotating rod with a vibrator mounted (not shown). The steel partition together with the welded wire mess can be used for shaking in the horizontal direction throughout the discharging of the moldable mixture, from the material feeding tray to the mold at the pressing area (not shown). The gate (340) mounted at the bottom of the material feeding tray is then opened by sliding movement in the horizontal direction when the material feeding tray is transferred to the mold at the pressing area.
[0034] On top of the welded wire mesh, four additional vibrators (410) as shown in FIG. 4 are mounted at the four corners of the material feeding tray which are also shaking concurrently in the vertical direction throughout the discharging and loading of the moldable mixture.
[0035] In the lower part of FIG. 5, the moldable mixture (530) is discharged into the cavity of the bottom mold (560) in an evenly dispersed manner with the aid of both the horizontal and vertical vibration motions generated by the rotating rod with a vibrator (not shown in FIG. 5) and four additional vibrators at four corners of the material feeding tray (550) as described above prior to the compression molding step. This kind of shaking feature is incorporated in the present invention due to the fact that when using the conventional method, the loading of moldable mixture from the conventional material feeding tray (510) into the bottom mold without any shaking always forms a hump (520). On the other hand, the material feeding (540) of the present invention has to be leveled by four additional vibrators at four corners of the bottom side (550) to enable shaking when loading the moldable mixture from the material feeding tray into the bottom mold at the pressing area. Such feature can achieve the effect of optimum molding results, i.e. minimum molding pressure, minimum material use. Such feature also enables the moldable mixture to flow freely to the desired height which can be determined by the draw ratio. After the moldable mixture is fully loaded into the cavity of the bottom mold, the material feeding tray may be returned to the original position for re-filling.
[0036] An illustration of a hydraulic ejection system for molding is given in FIG. 6. In this example, the hydraulic ejectors (630) are situated below the bottom mold at the pressing area. In one embodiment, the moldable mixture is molded at a pressing area at a temperature between 200-230° C. Both the top (610) and bottom (620) mold are fitted with various steel pipes (not shown). The thermal oil is electrically heated and circulating through the oil channels inside the mold. Since the mold is heated up through heat transfer within the mold, therefore it can achieve a lower energy loss.
[0037] In one embodiment, the moldable mixture is compressed under a pressure between 0.30 to 0.40 kg/mm.sup.2 for 1.5 to 2.5 minutes at the pressing area. The compression molding is performed as a single compression stroke. There is no need to open and close the mold repeatedly nor ironing to release excess moisture to prevent possible mold explosion because the moldable mixture of the present invention has relatively low moisture content. After the compression, the molded part is ejected out from the bottom mold with the hydraulic system (630). A mechanical pick and place system (not shown) is incorporated in the material feeding system to pick up the molded part and transfer the molded part to a packing area (not shown) next to the pressing area. Since the molded product has been subjected to high heat and high pressure during the molding process, further heating and fumigation steps for killing living pests in the molded product are not required.
[0038] FIG. 7 illustrates the cross-section of a molding part in the mold before and after the compression in the molding step. The upper part of the figure shows the cross-section of the moldable mixture (720) in the cavity of bottom mold (740) before the compression molding step whereas the lower part of the figure shows the cross-section of part of the molded product (760) in the cavity between the top mold (780) and the lower mold (790) after the compression molding step. In one embodiment, the top mold (780) is pressed on the moldable mixture in the cavity of the bottom mold (790) with a pressure of 0.30 to 0.40 kg/mm.sup.2 to form molded product (760). The compression molding for the moldable mixture into part of a molded product is a single compression stroke without the needs of opening and closing the mold repeatedly. In one embodiment, the moldable mixture after the compression flows upwards towards the horizontal molding cavity of the enclosed mold under the temperature between 200-230° C. The height (750) of part of the molded product (760) along the horizontal molded cavity of the enclosed mold can be determined. The draw ratio of the moldable mixture is obtained from dividing the height (750) of the molded part (760) in the horizontal molding cavity of the enclosed mold after compression by the height (710) of moldable mixture (720) in the cavity of bottom mold (740) before compression. Such ratio reflects the upwards flowing ability of the moldable mixture during molding.
[0039] Due to the high draw ratio and high density, the molded part can be corrugated with complex profile such as runner (810) and plank (820) of a pallet (830) as shown in FIG. 8. The molded product is ready for use or can be used repeatedly without any post-heat treatment and fumigation.
[0040] While the present invention has been described with examples to preferred embodiments, it will be apparent that other changes and modifications could be made by one skilled in the art, without varying from the scope or spirit of the claims appended hereto.
INDUSTRIAL APPLICABILITY
[0041] The present invention provides a moldable mixture and methods of manufacturing molded products and related parts based on the claimed moldable mixture. The claimed moldable mixture can be applied to the field of construction materials and manufacture of molded products such as pallets and related parts. The claimed methods of manufacturing can be applied to making construction products or molded products with better quality.
