FIELD OF THE INVENTION
The invention relates to coating materials and methods for preparation thereof.
BACKGROUND OF THE INVENTION
Plastic packaging is subjected to pressure from existing and proposed environmental and disposal regulations, and market based sustainability 5 initiatives. It presents a major disposal problem for companies and municipalities as it is lightweight and bulky and so does not lend itself to a viable economic and environmentally responsible recycling operation due to expensive handling and transportation costs. It is not biodegradable, which makes disposal in soil or composting operations untenable. Further, issues such as sustainability, industrial 10 ecology, biodegradability, and recyclability are becoming major considerations in a company's product packaging design, especially with single use disposable packaging. Natural biopolymers provide biodegradable, sustainable solutions for the manufacture of short-life, single use disposable packaging, consumer goods, and marine plastics. Today numerous types of biodegradable plastic films have 15 made their ways into the market. However, the vast majority of the so-called biodegradable plastics the main component of these films is not biodegradable.
Problems associated with the handling of environmental waste, particularly the large amount of discardable plastic products and the limited volume of land fill facilities, has placed added emphasis on developing products which are either 20 biodegradable or recyclable. This is particularly true in the packaging areas where large volumes of discardable plastic packaging materials are used in various forms, including containers, sheets, films, tubing and fillers. Because of this large increase in the use of plastic materials, it has been proposed to make throwaway materials from biodegradable plastics to alleviate the waste disposal problems. 25
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Several reasons have prevented the development and likelihood of developing this technology except in special situations. First of all, the high volume packaging plastics such as polyethylene, polystyrene, polypropylene and polyethylene terephthalate are low cost and are not biodegradable. Attempts to make such materials biodegradable by blending them with biodegradable fillers or additives 5 have not been overly successful. Those existing plastics which are biodegradable, are deficient in properties required in most packaging applications and are more expensive than commonly used packaging plastics. Degradable plastics are more difficult to recycle than nondegradable plastics. Furthermore, another reason the nondegradable plastics are preferred in landfill sites is because they do not 10 generate noxious or toxic gases.
Currently, the plastic waste is either provided to garbage incinerators or accumulates in refuse dumps, with both of the above-mentioned solutions for waste disposal being associated with problems for the environment.
In addition, paper and composite materials are often provided with a coating, such 15 as e.g. polymeric or wax coatings, for increasing the strength of the paper stock or of the basis composite material, imparting water resistance, enhancing gloss, improving barrier properties, etc. These polymeric or wax coatings give however rise to various problems when articles comprising polymeric or wax coatings are subjected to recycling or re-pulping processes. 20
Several Biodegradable polymers are already known in the state of the art and comprise materials e.g. on the basis of poly(glycolic acid), poly(epsilon-caprolactone), poly(lactic acid), and polydioxanone. These polymers require however rather complicated production steps and are rather cost-intensive and
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therefore currently mainly restricted to high value medical applications requiring bioabsorbable materials.
Paper packaging products in general (such as paper cup, paper bowl, paper plate, paper box and paper lunch box, drink box, nonwoven cloth, and paper container, etc), in order for the food contained not to seep out, usually will coat a layer of PE 5 film on the inside of the paper board of the paper product. However, said film often could not degrade naturally and create secondary damage to the environment.
Thus, there is a need in the art to obviate the above problem and to provide coating materials, which do not add to environmental pollution and assist to 10 simplify recycling or repulping processes.
SUMMARY OF THE INVENTION-
An aspect of the present invention relates to a coating material comprising at least one biopolymer, at least one synthetic polymer and at least one 15 antimicrobial agent.
Another aspect of the present invention discloses a method of forming a coating material, the method comprising of mixing at least one biopolymer, at least one synthetic polymer and at least one antimicrobial agent to form a solution and heating the solution to obtain a polymer solution of the coating material. 20
In another aspect of the present invention a method of forming a coating material comprises of mixing at least one biopolymer, at least one synthetic polymer and at least one anti microbial agent to form a solution. A crosslinking agent or curing agent is added in the presence of an initiating agent to the above solution
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to form a mixture. The mixture is heated to obtain a polymer solution of the coating material.
DESCRIPTION OF THE INVENTION
An embodiment of the present invention provides a coating material comprising at least one biopolymer, at least one synthetic polymer and at least one 5 antimicrobial agent.
In an embodiment of the present invention, the biopolymer is selected from natural and/or modified starch. The synthetic polymer is selected from polyvinyl alcohol, copolymers of hydrolyzed or partially hydrolyzed vinyl acetate such as ethylene-vinyl acetate (EVA), vinyl chloride-vinyl acetate, N-vinylpyrrolidone-10 vinyl acetate and maleic anhydride-vinyl acetate or mixtures thereof. The synthetic polymer is preferably polyvinyl alcohol.
In a preferred embodiment of the present invention, the biopolymer is starch and the synthetic polymer is polyvinyl alcohol.
