DESC:
TECHNICAL FIELD OF THE INVENTION

The invention generally relates to packaging materials, more particularly bio-compostable coating composition with improved performance applied to different packaging materials such as paper, paperboard, cellulose based films like cellophane or other cellulosic combinations, bio-polymeric films such as polylactic acid (PLA), polybutylene adipate terephthalate (PBAT), polybutyl succinate (PBS), polyhydroxy alkanoates (PHA) or combination thereof, films made of milk & animal protein, films made of seaweed and aluminum foil or combinations thereof.

BACKGROUND OF THE INVENTION

Materials such as paper, paperboard, plastic, polystyrene, and even metals are presently used in enormous quantity in the manufacture of articles such as containers, separators, dividers, lids, tops, cans, and other packaging materials. Modern processing and packaging technology allows a wide range of liquid and solid goods to be stored, packaged, and shipped in packaging materials while being protected from harmful elements, such as gases, moisture, light, microorganisms, vermin, physical shock, crushing forces, vibration, leaking, or spilling. Many of these materials are characterized as being disposable, but actually have little, if any, functional biodegradability. For many of these products, the time for degradation in the environment can span decades or even centuries.

Each year, over 100 billion aluminum cans, billions of glass bottles, and thousands of tons of paper and plastic are used in storing and dispensing soft drinks, juices, processed foods, grains, beer and other products. In the United States alone, approximately 5.5 million tons of paper are consumed each year in packaging materials, which represents only about 15% of the total annual domestic paper production.

Packaging materials (e.g., paper, paperboard, plastic, polystyrene, glass, or metal) are all, to varying extents, damaging to the environment. For example, the manufacture of polystyrene products involves the use of a variety of hazardous chemicals and starting materials, such as benzene (a known mutagen and a probable carcinogen). Chlorofluorocarbons (or “CFCs”) have also been used in the manufacture of “blown” or “expanded” polystyrene products. CFCs have been linked to the destruction of the ozone layer.

Due to widespread environmental concerns, there has been significant pressure on companies to discontinue the use of polystyrene products in favour of more environmentally safe materials. Some groups have favoured the use of products such as paper or other products made from wood pulp. However, there remain drawbacks to the sole use of paper due to the tremendous amount of energy that is required to produce it. A strong need to find new, easily degradable materials that meet necessary performance standards remains.

US 7297394B2 discloses biodegradable polymer blends suitable for laminate coatings, wraps and other packaging materials manufactured from at least one “hard” biopolymer and at least one “soft” biopolymer. “Hard” biopolymers tend to be more brittle and rigid and typically have a glass transition temperature greater than about 10° C. “Soft” biopolymers tend to be more flexible and pliable and typically have a glass transition temperature less than about 0° C. While hard and soft polymers each possess certain intrinsic benefits, certain blends of hard and soft polymers have been discovered which possess synergistic properties superior to those of either hard or soft polymers by themselves. Biodegradable polymers include polyesters, polyesteramides, polyesterurethanes, thermoplastic starch, and other natural polymers. The polymer blends may optionally include an inorganic filler. Films and sheets made from the polymer blends may be textured so as to increase the bulk hand feel. Wraps will typically be manufactured to have good “dead-fold” properties so as to remain in a wrapped position and not spring back to an “unwrapped” form.

JPH09235456A relates to providing a biodegradable film which solves the problem of blocking. A biodegradable film containing two or more of a lactic acid-based polymer, a glycol / aliphatic dicarboxylic acid copolymer, and polycaprolactone, an inorganic filler, and an ethylene / vinyl acetate copolymer. If necessary, one or more of a heat stabilizer, a plasticizer, a lubricant and a modified silicone may be contained.

CA 2336898C discloses a compostable biodegradable coating of paper or paperboard consists of an outer layer containing polylactide the weight of which is at the most about 20 g/m2, and of an adhesive layer that binds the outer layer to the paper or paperboard and is of biodegradable polymer material that is coextruded with the polylactide. Suitable materials for the adhesive layer are biodegradable polyesters. The production is by coextrusion of the polylactide layer (6) and the adhesive layer (7) on either one side of the paper or paperboard or on both sides thereof. Products obtained include in particular packages for food stuffs and disposable dishes such as containers for frozen foods, disposable drinking cups, heat-sealed carton packages and packaging wraps.

However, in the existing coated paper and paper boards, the coating material is adsorbed onto the surface and have limited functionality, such as, high gsm (>10), smoothness, printability, and opacity. Apart from that, the methods of prior art based on extrusion are more expensive and the coating is about 20 gsm thick.

Therefore, there remains a need for a biocompostable coating solution which upon application has a low thickness and penetrates into the paper network, and thereby, providing stronger binding, low gsm requirement and improved performance on sealability, water resistance, oil and grease resistance, and strength. In addition, anti-microbial and higher gloss coatings can be incorporated into the paper & paperboards.

OBJECT OF THE INVENTION

The object of present invention is to overcome the above mentioned problems.

