Molded fiber manufacturing

Abstract

Molded fiber products using agriculture residues are economical and environmentally beneficial. Molded fiber manufacturing is different from molded pulp. The present invention discloses a method of and an apparatus for the manufacturing of molded fiber shaped body (10) using low consistency fiber slurry (12) subject to vacuum-forming and thermo-curing. The use of porous material as mold inserts for both vacuum-forming (101) and thermo-curing (102) stations provides improved productivity and enables ease of mold release. The incorporation of self-cleaning techniques further ensures consistent performance of the manufacturing system.

Description

[0001] This invention relates to a method of and an apparatus for improving the manufacturing of molded fiber shaped body. BACKGROUND [0002] Products made of molded fiber are environmental friendly. Raw materials for manufacturing molded fiber products are derived from agriculture residues which are usually treated as waste. Unlike pulp, fibers from agriculture residues do not need to be rigorously treated before they are used. When molded fiber products are disposed, they are biodegradable and are emission neutral. [0003] Molded fiber shaped bodies can be used as packaging for food, industrial goods, consumer products and many others. It has very good cushioning property and is ready to be used without the need to cut, bend and fold. It is also light and stackable which reduce storage and shipping space. Molded fiber packaging is a cost economical and environmental friendly choice to replace existing plastics and paper packaging. [0004] Vacuum thermoforming method using low-consist...

AI Technical Summary

Benefits of technology

[0014] It is an objective of the present invention to increase the productivity of manufacturing molded fiber shaped bodies. Porous materials fabricated into the desired shape are used as mold inserts in the vacuum-forming molds and the thermo-curing molds to eliminate the use of sieves. As a result, production downtime is reduced as there is no longer a need to maintain and change sieves on the vacuum-forming and thermo-curing molds. With the use of porous material as mold inserts in the vacuum-forming process, a uniform layer of wet fiber is deposited on the porous mold inserts after the application of vacuum to draw fluid away from the slurry. The porous mold insert redistributes the vacuum force evenly over its entire surface. The porous mold inserts have open and interconnected pores to allow fluids and air to pass through from one surface to another. The pore size of the porous mold insert range between 5 micrometer to 200 micrometer depending on the size distribution of the fiber material. It is preferred that the pore size is smaller than the smallest fiber size in order not to cause blockage to the pore channels.

[0016] Yet another objective of the invention is to reduce the energy consumption in manufacturing molded fiber shaped body. Most of the energy is consumed in the thermo-curing process where large amount of thermal energy is used to dry excessive water in the wet fiber shaped body. It is understood that reducing the amount of water in the wet fiber shaped body will reduce the thermal energy. The present invention optimize the use of mechanical dewatering means to reduce the water content in the wet fiber shaped body formed by the vacuum-forming process. The vacuum-forming process uses a pair of matching molds namely top and bottom molds. The top and bottom molds are opened to allow the fiber slurry to be added. Water in the fiber slurry is extracted away by vacuum means through the porous mold inserts to form a uniform layer of wet fiber shaped body on the bottom mold. In order to extract more water out of the wet fiber shaped body, the top mold and bottom mold are closed and sealed to prevent air infiltration during vacuum dewatering of the wet fiber shaped body. Simultaneously, the top mold and bottom molds apply a slight pressure to the wet fiber shaped body. The mechanical dewatering process stops when the water content in the wet fiber shaped body reaches some pre-determined level, usually in the range of 20% to 50% (wt). It is to be noted that if the top and bottom molds are not sealed when closed, vacuum dewatering will not be effective as ambient air instead of water in the wet fiber shaped body will be extracted.

[0017] Yet another objective of the present invention is to reduce maintenance by incorporating built-in self-cleaning means for the porous mold inserts. The self-cleaning means include the use of ultrasonic transducers and back-flushing. The vacuum-forming porous mold inserts are susceptible to clog due to fibers entrapped in the pores. Clogged vacuum-forming mold inserts will affect molded fiber shaped body uniformity and increase energy consumption. Eventually, the clogged vacuum-forming mold inserts will cease to function. According to the present invention, the vacuum-forming mold inserts are cleaned with ultrasonic meaning and back flushing.

Problems solved by technology

The air pockets reduce the adhesion of the molded fiber shaped body to the thermo-curing mold.

It is to be noted that if the top and bottom molds are not sealed when closed, vacuum dewatering will not be effective as ambient air instead of water in the wet fiber shaped body will be extracted.

Images