The coating material in the aforesaid embodiments comprises biopolymer in the 15 range of 1.5 wt% - 7.5 wt %, preferably 2 wt%-7 wt%, more preferably 4wt% - 5wt %, the synthetic polymer is present in the range of 1.5 wt% - 7.5 wt %, preferably 2 wt%-7 wt%, more preferably 4wt% - 5wt %.
In another embodiment of the present invention a method of forming a coating material comprises of: 20
mixing at least one biopolymer, at least one synthetic polymer and at least one antimicrobial agent to form a solution; and
heating the solution to obtain a polymer solution of the coating material
The mixture of biolpolymer, synthetic polymer and antimicrobial agent is heated at a temperature of more than 70°C. 25
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In another embodiment of the present invention a method of forming a coating material comprises of:
mixing at least one biopolymer, at least one synthetic polymer and at least one anti microbial agent
adding a crosslinking or curing agent in the presence of an initiating 5 agent to the above solution to form a mixture; and
heating the mixture to obtain a polymer solution of the coating material
The mixture of biopolymer, synthetic polymer, antimicrobial agent along with a crosslinking or curing agent and initiating agent is heated at a temperature of more 10 than 70°C.
In the aforesaid embodiment, the method of forming a coating material further comprises adding a compatibilizer to the polymer solution. The compatibilizer is selected from the group comprising of maleic anhydride, borax, butyl and adipate co terephthalate or a mixture thereof. Preferably the compatibilizer is maleic anhydride. 15
According to one embodiment of the present invention a method of forming a coating on a substrate comprises of applying the coating material as mentioned and prepared in the aforesaid embodiments on a pre-heated substrate. The coating material is applied on the substrate pre-heated at a temperature of more than 70°C.
In one embodiment the coating material is heated at a temperature of more than 20 70°C before applying it on a substrate.
One embodiment of the present invention provides a method of forming a coating on a substrate. The method comprises of -
mixing at least one biopolymer, at least one synthetic polymer and at least one antimicrobial agent to form a solution; 25
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heating the solution to obtain a polymer solution of the coating material; and
applying the polymer solution on the substrate surface to obtain the coating on the surface.
In another embodiment of the present invention a method of forming a coating on a substrate comprises of 5
mixing at least one biopolymer, at least one synthetic polymer and at least one antimicrobial agent to form a solution;
adding a crosslinking or curing agent in the presence of an initiating agent to the above solution to form a mixture; and
heating the solution to obtain a polymer solution of the coating material . 10
In one embodiment of the present invention the coating material is applied on the substrate pre-heated at a temperature of more than 70°C, preferably in the range of 70-80 °C.
In another embodiment of the present invention the coating material is heated at a temperature of more than 70°C before applying it on a substrate, preferably in the 15 range of 70-80 °C.
In an embodiment of the present invention the coating material is applied on a substrate at room temperature.
In the aforesaid embodiment, the method of forming a coating on a substrate further comprises adding a compatibilizer to the polymer solution. The 20 compatibilizer is selected from the group comprising of maleic anhydride, borax, butyl and adipate co terephthalate or a mixture thereof. Preferably the compatibilizer is maleic anhydride.
In the aforesaid embodiments, the curing agent or cross linking agent is selected from citric acid, a mixture of gluteraldehyde with sodium sulfate, sulphuric acid 25
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and HCl, epichlorohydrine, formaldehyde or a mixture thereof . The crosslinking or curing agent is preferably citric acid.
The initiating agent used in the present invention is sodium hypophosphite.
In the aforesaid embodiments, the biopolymer is selected from natural and/or modified starch. 5
The synthetic polymer in the aforesaid embodiments is selected from polyvinyl alcohol, copolymers of hydrolyzed or partially hydrolyzed vinyl acetate such as ethylene-vinyl acetate (EVA), vinyl chloride-vinyl acetate, N-vinylpyrrolidone-vinyl acetate and maleic anhydride-vinyl acetate or mixtures thereof. The synthetic polymer is preferably polyvinyl alcohol. 10
In a preferred embodiment of the present invention, the biopolymer is starch and the synthetic polymer is polyvinyl alcohol.
The starting polyvinyl alcohols preferably have a mean molecular weight of at least 2000 Da. Polyvinyl alcohols that can be derivatized in accordance with the invention preferably have a molecular weight of at least 10,000 Da. As an upper 15 limit, the polyvinyl alcohols may have a molecular weight of up to 1,000,000 Da. Preferably, the polyvinyl alcohols have a molecular weight of up to 300,000 Da, especially up to approximately 100,000 Da and especially preferably up to approximately 30,000 Da.
The polyvinyl alcohols usually have a poly(2-hydroxy)ethylene structure. The 20 polyvinyl alcohols derivatized in accordance with the disclosure may, however, also comprise hydroxy groups in the form of 1,2-glycols.
