Biodegradable polymeric substrate and a method of producing the substrate

Abstract

The present invention discloses a method of making a non-biodegradable flexible packaging substrate biodegradable. The method comprises the steps of (i) providing a substrate web from an unwind to a coating station (402), (ii) applying thin layer of uniform deposition of a curable coating on at least one surface of the substrate partially or completely by the coating station wherein the external surface of the substrate is essentially coated, (iii) curing the coating applied on the substrate web by a curing unit, and (iv) collecting the coated substrate web in roll at rewind. Further, the thickness of the thin layer of uniform deposition is in the range of 0.01 gsm to 10 gsm.

Claims

1. A method of making a non-biodegradable flexible packaging substrate web biodegradable, the method comprising: (a) providing the substrate web from an unwind to a coating station, wherein the substrate web comprises multiple polymeric layers; (b) applying a thin layer of uniform deposition of an enzyme based coating on only an outermost exterior surface of the substrate web partially or completely by the coating station; (c) curing the enzyme based coating applied on the substrate web by a curing unit, wherein the curing unit is one of: (i) a hot air blower; or (ii) an electron beam radiation source; or (iii) a UV lamp/LED radiation source; and (d) collecting the coated substrate web in roll at rewind, wherein: the thin layer of uniform deposition of the enzyme based coating is from 0.01 gsm to 10 gsm; and the enzyme based coating is configured to attract microorganisms to the outermost exterior surface of the substrate web, whereby the microorganisms colonize on the outermost exterior surface of the substrate web and secrete acids and/or enzymes that break down polymer chains of the substrate web to cause biodegradation of the substrate web.

2. The method of claim 1, wherein the substrate web is a laminate comprising the multiple polymeric layers, and wherein the laminates comprises at least one of polyethylene, polypropylene, polyethylene terephthalate, nylon, polystyrene, polyurethane, polyvinyl chloride, and polycarbonate.

3. The method of claim 1, wherein the enzyme based coating is a coating formulation having: natural peptides obtained from edible biological sources; or enzymes obtained from edible biological sources; or proteins obtained from edible biological sources.

4. The method of claim 3, wherein the coating formulation is water or solvent based.

5. The method of claim 3, wherein one or more markers is used with the coating formulation to detect the presence of the enzyme based coating on the outermost exterior surface of the substrate web.

6. The method of claim 5, wherein the marker is a biomarker.

7. The method of claim 5, wherein the marker is a covert marker.

8. The method of claim 1, wherein the coating station is based on rotogravure, flexography or spray, inkjet, dipping, or screen printing process.

9. The method of claim 1, wherein the curing unit is the hot air blower.

10. The method of claim 1, wherein degradation of the biodegradable flexible packaging substrate begins under aerobic or anaerobic environmental condition.

11. The method of claim 1, wherein the curing unit is either the electron beam radiation source or the UV lamp/LED radiation source.

12. The method of claim 11, wherein the curing unit is the electron beam radiation source.

13. The method of claim 11, wherein the curing unit is the UV lamp/LED radiation source.

14. The method of claim 1, wherein the enzyme based coating is applied on the outermost exterior surface of the substrate web inline during manufacturing of the substrate web in a roll-to-roll process.

15. A biodegradable flexible packaging substrate web obtained by the method according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) These and other advantages and features of the present invention, as well as methods of operation and economies of manufacture, will become apparent to one skilled in the art to which the present invention pertains based upon the following detailed description and the appended drawings, all of which form a part of this application. In the drawings:

(2) FIG. 1 shows the presence of enzyme based additive dispersed in the entire thickness of the substrate as known in the art;

(3) FIG. 2 is flow-chart depicting a method to apply a thin layer of uniform deposition of an enzyme based coating on at least one surface of a flexible substrate to make biodegradable flexible substrate, in accordance with an embodiment of the present invention; and

(4) FIG. 3A-3C depicts different stages of biodegradation of the biodegradable polymeric flexible substrate made by applying enzyme based coating on one surface of the flexible substrate, in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

(5) While the present invention has been described in connection with what are currently considered to be the most practical and preferred embodiments, it is to be understood that various arrangements and alternative embodiments are intended to be included within the scope of the appended claims.

(6) As shown in FIG. 1, the additives (10) are dispersed in the entire thickness of the substrate (11) and very less quantity of the additives is available on the surface of the substrate as discussed earlier in the background section.

(7) The present invention provides a method for coating that converts non-biodegradable polymeric substrates into biodegradable at fraction of cost.

(8) The present invention relates to a method of applying a thin uniform layer (101) of enzyme based coating/additives on at least one surface of the polymer substrate to induce biodegradability. The present invention requires quite less amount of enzyme based formulation compared to the prior art and thus make the process cost effective. The present invention requires up to 90% less amount of enzyme based coating formulations compared to the quantity used in the prior art. The coating is applied in roll-to-roll process.

