Multilayer biodegradable mulch and methods for preparing and using the same

• US 6,401,390 B1
• Filed: 08/04/2000
• Issued: 06/11/2002
• Est. Priority Date: 02/02/1998
• Status: Expired due to Term

• Current Assignee: Cascades Canada ULC (Cascades Incorporated)
• Original Assignee: Cascades Multi-Pro Inc. (Cascades Incorporated)
• Inventors: Dubuc, Marc, Labbé, Michel
• Primary Examiner(s): Jordan, Charles T.
• Assistant Examiner(s): Nelson, Judith A.
• Application Number:
  US09/633,102
• Time in Patent Office: 676 Days
• Field of Search: 47/9, 47/485
• US Class Current: 49/9
• CPC Class Codes: B32B 29/06 specially treated, e.g. surfaced, parchmentised
• CPC Class Codes: C09D 167/04 Polyesters derived from hydroxycarboxylic acids, e.g. lactones C09D167/06 takes precedence
• CPC Class Codes: D21H 11/14 Secondary fibres working-up waste paper D21C5/02
• CPC Class Codes: D21H 19/28 Polyesters
• CPC Class Codes: D21H 23/46 Pouring or allowing the fluid to flow in a continuous stream on to the surface, the entire stream being carried away by the paper D21H23/66 takes precedence

Abstract

This invention relates to a mulch having a preprogrammed biodegradability comprising at least two different layers of biodegradable polymer coated onto a sheet of a cellulosic material, one of these layers being a layer of polylactide. The mulch is particularly useful to control weeds in agriculture, horticulture, and forestry industries. The biodegradability of the mulch can further be preprogrammed according to the type of soil, the climatological zone, and the specific applications wherefore it is intended to be used. The present invention is also directed to methods for preparing and using the multilayer coated mulch.

Claims

1. A mulch with a preprogrammed biodegradability comprising:

a sheet of a cellulosic material having an upper face and a lower face; and

at least two different layers of biodegradable polymers coated onto at least one face of said sheet;

wherein one of said at least two different layers is a layer of polylactide.

2. The mulch of claim 1, wherein an uppermost layer among said layers of polymers is a layer of polylactide.

3. The mulch of claim 2, wherein the layer of polylactide and the other(s) of said at least two layers are deposited simultaneously onto said sheet using a co-extrusion process.

4. The mulch of claim 2, wherein said different layers of polymers comprise from about 30 to about 70 w/w percent of polylactide.

5. The mulch of claim 2, wherein said mulch exhibits an increased tearing strength and an increased stiffness when compared to a mulch coated solely with a layer of polylactide.

6. The mulch of claim 2, wherein said mulch is capable of installation on the ground with a mechanical unrolling device.

7. The mulch of claim 2, wherein said mulch does not exhibit a high gloss.

8. The mulch of claim 2, wherein said mulch preprogrammed biodegradability is controlled by varying:

a) the weight of said sheet;

b) the thickness of said sheet; and

/or

c) the weight of the layers of biodegradable polymers coating said sheet.

9. The mulch of claim 8, wherein said biodegradability is preprogrammed according to the type of soil and the climatological zone wherefore said mulch is intended to be used.

10. The mulch of claim 8, wherein said mulch is preprogrammed for an agricultural use and wherein the sheet has a weight between about 40 to about 100 g/m², a thickness between 60 to 175 μ

m and the layers of polymers weigh from about 10 g/m² to about 50 g/m².

11. The mulch of claim 8, wherein said mulch is preprogrammed for a forestry use and wherein the sheet has a weight between about 600 to about 1000 g/m² and a thickness between 600 to 1600 μ

m and the layers of polymers weigh from about 25 g/m² to about 75 g/m².

12. The mulch of claim 2, wherein polylactide is selected from the group consisting of D-polylactide, L-polylactide and mixtures thereof.

13. The mulch of claim 2, wherein the biodegradable polymer(s) other than polylactide is(are) selected from the group consisting of polycaprolactone, poly(tetramethylene adipate-co-terephthalate and mixtures thereof.

14. The mulch of claim 13, wherein the polyester is poly(tetramethylene adipate-co-terephthalate).

15. The mulch of claim 2, wherein the cellulosic material is selected from the group consisting of virgin wood fibers, recycled wood fibers, cotton fibers and mixtures thereof.

16. The mulch of claim 2, wherein the upper face and the lower face of said sheet are both coated with at least two different layers of biodegradable polymers.

17. The mulch of claim 1, further comprising an additional sheet of a cellulosic material having an inside face bounded to at least one of said layers, the mulch thereby forming a sandwich-like structure.

18. An agricultural mulch with a preprogrammed biodegradability comprising:

a sheet of a cellulosic material selected from the group consisting of virgin wood fibers, recycled wood fibers, cotton fibers, and mixtures thereof, the sheet having a weight between about 40 to about 100 g/m² and a thickness between 60 to 175 μ

m; and

at least two different layers of biodegradable polymers coated onto at least one face of said sheet and weighing from about 10 g/m² to about 50 g/m², an uppermost layer among said at least two different layers being a layer of polylactide constituting about 30 to about 70 w/w percent of said layers weight, the other layer(s) being selected from the group consisting of polycaprolactone, poly(tetramethylene adipate-co-terephthalate and mixtures thereof.

19. A method of preparing a biodegradable mulch which comprises:

providing a sheet of a cellulosic material having an upper face and a lower face; and

depositing on at least one face of said sheet by a co-extrusion process at least two different layers of biodegradable polymers, wherein one of said at least two different layers is a layer of polylactide.

20. The method of claim 19, wherein an uppermost layer among said at least two layers is a layer of polylactide.

21. The method of claim 20, wherein said different layers of biodegradable polymers weigh from about 10 g/m² to about 50 g/m² and comprise from about 30 to about 70 w/w percent of polylactide.

22. A method of improving agricultural production comprising:

providing a biodegradable mulch comprising a sheet of a cellulosic material having at least one face coated with two different layers of biodegradable polymers, wherein one of said at least two different layers is a layer of polylactide; and

placing said mulch on the ground to provide a growth zone for plants.

23. The method of claim 22, wherein an uppermost layer among said at least two layers is a layer of polylactide.

24. The method of claim 23, wherein said mulch is deposited on the ground such that said layer of polylactide is in contact with the soil.

25. The method of claim 23, wherein said mulch is deposited on the ground such that said layer of polylactide faces air.

26. The method of claim 22, wherein said mulch is provided in the form of a roll and wherein the mulch is placed on the ground with a mechanical unrolling device.

27. The method of claim 22, wherein said growth zone is thereby free of weeds and has thereby a buffered soil temperature.