In the aforesaid embodiments the antimicrobial agent include, without limitation, bis-biguanide salts such as chlorhexidine digluconate, chlorhexidine diacetate, chlorhexidine dihydrochloride, chlorhexidine diphosphanilate), rifampin, 25
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minocycline, silver compounds such as silver chloride, silver oxide, silver sulfadiazine, triclosan, octenidine dihydrochloride, quaternary ammonium compounds such as benzalkonium chloride, tridodecyl methyl ammonium chloride, didecyl dimethyl ammonium chloride, chloroallyl hexaminium chloride, benzethonium chloride, methylbenzethonium chloride, cetyl trimethyl ammonium 5 bromide, cetyl pyridinium chloride, dioctyldimethyl ammonium chloride), iron-sequestering glycoproteins such as lactoferrin, ovotransferrin/conalbumin), cationic polypeptides such as protamine, polylysine, lysozyme, surfactants (e.g., SDS, Tween-80, surfactin, Nonoxynol-9) and zinc pyrithione. Further preferred antimicrobial agents include broad-spectrum antibiotics such as quinolones, 10 fluoroquinolones, aminoglycosides and sulfonamides), and antiseptic agents such as iodine, methenamine, nitrofurantoin, validixic acid. penicillins; tetracyclines; aminoglycosides, such as gentamicin and Tobramycin.TM.; polymyxins; rifampicins; bacitracins; erythromycins; vancomycins; neomycins; chloramphenicols; miconazole; quinolones, such as oxolinic acid, norfloxacin, 15 nalidixic acid, pefloxacin, enoxacin, and ciprofloxacin; sulfonamides; nonoxynol 9; fusidic acid; cephalosporins or mixtures thereof
In another embodiment of the present invention, at least one antimicrobial agent incorporated in the polymeric layer comprises an organic antimicrobial agent, an inorganic antimicrobial agent, or a mixture of two or more of any of the foregoing 20 antimicrobial agents. The antimicrobial agent can be microbicidal and kill microbes, or can be microbistatic and prevent growth or reproduction of microbes. The term "microbes" as used herein refers to microorganisms which include bacteria, fungi, plants, and protozoans.
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In another embodiment, the organic antimicrobial agent comprises a natural antimicrobial agent to include for example phytochemicals such as citric acid, a synthetic antimicrobial agent to include for example triclosan and quaternary ammonium halides, or a mixture of two or more of any of the foregoing organic antimicrobial agents. 5
In one embodiment of the present invention the antimicrobial agent is a plant extract or a combination of different plant extracts.
In a preferred embodiment of the present invention the antimicrobial agent is neem extract.
The source of neem extract is Azadirechta indica and the geographical origin is 10 Asia. The neem extract used in the invention is commercially available.
In another embodiment, the antimicrobial agent may also be selected from a wide range of known antibiotics and antimicrobials. Suitable materials are discussed in "Active Packaging of Food Applications" A. L. Brody, E. R. Strupinsky, and L. R. Kline, Technomic Publishing Company, Inc. Pennsylvania (2001). Additional 15 examples of antimicrobial agents suitable for practice of the invention include benzoic acid, sorbic acid, nisin, thymol, allicin, peroxides, imazalil, triclosan, benomyl, antimicrobial metal-ion exchange material, metal colloids, metal salts, anhydrides, and organic quaternary ammonium salts.
In another embodiment of the present invention an alcohol is added to the solution 20 of biopolymer and synthetic polymer, preferably starch and the polyvinyl alcohol.
In another embodiment of the present invention an alcohol such as ethylene glycol, glycerol, polyethylene glycol or sorbitol, is added to the solution of starch and the polyvinyl alcohol.
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In one embodiment of the present invention the biopolymer, preferably starch and the synthetic polymer, preferably polyvinyl alcohol is in a ratio from 1:4 to 4:1.
In another embodiment the biopolymer, preferably starch and the synthetic polymer, preferably polyvinyl alcohol solution is in a ratio of 1:1.
One embodiment of the present invention provides ‘on the spot’ coating by 5 preparing the homogeneous polymer solution in advance and storing it, and at the time of application, adding the requisite amount of curing agent and then applying the coating solution on the heated substrate surface to achieve the coating/polymer film.
One embodiment of the present invention provides ‘on the spot’ coating by 10 preparing the polymer solution in advance and storing it, and at the time of application, adding the requisite amount of curing agent and then applying the heated pre-coating solution on the heated substrate surface to achieve the coating/polymer film.