The primary object of present invention is to provide a biocompostable coating composition that is non-plastic and biocompostable and penetrates into the paper network, thereby, providing stronger binding, low gsm requirement and improved performance on sealability, water resistance, oil and grease resistance, and strength.

Another object of the present invention is to provide a biocompostable coating composition that on application has a thickness of less than 10 gsm, preferably between 2 to 8 gsm.

A further object of the present invention is to provide a bio compostable coating composition wherein the fibre network participates in the coated substrate binding.

Yet a further objection is to provide an anti-microbial and higher gloss coatings can be incorporated into the paper & paperboards.

Yet another object is to provide a simple and cost effective process of preparation of the biocompostable coating composition.

SUMMARY

According to first aspect of present invention, the invention provides a biocompostable coating composition comprising:
a. at least one biopolymer;
b. at least one media/solvent; and
c. optionally at least one emulsifying agent;
wherein the ratio of the at least one biopolymer and at least one media/solvent is maintained from 1:075. to 1:15.

According to another aspect of present invention, a method of coating a substrate with the biocompostable coating composition comprising steps of:
- providing a substrate; and
- applying the biocompostable coating composition on said substrate on top surface of the substrate or in between layers of substrate by employing any one of gravure, flexo, semiflexo, curtain coating, rod & bar coater, meter coater and like coating technologies or combinations of technologies through a layer by layer coating or in single layer coating method of coating compositions.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the present disclosure. Accordingly, it should be apparent to those skilled in the art that the following description of various embodiments of the present disclosure is provided for illustration purpose only and not for the purpose of limiting the present disclosure as defined by the appended claims and their equivalents.

All terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which various embodiments belong. Further, the meaning of terms or words used in the specification and the claims should not be limited to the literal or commonly employed sense but should be construed in accordance with the spirit of the disclosure to most properly describe the present disclosure.

The terminology used herein is for the purpose of describing particular various embodiments only and is not intended to be limiting of various embodiments. As used herein, the singular forms "a," "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising" used herein specify the presence of stated features, integers, steps, operations, members, components, and/or groups thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, members, components, and/or groups thereof. Also, Expressions such as "at least one of," when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list.

Present invention relates to a biocompostable coating composition, which is efficient and cost effective.

The biocompostable coating composition comprises:
a. at least one biopolymer;
b. at least one media/solvent; and
c. optionally at least one emulsifying agent;
wherein the ratio of the at least one biopolymer and at least one media/solvent is maintained from 1:0.75 to 1:15.

In a preferred embodiment, the range of the ratio lies in between 1:1 to 1:10

The biopolymer can be selected from group comprising but not limited to polylactic acid (B.P.1), polybutyl succinate (B.P.2), polybutylene adipate terephthalate (B.P.3), polyhydroxy alkanoates (B.P.4) and combinations thereof.

The amount of the biopolymer in the composition is about 5 wt % to 57 wt % of the total composition, preferably 10 wt% to 50 wt% of the total composition.

In a preferred embodiment, the biopolymer is selected from B.P.1, B.P.2 and B.P.3 or combination thereof.

The media/solvent can be selected from polar solvents such as but not limited to chlorinated, ketonated, esterified solvents, water.

In a preferred embodiment, the solvent is selected from N-propyl acetate (NPAC), Tetrahydrofuran (THF), Dimethyl formaldehyde (DMF), Dichloromethane (DCM), Dimethylsulfonate (DMSO), Methyl ethyl ketone (MEK), Methylisobutylketone (MIBK), Chloroform, Ethylacetae, Dicholoroethane (DCE) or combination thereof.

To the limited level extent anti-microbial effect will be present in the all polymeric materials but will not be sufficient enough to protect the content/goods/surface, Accordignly, the biocompostable coating composition may further comprise anti-microbial agents so that capacity of microbe killing is enhanced of the biopolymer to protect the content/goods/surface. The anti-microbial agents are preferably micro/nano silver ions particles.

The biocompostable coating composition of the present invention can be used on to any cellulose substrate which has less than 10 gsm thickness in dimension.

The composition coated over or intermittently or binding between the layers of substrates like paper, paper board, cellophane, PLA films, PBAT films, Aluminum foil or combinations thereof through the various coating technologies like gravure, flexo, semiflexo, curtain coating, rod & bar coater, meter coater either independently or combinations of technologies through a layer by layer coating of different coating compositions.

Generally known biocompostable coating have a thickness of at least 20 gsm thickness, which would require a much greater amount of biopolymer to be deposited and therefore add to the cost.

Surprisingly, the biocompostable coating composition of the present invention provides a thickness of less than 10 gsm yet has properties as good as the properties of a 20 gsm or 30 gsm coating.

It is well known that surface coatings form a layer on surface and are usually not known to penetrate into the surface. Surprisingly, the present inventors found that that the coating composition penetrates deeper into the surface, preferably paper, paperboards or cardboards. Such higher penetration indicates stronger binding and improved barrier properties. Consequently, coating requirement (gsm/m2), thus, is significantly reduced.

