BIODEGRADABLE AGRICULTURAL FILM
First Claim
1. A degradable plastic mulching film comprising:
- two longitudinal bands each adjacent to a respective longitudinal edge of the film, the bands comprising a first degradant;
a middle section between the two bands, the middle section comprising a second degradant;
the film being adapted for use with the bands buried in soil and the middle section exposed to ambient light, the first and second degradants and their respective weight percentages being selected such that, in use, both the buried bands and the exposed middle section degrade sufficiently by the time of a further cycle of cultivation that they do not interfere with the operation of agricultural equipment.
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Accused Products
Abstract
A degradable plastic film for use as an agricultural mulch film comprises two longitudinal bands each adjacent to a respective longitudinal edge of the film, and a middle section between the bands. The bands and middle section contain degradants. In use, the bands along the edges of the mulch film are buried in the soil and the middle section is exposed to sunlight. By reason of different degradants in the bands and middle section respectively, or different levels of the same degradants, the entire film degrades by the time of the next cycle of cultivation. The film is produced by means of extrusion from two extruders through one circular die which has a die opening with one segment which receives resin with one degradant and another segment which receives resin with a second degradant. The extruded cylindrical film is blown and then slit longitudinally.
48 Citations
39 Claims
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1. A degradable plastic mulching film comprising:
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two longitudinal bands each adjacent to a respective longitudinal edge of the film, the bands comprising a first degradant; a middle section between the two bands, the middle section comprising a second degradant; the film being adapted for use with the bands buried in soil and the middle section exposed to ambient light, the first and second degradants and their respective weight percentages being selected such that, in use, both the buried bands and the exposed middle section degrade sufficiently by the time of a further cycle of cultivation that they do not interfere with the operation of agricultural equipment. - View Dependent Claims (2, 3, 4, 5, 6, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 32, 33, 39)
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7. A degradable plastic film comprising:
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two longitudinal bands each adjacent to a respective longitudinal edge of the film, the bands comprising a first degradant; a middle section between the two bands, the middle section comprising a second degradant; the first degradant having a higher level of thermal-activation than the second degradant. - View Dependent Claims (8)
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9. A degradable plastic film comprising two longitudinal bands each adjacent to a respective longitudinal edge of the film, and a middle section between the two bands, the bands and the middle section containing a degradant, the weight percent of the degradant in the bands being higher than the weight percent of the degradant in the middle section.
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25. A method of making a degradable plastic film which comprises two longitudinal bands each adjacent to a respective longitudinal edge of the film, the bands comprising a first degradant, and a middle section between the two bands, the middle section comprising a second degradant, the method comprising the steps of:
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(a) providing an extrusion die having a circular die opening, the die opening comprising a first segment and a second segment; (b) delivering plastic resin comprising the first degradant from a first extruder to the first segment of the die opening; (c) delivering plastic resin comprising the second degradant from a second extruder to the second segment of the die opening; (d) extruding the plastic resins through the die opening to produce a cylindrical plastic film having a first longitudinally-extending portion comprising the first degradant and a second longitudinally-extending portion comprising the second degradant; (e) blowing the cylindrical film to expand it; and (f) slitting the expanded cylindrical film longitudinally through the first longitudinally-extending portion to make two longitudinal edges, with a part of the first longitudinally-extending portion adjacent to each respective edge. - View Dependent Claims (26, 27, 28, 29, 30, 31, 34, 35, 36, 37)
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38. A method of making a degradable plastic mulching film which comprises two longitudinal bands each adjacent to a respective longitudinal edge of the film, the bands comprising a first degradant, and a middle section between the two bands, the middle section comprising a second degradant, the film being adapted for use with the bands buried in soil and the middle section exposed to ambient light, the first and second degradants and their respective weight percentages being selected such that, in use, both the buried bands and the exposed middle section degrade sufficiently by the time of a further cycle of cultivation that they do not interfere with the operation of agricultural equipment, the method comprising the steps of:
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(a) providing an extrusion die having a circular die opening, the die opening comprising a first segment and a second segment; (b) delivering plastic resin comprising the first degradant from a first extruder to the first segment of the die opening; (c) delivering plastic resin comprising the second degradant from a second extruder to the second segment of the die opening; (d) extruding the plastic resins through the die opening to produce a cylindrical plastic film having a first longitudinally-extending portion comprising the first degradant and a second longitudinally-extending portion comprising the second degradant; (e) blowing the cylindrical film to expand it; and (f) slitting the expanded cylindrical film longitudinally through the first longitudinally-extending portion to make two longitudinal edges, with a part of the first longitudinally-extending portion adjacent to each respective edge.
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Specification