The present invention is directed to a biodegradable film that is generally intended 15 for use in the packaging of items, such as food products, medical products, garments, garbage, absorbent articles (e.g., diapers), tissue products, and so forth. The film is formed from a blend that contains starch and polyvinyl alcohol. Starch is a relatively inexpensive natural polymer that is also renewable and biodegradable. Polyvinyl alcohol is likewise an inexpensive synthetic polymer 20 that is biodegradable and renewable, yet also capable of providing increased tensile strength to the film. Although providing a good combination of biodegradability/renewability and increased tensile strength, the polyvinyl alcohol is also relatively rigid and can result in films having a relatively high stiffness (e.g., high modulus of elasticity) and low ductility. 25
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Coating Components
Starch: Starch is a natural polymer composed of amylose and amylopectin. Amylose is essentially a linear polymer having a molecular weight in the range of 100,000-500,000, whereas amylopectin is a highly branched polymer having a molecular weight of up to several million. Any natural (unmodified) and/or 5 modified starch may be employed in the present invention. Modified starches, for instance, are often employed that have been chemically modified by typical processes known in the art (e.g., esterification, etherification, oxidation, acid hydrolysis, enzymatic hydrolysis, etc.). Starch ethers and/or esters may be particularly desirable, such as hydroxyalkyl starches, carboxymethyl starches, etc. 10 The hydroxyalkyl group of hydroxylalkyl starches may contain, for instance, 2 to 10 carbon atoms, in some embodiments from 2 to 6 carbon atoms, and in some embodiments, from 2 to 4 carbon atoms. Representative hydroxyalkyl starches such as hydroxyethyl starch, hydroxypropyl starch, hydroxybutyl starch, and derivatives thereof. Starch esters, for instance, may be prepared using a wide 15 variety of anhydrides (e.g., acetic, propionic, butyric, and so forth), organic acids, acid chlorides, or other esterification reagents. The degree of esterification may vary as desired, such as from 1 to 3 ester groups per glucosidic unit of the starch.
Regardless of whether it is in a native or modified form, the starch may contain different percentages of amylose and amylopectin, different size starch granules 20 and different polymeric weights for amylose and amylopectin. High amylose starches contain greater than about 50% by weight amylose and low amylose starches contain less than about 50% by weight amylose. Although not required, low amylose starches having an amylose content of from about 10% to about 40% by weight, and in some embodiments, from about 15% to about 35% by weight, 25
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are particularly suitable for use in the present invention. Such low amylose starches typically have a number average molecular weight ("M.sub.n") ranging from about 50,000 to about 1,000,000 grams per mole, in some embodiments from about 75,000 to about 800,000 grams per mole, and in some embodiments, from about 100,000 to about 600,000 grams per mole, as well as a weight average 5 molecular weight ("M.sub.w") ranging from about 5,000,000 to about 25,000,000 grams per mole, in some embodiments from about 5,500,000 to about 15,000,000 grams per mole, and in some embodiments, from about 6,000,000 to about 12,000,000 grams per mole. The ratio of the weight average molecular weight to the number average molecular weight ("M.sub.w/M.sub.n"), i.e., the 10 "polydispersity index", is also relatively high. For example, the polydispersity index may range from about 20 to about 100. The weight and number average molecular weights may be determined by methods known to those skilled in the art.
Polyvinyl alcohol: Polyvinyl alcohols which can be used as prepolymer 15 backbones are commercially available PVAs, for example Vinol.RTM. 107 from Air Products (MW=22,000 to 31,000 Da, 98-98.8% hydrolyzed), Polysciences 4397 (MW=25,000 Da, 98.5% hydrolyzed), BF 14 from Chan Chun, Elvanol.RTM. 90-50 from DuPont and UF-120 from Unitika. Other producers are, for example, Nippon Gohsei (Gohsenol.RTM.), Monsanto (Gelvatol.RTM.), 20 Wacker (Polyviol.RTM.) or the Japanese producers Kuraray, Deriki, and Shin-Etsu.
It is also possible to use copolymers of hydrolyzed or partially hydrolyzed vinyl acetate, which are obtainable, for example, as hydrolyzed ethylene-vinyl acetate (EVA), or vinyl chloride-vinyl acetate, N-vinylpyrrolidone-vinyl acetate, and 25
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maleic anhydride-vinyl acetate. If the prepolymer backbones are, for example, copolymers of vinyl acetate and vinylpyrrolidone, it is again possible to use commercially available copolymers, for example the commercial products available under the name Luviskol.RTM. from BASF. Particular examples are Luviskol VA 37 HM, Luviskol VA 37 E and Luviskol VA 28. If the prepolymer 5 backbones are polyvinyl acetates, Mowilith 30 from Hoechst is particularly suitable.
The PVA system can be a fully hydrolyzed PVA, with all repeating groups being --CH.sub.2-CH(OH) or a partially hydrolyzed PVA with varying proportions (25% to 1% ) of pendant ester groups. PVA with pendant ester groups have repeating 10 groups of the structure --CH.sub.2-CH(OR) or in a brief form PVA-(OR) where PVA is --CH.sub.2CH repeating units, R is H, COCH.sub.3 group or longer alkyls, as long as the water solubility of the PVA is preserved. The ester groups can also be substituted by acetaldehyde or butyraldehyde acetals that impart a certain degree of 15 hydrophobicity and strength to the PVA. For an application that requires an oxidatively stable PVA, the commercially available PVA can be broken down by NalO.sub.4-KMnO.sub.4 oxidation to yield a small molecular weight (3-4K) PVA.