The advantages of the present biocompostable composition includes high penetrability into the paper network, and thereby, providing stronger binding, low gsm requirement and improved performance on sealability, water resistance, oil and grease resistance, and strength. The fibre network participates in the coated substrate binding. In addition, the biocompostable composition provides anti-microbial and higher gloss finish. Other advantages include the non-plastic and biocompostable nature of such compositions.

The biocompostable coating composition of the present invention can be employed to prepare a two side coated paper and paperboard. The biocompostable coating composition being non-plastic and biocompostable and provide high barrier properties to various types of paper and paper board substrates. It is an alternative to PE Extrusion, PLA extrusion, among others, and it has applications in paperboards, soap carton, cup stock application, paper based packaging. It is also cheaper than the other available alternatives and will find application infor primary, secondary, and tertiary packaging.

Some of the non-limiting working examples are provided below:
S.No Ingredients Wt%
Concentration range
1 B.P.1 5-50%
2 B.P.2
3 B.P.3
4 B.P.4
5 Water 45-95%
6 Chlorinated solvent – media
7 Ketonated solvent – media
8 esterified solvents – media
9 Emulsifying agent (SLS and SLES) – Optional 5-20%

The process of preparation of biocompostable coating solution includes dissolving the at least one biopolymer into the at least one media/solvent at room temperature for about 1 – 3 hours to obtain biocompostable coating solution

Working example A:
S. No. Ingredients Wt%
1 Poly Lactic acid 10%
2. Chlorinated solvent (Dichloromethane) 60%
3 Water 20%
4 Sodium Lauryl Ether Sulphate 10%

OGR – Oil & Grease resistance for this above example A is more than 13 (dependent on GSM – for example 2GSM will be around 12, 3 GSM will be 14 and 6 GSM is 16 depending on the nature of the substrate.). The coating allows heat sealability.

Non-Working Example B:

S.No Ingredients Wt%
Concentration range
1 B.P.1 >60%
2 B.P.3
3 B.P.2
5 Water <40%
6 Chlorinated solvent – media
7 Ketonated solvent – media
8 esterified solvents – media

S.No. Ingredients Wt%
1 B.P.1 60%
2. Chlorinated solvent (Dichloromethane) 30%
3 Water 10%
4 Sodium Lauryl Ether Sulphate -NA-

However, the above formulation is not stable and hence unable to use for coating application over the substrates.
,CLAIMS:1. A biocompostable coating composition comprising:
a. at least one biopolymer;
b. at least one media/solvent; and
c. optionally at least one emulsifying agent;
wherein the ratio of the at least one biopolymer and at least one media/solvent is maintained from 1:0.75 to 1:15.

2. The composition as claimed in claim 1, wherein the ratio of the biopolymer and media/solvent is 1:1 to 1:10.

3. The composition as claimed in claim 1, wherein the amount of biopolymer in the composition is from 5 wt % to 57 wt % of the total composition,

4. The composition as claimed in claim 3, wherein the amount of biopolymer in the composition is from 10 wt% to 50 wt% of the total composition.

5. The composition as claimed in claim 1, wherein said biopolymer is selected from group comprising but not limited to polylactic acid, polybutyl succinate, polybutylene adipate terephthalate, polyhydroxy alkanoates or combinations thereof.

6. The composition as claimed in claim 5, wherein the biopolymer is selected from polylactic acid, polybutylene adipate terephthalate, polybutyl succinate or combinations thereof

7. The composition as claimed in claim 1, wherein media/ solvent is selected from polar solvents.

8. The composition as claimed in claim 6, wherein the polar solvent is selected from chlorinated, ketonated, esterified solvents, and water.

9. The composition as claimed in claim 7 or 8, wherein the polar solvent is selected from N-propyl acetate (NPAC), Tetrahydrofuran (THF), Dimethyl formaldehyde (DMF), Dichloromethane (DCM), Dimethylsulfonate (DMSO), Methyl ethyl ketone (MEK), Methyl iso butyl ketone (MIBK), Chloroform, Ethylacetae, Dicholoroethane (DCE) or combination thereof

10. The composition as claimed in claim 1, wherein said emulsifying agent is selected from sodium lauryl ether sulphate or sodium lauryl sulphate.

11. The composition as claimed in claim 1, comprises anti-microbial agents capable of killing microbes.

12. The composition as claimed in claim 10, wherein the anti-microbial agents are preferably micro/nano silver ions particles.

13. A method of coating a substrate with the biocompostable coating composition as claimed in claims 1-12, comprising steps of:
- providing a substrate; and
- applying the biocompostable coating composition on top surface of the substrate or in between layers of substrate by employing any one of gravure, flexo, semiflexo, curtain coating, rod & bar coater, meter coater and like coating technologies or combinations of technologies through a layer by layer coating or in single layer coating method of coating compositions.

14. The method of coating of a substrate as claimed in claim 13, wherein the substrates are selected from Paper, paper Board, Cellulose based films like cellophane or other cellulosic combinations, Bio-polymeric films such as PLA, PBAT, PBS, PHA or combination thereof, films made of milk & animal protein, films made of seaweed and Aluminum foil or combinations thereof.