Plastic and nonmetallic article shaping or treating: processes – Forming articles by uniting randomly associated particles – Stratified or layered articles
Reexamination Certificate
1999-05-10
2001-10-23
Theisen, Mary Lynn (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Forming articles by uniting randomly associated particles
Stratified or layered articles
C264S109000, C264S115000
Reexamination Certificate
active
06306324
ABSTRACT:
BACKGROUND OF INVENTION
1. Field of Invention
The present invention relates to a method for manufacturing packaging material and sheets, particularly to a method for manufacturing disposable food and beverage containers and seedling-breeding containers by using plant straws.
2. Concise Explanation of Prior Art
CN 1130559 discloses a method for manufacturing disposable sanitary food containers by using straws, including pulverizing non-toxic straw into powder; mixing the powder with a binder, putting the mixture into a mold to produce a semi-product, and then coating the semi-product with a water-repellent agent on its surfaces, wherein, the weight ratios of straw powder, binder and water-repellent agent are 70-75%, 22-25% and 2-5% respectively. But in practice, it is found that it is not advantageous to use high percentage of binder because of high cost of binders and the difficulties of mold pressing and mold releasing which makes continuous and mass production nearly impossible.
BRIEF DESCRIPTION OF INVENTION
The object of the invention is to provide a low cost, continuous processing and steady method for manufacturing packaging materials and sheets using straws as raw material, particularly for manufacturing disposable food containers and seedling-breeding containers.
DETAILS OF THE INVENTION
The present invention provides a method including:
1. cutting straws into segments, drying until moisture content is less than 2% by weight, and pulverizing into powder with 20-50 mesh;
2. stirring the powder of straw, a binder, a lubricant and water in weight parts of 70-88, 0.3-1.0, 0.05-1 and 10-20 respectively, at ambient temperature for 5-15 minutes under 50-80 rpm to obtain a mixture;
3. thermal molding the mixture at a temperature of 100-180° C., and under a pressure of 20-250 Mpa;
The method can further comprise coating the surfaces of the molded product with a water-repellent agent in an amount of 1-7 weight part in the case of waterproofing being necessary.
Alternatively, 0.2 to 0.3 weight part of water-repellent agent can be directly incorporated into the aforementioned mixture.
In the aforementioned process, said straw can be any non-toxic plant straw, such as wheat straw, rice straw, or corn straw. The straw can be firstly cut into 1-2 cm segments, and then dried and pulverized.
In the aforementioned process, said binder can be selected from one of food binders or a combination of two or more food binders so as to be effective cooperatively. Or, polyvinyl alcohol, a mixture of poly (vinyl alcohol) and starch or modified starch can be used. Also, phenolic resin, urea-formaldehyde resin, melamine resin, polyvinyl acetate resin or sodium silicate can be used when manufacturing packaging containers or sheets.
Said lubricant used in the aforementioned process can be one or more selected from the group consisting of polyethylene wax, steratic acid and stearate, such as magnesium stearate, calcium stearate, zinc stearate and aluminum stearate; or soybean oil can be used as a lubricant.
Said water-repellant agent can be ethyl cellulose together with non-toxic solvent, such as ethyl alcohol; or non-toxic silicon water-repellent agent, such as organosilicon resin, or a combination of food binder (such as sodium carboxymethyl cellulose, sodium alginate, etc.), CaCl
2
and white alum in an amount of 1.5-2%, 3-5% and 1-2% respectively; or an aqueous solution of 2-4%, preferably 3%, poly(vinyl alcohol) and 0.5-1%, preferably 1%, melamine.
Other additives, such as reinforcing agent, can also be incorporated into the mixture to improve the intensity of the final product. Reinforcing agent can be one or more selected from the group consisting of sulfates, such as aluminum sulfate, ferric sulfate, zinc sulfate, anhydrous manganese sulfate and chromium sulfate. In the aforementioned method, the thermal molding can be operated under the pressure of 20-25 MPa when manufacturing food containers or seedling breeding container, or under the pressure of 200-250 MPa when manufacturing sheets, which mainly depends on the thickness of the final products.
The method may include further steps such as shaping so as to provide a package container, such as disposable food containers, seedling-breeding containers, or sheets.
The method can also comprise further steps such as decoloring the final product or printing the final product with presetting graphics.
The method according to the present invention can be operated continuously with high productivity. The final product can be degraded within several days which is non-toxic and can even be used as fertilizer or feeding stuff.
REFERENCES:
patent: 3995003 (1976-11-01), Potter et al.
Mills Law Firm PLLC
Theisen Mary Lynn
LandOfFree
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