Other Components: In addition to the components noted above, other additives 20 may also be incorporated into the film of the present invention, such as melt stabilizers, processing stabilizers, heat stabilizers, light stabilizers, antioxidants, heat aging stabilizers, whitening agents, antiblocking agents, bonding agents, etc. Phosphite stabilizers (e.g., IRGAFOS available from Ciba Specialty Chemicals of Terrytown, N.Y. and DOVERPHOS available from Dover Chemical Corp. of 25
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Dover, Ohio) are exemplary melt stabilizers. In addition, hindered amine stabilizers (e.g., CHIMASSORB available from Ciba Specialty Chemicals) are exemplary heat and light stabilizers. Further, hindered phenols are commonly used as an antioxidant in the production of films. Some suitable hindered phenols include those available from Ciba Specialty Chemicals under the trade name 5 "Irganox.RTM.", such as Irganox.RTM. 1076,1010, or E 201. Moreover, bonding agents may also be added to the film to facilitate bonding of the film to additional materials (e.g., nonwoven web). Examples of such bonding agents include hydrogenated hydrocarbon resins. Other suitable bonding agents are described in U.S. Pat. No. 4,789,699 to Kieffer et al. and U.S. Pat. No. 5,695,868 to 10 McCormack, which are incorporated herein in their entirety by reference thereto for all purposes. When employed, additives (e.g., lubricant, antioxidant, stabilizer, etc.) may each be present in an amount of from about 0.001 wt. % to about 1 wt. %, in some embodiments, from about 0.005 wt. % to about 1 wt. %, and in some embodiments, from 0.01 wt. % to about 0.5 wt. % of the blend used to form the 15 film.
The coating material of the present invention can also contain any combination of additional medicinal compounds. Such medicinal compounds include, but are not limited to, antibiotics, antifungal agents, antiviral agents, antithrombogenic agents, anesthetics, anti-inflammatory agents, analgesics, anticancer agents, 20 vasodilation substances, antibacterial agents, wound healing agents, angiogenic agents, angiostatic agents, immune boosting agents, growth factors, and other biological agents. and combinations of such compounds and similar compounds.
Modifications: The compositions of the present invention are highly versatile. A number of characteristics can be easily modified, making the materials suitable for 25
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a number of applications. For example, the polymer backbones can include co-monomers to add desired properties, such as, for example, thermoresponsiveness, degradability, gelation speed, and hydrophobicity. Modifiers can be attached to the polymer backbone (or to pendant groups) to add desired properties, such as, for example, thermoresponsiveness, degradability, hydrophobicity, and 5 adhesiveness. Active agents can also be attached to the polymer backbone using the free hydroxyl groups, or can be attached to pendant groups.
Coat/Polymer film formation: The film or coating of the present invention may be mono- or multi-layered. Multilayer films may be prepared by co-extrusion of the layers, extrusion coating, or by any conventional layering process. Such 10 multilayer films normally contain at least one base layer and at least one skin layer, but may contain any number of layers desired. For example, the multilayer film may be formed from a base layer and one or more skin layers, wherein the base layer is formed from the blend of the present invention. In most embodiments, the skin layer(s) are also formed from the blend as described above. 15 It should be understood, however, that other polymers may also be employed in the skin layer(s).
Any known technique may be used to form a film from the compounded material, including blowing, casting, flat die extruding, etc. In one particular embodiment, the film may be formed by a blown process in which a gas (e.g., air) is used to 20 expand a bubble of the extruded polymer blend through an annular die. The bubble is then collapsed and collected in flat film form. Processes for producing blown films are described, for instance, in U.S. Pat. No. 3,354,506 to Raley; U.S. Pat. No. 3,650,649 to Schippers; and U.S. Pat. No. 3,801,429 to Schrenk et al., as well as U.S. Patent Application Publication Nos. 2005/0245162 to McCormack, et 25
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al. and 2003/0068951 to Boggs, et al., all of which are incorporated herein in their entirety by reference thereto for all purposes. In yet another embodiment, however, the film is formed using a casting technique.
Once cast, the film may then be optionally oriented in one or more directions to further improve film uniformity and reduce thickness. Orientation may also form 5 micropores due to the presence of the filler, thus providing breathability to the film. For example, the film may be immediately reheated to a temperature below the melting point of one or more polymers in the film, but high enough to enable the composition to be drawn or stretched. In the case of sequential orientation, the "softened" film is drawn by rolls rotating at different speeds of rotation such that 10 the sheet is stretched to the desired draw ratio in the longitudinal direction (machine direction). This "uniaxially" oriented film may then be laminated to a fibrous web. In addition, the uniaxially oriented film may also be oriented in the cross-machine direction to form a "biaxially oriented" film. For example, the film may be clamped at its lateral edges by chain clips and conveyed into a tenter oven. 15 In the tenter oven, the film may be reheated and drawn in the cross-machine direction to the desired draw ratio by chain clips diverged in their forward travel.