(9) FIG. 2 is flow-chart depicting a method (200) to apply a thin uniform layer of an enzyme based coating on at least one surface of a flexible substrate to make the substrate biodegradable, in accordance to an embodiment of the present invention. The method (200) comprising providing a substrate web from an unwind to a coating station at step (202); applying a thin uniform layer of a curable coating by the coating station at step (204); curing the coating applied on the surface of substrate web by a curing unit at step (206); and collecting the coated substrate web in roll at rewind (208), wherein thickness of the layer of coating is in the range of 0.01 gsm to 10 gsm.

(10) The non-biodegradable polymeric substrate web is introduced to the process as a supply roll on unwind for continuous feed to the coating process. The unwind holds the roll of the substrate to be coated and provides the substrate web to the coating station in line. The substrate web onto which the coating to be applied is passed through the coating station. The coating station(s) apply the enzyme based coating on one or both surfaces of the substrate web. Thereafter the coated substrate is passed through a curing unit in order to cure the coating applied before collecting the coated substrate in roll at rewind.

(11) The coating may also be applied on the surface(s) of the substrate in-line during the production of substrate web at any suitable location, before collecting on the rewind. After coating of the surface(s), the coated substrate web is passed through curing unit to cure the coating.

(12) It should be appreciated that one or both (interior and exterior) surfaces of the packaging substrate may be coated based on the requirement and/or food or product to packaged. In case of contamination sensitive product or food to be packaged, only exterior surface of the substrate is coated with the enzyme based coating having desired biodegradation effect.

(13) To check the presence of enzyme based biodegradable coating on the substrate surface, unique biomarkers may be used in coating formulations, which can be detected using suitable means after application.

(14) The flexible substrate may be single layer or multilayer films or laminates of at least one of the group of, but not limited to, PE, PP, PET, Nylon,

(15) Polystyrene including foamed, PU, PVC, PC etc. The coating may be applied by various methods known in the art. The coating stations may be based on rotogravure, flexography, spraying, inkjet, dipping, screen printing etc. The coating may be provided inline during the manufacturing of the substrate or offline after the substrate is formed.

(16) In case of laminate there are multiple polymeric layers which may be a single layer film or multilayer films. At least one surface of at least one polymeric layer may be coated with enzyme based coating and then laminated together to form a laminate. Essentially the outer most exterior surface of the laminate is coated with the enzyme based coating to attract the bacteria to initiate the process. However, only at least the outside surface of the finished laminate may also be coated with the enzyme coating.

(17) The coating is cured by curing unit that may be a hot air blower and/or radiation source such as but not limited to Electron Beam or UV lamp/LED.

(18) The formulation of the enzyme based coating may include, but not limited to, natural peptides/enzymes/proteins obtained from edible biological sources such as plant or vegetables etc. The coating formulation may be solvent or water based.

(19) FIG. 3A-3C depict stages of biodegradation of the biodegradable polymeric flexible substrate, made by applying enzyme based coating (101) on one surface of the flexible substrate, under aerobic or anaerobic environmental condition in soil, in accordance with an exemplary embodiment of the present invention.

(20) As shown in FIG. 3A when a product, such as packaging, made from the coated substrate is disposed of after the use, it comes in contact with soil. The microorganisms (102) such as bacteria, fungi etc. present in soil gets attracted towards the coated substrate due to the enzyme present in coating (101) on the surface of the substrate. The disposal of packaging or the substrate (100) in any other form in soil, where suitable microbes are found in abundance, initiate and propagate the process of biodegradation of polymeric surface. The microbes may be aerobic or anaerobic. Once the microbes are accumulated on the surface of the substrate, they start colony formation on the surface of the substrate. As depicted not all type of microbes succeed in colony formation, rather only specific type of microorganisms which can utilize the substrate as their food deposit on the substrate.

(21) After colonisation, the microbes start fragmenting the substrate surface resulting in biodegradation of the coated substrate and the coated substrate starts depleting layer by layer thereby reducing the thickness of the substrate as depicted in FIGS. 3B & 3C.

(22) Under aerobic conditions when oxygen is readily available, such as when the packaging remains on the soil open to atmosphere, aerobic heterotrophic micro-organisms are mainly responsible for the degradation of such polymers, with microbial biomass, CO.sub.2, and H.sub.2O as the by-products. Under anaerobic conditions, when the packaging remains in landfills or enclosed spaces where oxygen is not available or is very low in concentration, anaerobic microorganisms are responsible for polymer degradation and the by products are microbial biomass, CO.sub.2, CH.sub.4 and H.sub.2O under methanogenic conditions.

(23) The Speed of bio degradation is generally affected by type of polymer, environmental microbial conditions, the concentration of peptide/enzyme/protein in the enzyme based coating and the thickness of the substrate.

(24) While the present invention has been described in connection with what are currently considered to be the most practical and preferred embodiments, it is to be understood that various arrangements and alternative embodiments are intended to be included within the scope of the appended claims.