The coating material of the present invention comprising of biopolymer, synthetic polymer and antimicrobial agent has excellent mechanical properties such as tear strength, dimensional stability, and tensile strength. It also resists the film to get 20 degraded easily.
An embodiment of the present invention provides coating materials that are biodegradable and non-toxic in nature. The coating materials of the invention are cheap, sustainable, environment friendly and transparent.
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In an embodiment of the present invention the coating materials/polymer film may be used for various packaging applications including food packaging. Because of its transparent nature and printability it may be used for attractive colorful packaging too.
In an embodiment of the present invention the coating compositions/polymer film 5 have antimicrobial properties.
In an embodiment of the present invention the coating compositions/polymer film are printable, water insoluble, compatible for use with the other packaging material, heat stable, sealable, printable, flexible and can be blended with other plastics. 10
A Biodegradable polymer composition or coating material according to the present invention can be used for various applications and should not be restricted to the exemplarily disclosed applications. For example also applications in the medical field, such as e.g. for sutures, and drug release matrices, or in the print industry are possible. 15
A composition of the present invention may be used for the production of various articles, such as e.g. molded articles and/or extruded articles. In particular, a composition according to the present invention may be used for preparing coatings and films, in particular extrusion coatings and extrusion films. As should be clear, a "molded article" (or "extruded article") may also be part of another 20 object, such as e.g. an insert in a container or a knife blade or fork insert in a corresponding handle.
A coating on the basis of a composition according to the present application may be applied on essentially any desired carrier material, such as e.g. paper, plastics, metals, wood, and composite materials comprising at least one of the above-25
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mentioned carrier materials, etc. When appropriate a coating comprising a composition according to the present invention can be applied on one or more intermediate layers present on a carrier material or can be provided with additional top or covering layers or coatings.
An application of a composition according to the present invention on a 5 Biodegradable carrier, such as e.g. paper, provides the advantage that both carrier, as well as the coating may be degraded upon exposition to water, and/or light, and/or soil bacteria. In particular, when the carrier is paper, the paper material may be submitted to re-pulping processes without the presence of essentially non-Biodegradable and thereby interfering plastic or wax coatings. For example food 10 service-ware, plates, cups, packaging, in particular ice cream packaging, cardboard boxes, trays made from paper or one of the other above-mentioned carrier materials can be coated with a coating, in particular an extrusion coating comprising a composition according to the present invention.
A film on the basis of a composition according to the present invention may be 15 applied on essentially any desired carrier material, such as e.g. paper, plastics, metals, wood, and composite materials comprising at least one of the above-mentioned carrier materials, etc. When appropriate, a coating comprising a composition according to the present invention can be applied on one or more intermediate layers present on the carrier material or can be provided with 20 additional top or covering layers or coatings.
Articles of the present invention produced on the basis of a film formulation, such as e.g. a blown film extrusion formulation or a flexible film formulation, are for example films for bags, such as trash bags, as well as grocery bags, or films for sealing containers, as well as films for an application on food service-ware, plates, 25
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cups, packaging, in particular ice cream packaging, cardboard boxes, trays made from paper or one of the other above-mentioned carrier materials.
In addition, the present invention provides a method of producing an article comprising a coating composition, said method comprising the steps of providing a coating composition comprising between 1.5 wt. % to 7.5 wt. % of polyvinyl 5 alcohol, and between 1.5 wt. % to 7.5 wt. % of starch, each on the basis of the total weight of the composition; and preparing a film or coating from said composition and optionally applying said film or coating on the article.
Processes for preparing coatings and films, such as dipping, spraying, brushing, painting, or extruding e.g. extrusion coating application, blown film extrusion, dip 10 forming, dip blow molding, dip molding, dip coating, doctor blade coating, and/or articles such as e.g. injection molding, profile extrusion and thermoform extrusion are processes known to a skilled person; Injection Molding--the process of forming a material by forcing it, in a fluid state and under pressure, through a runner system (sprue, runner, gates) into the cavity of a closed mold; Extrusion--a 15 process in which heated or unheated plastic is forced through a shaping orifice (a die) in one continuously formed shape, as in film, sheet, rod, or tubing; Blow Molding--a method of fabrication in which a heated parison is forced into the shape of a mold cavity by internal cavity pressure; Forming--a process in which the shape of plastic pieces such as sheets, rods, or tubes is changed to the desired 20 configuration; Thermoplastic--a plastic that repeatedly can be softened by heating and hardened by cooling through a temperature range characteristic of the plastic, and that in the softened state can be shaped by flow into articles by molding or extrusion.
Examples: 25
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The following examples illustrate the invention but are not limiting thereof. Method of preparing and forming the coating materials on a substrate
Example 1
Commercially available 5g starch and 5 g of polyvinyl alcohol were blended by dissolving them into 100 ml of commercially available neem extract prepared in 5 water medium. The solution was heated at 70°C and the solution was stirred by using a magnetic stirrer to form a homogeneous polymer solution. The homogeneous polymer solution was casted on petri-dishes and kept in an oven at 75°C.
Example 2 10
Commercially available 5g starch and 5g of polyvinyl alcohol were blended by dissolving them into 100 ml of commercially available neem extract prepared in water medium. 0.5g of citric acid and 0.25g sodium hypophosphite was added to the solution. The solution was heated at 80°C for 20 min with stirring to form a homogeneous polymer solution. 1g of maleic anhydride was added to the polymer 15 solution. The homogeneous polymer solution was casted on petri-dishes and kept in an oven at 75°C. The film formed was used as a food packaging film.
Example 3
Commercially available 3.5g starch and 6.5g of polyvinyl alcohol were blended by dissolving them into 100 ml of commercially available neem extract prepared 20 in water medium. 0.5g of citric acid and 0.25g sodium hypophosphite was added to the solution. The solution was heated at 75°C for 20 min with stirring to form a homogeneous polymer solution. 1g of maleic anhydride was added to the polymer solution. The homogeneous polymer solution was casted on petri-dishes and kept in an oven at 75°C to obtain a film. 25
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Example 4
Commercially available 2.5 g starch and 3.5g of polyvinyl alcohol were blended by dissolving them into 60 ml of commercially available neem extract prepared in water medium. 0.3g of citric acid and 0.15g sodium hypophosphite was added to the solution. The solution was heated at 75°C for 20 min with stirring to form a 5 homogeneous polymer solution. 0.6g of maleic anhydride was added to the polymer solution. The homogeneous polymer solution was casted on petri-dishes and kept in an oven at 75°C.
Experimental Results-
Experiments were conducted with different compositions of Starch, Polyvinyl 10 alcohol and antimicrobial agents to test the coating material obtained for tear strength, tensile strength, degradation and solubility in water.
Test No. 1-
5 g Starch and 5 g Polyvinyl alcohol were blended in a solution containing 0.5% of neem extract. A coating was prepared as per the method discussed above. The 15 resultant coating was tested for tear strength, tensile strength, degradation and solubility in water. The results are tabulated as test 1 in the table 1 given below.
Test No. 2 -
6.5 g Starch and 3.5 g Polyvinyl alcohol were blended in a solution containing 0.5% of neem extract. A coating was prepared as per the method discussed above. 20 The resultant coating was tested for tear strength, tensile strength, degradation and solubility in water. The results are tabulated as test 2 in the table 1 given below.
Test No. 3 -
3. 5 g Starch and 6.5 g Polyvinyl alcohol were blended in a solution containing 0.5% of neem extract. A coating was prepared as per the method discussed above. 25
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The resultant coating was tested for tear strength, tensile strength, degradation and solubility in water. The results are tabulated as test 3 in the table 1 given below.
Comparative example-
In comparison to the above compositions, tests were conducted with 10 g starch dissolved in 0.5% neem extract. A coating was prepared as per the method 5 discussed above but without Polyvinyl alcohol. The resultant coating was tested for tear strength, tensile strength, degradation and solubility in water. The results are tabulated as Comparative Example in the table 1 given below.
Table 1. 10
Example
Unit
Test 1
Test 2
Test 3
Comparative Example
Starch
Wt %
5
6.5
3.5
10
Polyvinyl alcohol
Wt %
5
3.5
6.5
0
Antimicrobial agent
Wt %
0.5%
0.5%
0.5%
0.5%
Properties
Tear strength
MPa
19.2
15.5
22.0
12.1
Tensile strength
MPa
29.5
27.9
32.7
23.4
Degradation
Time
15 days
9 days
30 days
7 days
Dissolution in water
Swells but does not dissolve
Swells but does not dissolve
Swells but does not dissolve
Swells but does not dissolve
Column (1) (2) and (3) relate to the composition of the present invention with different ranges of components.
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We Claim :
1. A coating material comprising
at least one biopolymer;
at least one synthetic polymer; and
at least one antimicrobial agent. 5
2. The coating material as claimed in claim 1, wherein the biopolymer is selected from natural and/or modified starch , the synthetic polymer is selected from polyvinyl alcohol, ethylene-vinyl acetate (EVA), vinyl chloride-vinyl acetate, N-vinylpyrrolidone-vinyl acetate, maleic anhydride-vinyl. 10
3. The coating material as claimed in claim 1, wherein the biopolymer is starch, the synthetic polymer is polyvinyl alcohol and the antimicrobial agent is neem extract.
4. A method of forming a coating material, the method comprising,
mixing at least one biopolymer, at least one synthetic polymer and at least 15 one antimicrobial agent to form a solution; and
heating the solution to obtain a polymer solution of the coating material.
5. The method of forming a coating material, the method comprising,
mixing at least one biopolymer, at least one synthetic polymer and at least one anti microbial agent to form a solution; 20
adding a crosslinking agent in the presence of an initiating agent to the above solution to form a
mixture; and
heating the mixture to obtain a polymer solution of the coating material.
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6.. The method as claimed in any of the preceding claim 4 or 5 further comprising adding a
compatibilizer to the polymer solution.
7. A method of forming a coating on a substrate, the method comprising applying the coating 5
material formed by the method as claimed in any of the preceding claim 4 or 5 on a substrate.
8. The method as claimed in claim 7 comprising applying the coating material on the substrate after adding a crosslinking agent to the coating material formed by the method as claimed in claim 4. 10
9. The coating material as claimed in any of the preceding claim, wherein the synthetic polymer is selected from polyvinyl alcohol, ethylene-vinyl acetate, or vinyl chloride-vinyl acetate, N-vinylpyrrolidone-vinyl acetate, maleic anhydride-vinyl acetate or a mixture thereof, preferably polyvinyl alcohol. 15
10. The coating material as claimed in any of the preceding claim, wherein the biopolymer is selected from natural and/or modified starch.
11. The coating material as claimed in any of the preceding claim, wherein the antimicrobial agent is selected from the group comprising of herbal extracts, bis-biguanide salts such as chlorhexidine digluconate, 20 chlorhexidine diacetate, chlorhexidine dihydrochloride, chlorhexidine diphosphanilate, rifampin, minocycline, silver compounds such as silver chloride, silver oxide, silver sulfadiazine, triclosan, octenidine dihydrochloride, quaternary ammonium compounds such as benzalkonium chloride, tridodecyl methyl ammonium chloride, didecyl 25
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dimethyl ammonium chloride, chloroallyl hexaminium chloride, benzethonium chloride, methylbenzethonium chloride, cetyl trimethyl ammonium bromide, cetyl pyridinium chloride, dioctyldimethyl ammonium chloride, iron-sequestering glycoproteins such as lactoferrin, ovotransferrin/conalbumin, cationic polypeptides such as protamine, 5 polylysine, lysozyme, surfactants such as SDS, Tween-80, surfactin, Nonoxynol-9 zinc pyrithione, broad-spectrum antibiotics such as quinolones, fluoroquinolones, aminoglycosides and sulfonamides, antiseptic agents such as iodine, methenamine, nitrofurantoin, validixic acid, phytochemicals such as citric acid, a plant extract or a combination 10 of different plant extracts, benzoic acid, sorbic acid, nisin, thymol, allicin, peroxides, imazalil, triclosan, benomyl, antimicrobial metal-ion exchange material, metal colloids, metal salts, anhydrides, and organic quaternary ammonium salts or mixtures thereof.
12. The coating material as claimed in any of the preceding claim, wherein the 15 synthetic polymer is in the range of 1.5 wt. % to 7.5 wt. % and the biopolymer is in the range of 1.5 wt. % to 7.5 wt. % of the total composition.
13. The coating material as claimed in any of the preceding claim, wherein the biopolymer is in the range of 2 wt. % to 7 wt. %, preferably 4 wt. % to 5 20 wt. % of the total weight of the material.
14. The coating material as claimed in any of the preceding claim, wherein the synthetic polymer is in the range of 2 wt. % to 7 wt. %, preferably 4 wt. % to 5 wt. % of the total weight of the material.
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15. The coating material as claimed in any of the preceding claim, wherein the biopolymer and the synthetic polymer solution is in a ratio from 1:4 to 4:1.
16. The coating material as claimed in any of the preceding claim, wherein the biopolymer and the synthetic polymer solution is in a ratio of 1:1.
17. The coating material as claimed in claim any of the preceding claim, 5 wherein the polyvinyl alcohol has a molecular weight of at least 2000 Da, preferably from 10000 Da. to 1000000 Da, more preferably up to 30,000 Da.
18. The method as claimed in any of the preceding claim 4 or 5, further comprising adding an alcohol selected from ethylene glycol, glycerol, 10 polyethylene glycol or sorbitol to the solution of biopolymer, synthetic polymer and antimicrobial agent.
19. The method as claimed in claim 5, wherein the crosslinking agent is selected from citric acid, a mixture of gluteraldehyde, sodium sulfate, sulphuric acid and HCl, epichlorohydrine, formaldehyde, preferably citric 15 acid.
20. The method as claimed in claim 5, wherein the initiating agent is sodium hypophosphite.
21. The method as claimed in claim 6, wherein the compatibilizer is selected from the group comprising of maleic anhydride, borax, butyl and adipate co 20 terephthalate or a mixture thereof, preferably maleic anhydride.