Description:FIELD OF THE INVENTION
[0001] The present invention relates to an antimicrobial thermoplastic polymer resin composition and the methods for making the same. Specifically, present invention relates to a built-in and safe-to-use antimicrobial thermoplastic polymer resin compositions comprising nano- or micro-sized antimicrobial additives, method for preparing the same, and articles comprising the same.

BACKGROUND OF THE INVENTION
[0002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
[0003] Thermoplastic polymer resins such as Polypropylene (PP) and Polyethylene (PE) are commodity polymers and are handled in hygiene-critical, high traffic environments such as food and healthcare industry. Thus, frequent touch combined with lapses in cleaning can expose the material to pathogens and may even result in cross contamination from surface to surface and surface to person. Specially in food and beverage packaging, pathogens such as gram-positive and gram-negative bacteria as well as yeasts and molds, adversely affect the color, texture, and nutritive value of food and beverage products and eventually make them non-edible.
[0004] Antimicrobial articles involve incorporation of antimicrobial agents in the polymer / plastic to impart antimicrobial activity and to keep product/article safe and to maintain its quality. Antimicrobial plastic prevents the penetration of undesirable pathogens and can be used to control/ inhibit microbial growth in packaged food thereby increasing the shelf life. Typical applications for antimicrobial plastic articles include food packaging; consumer products such as rotomoulded articles, injection moulded articles, blow moulded articles; medical devices; and any other article or apparatus in which human contact is expected.
[0005] CN216033010U discloses a multilayer film (9 layers) consisting of almost four layers of LDPE, one layer of LLDPE, Nano PET films, NanoTiO2 films and a ultraviolet – light reflection film formed by stacking a tantalum oxide and silicon oxide films. The LDPE used is sorbate, chitosan, amino acid silver, ethyl paraben modified films. The Purpose of LDPE – modified chitosan is to get antibacterial activity. The purpose of using UV films of Tantalum oxide and silicon dioxide and Nano TiO2 films is to absorb UV radiation at the required wave length and generate heat. All these 8-9 layers are bonded thermally.
[0006] JP 2022/176091A discloses the preparation of antimicrobial composition by mixing 1- 10 wt.% photo-catalyst particles (Oxides of Tantalum, Fe, Zn, Tu, Cr, Mo, Ge, Mn, Ni etc.), other metal particles (Ag, Cu, Pt in the form nitrates and other salts which are getting oxidized to metal when a reducing agents like vitamin C are added), aromatic compounds (plant extract such as camphor, terpeneol or like) and a solvent (water). The other metal particles (Ag from Ag Nitrate) are capable of releasing a metal ion having an antimicrobial effect. The aromatic compound contains a compound having an antibacterial and/or antifungal effect and fragrance for the whole of the antimicrobial composition.
[0007] There is a need to provide a composition and process for the production of a plastic material having antibacterial and/or antimicrobial properties, and to the product obtained using such material in the production process for manufacturing films, and objects with the same properties.
[0008] The present invention satisfies the existing needs, as well as others, and generally overcomes the deficiencies found in the prior art.

OBJECTS OF THE INVENTION
[0009] Objects of the present invention is to provide a polymer resin compositions and process for the production of a plastic article having antibacterial and/or antimicrobial properties and to improve the shelf life of fruits and vegetables.
[0010] An object of the present invention is to provide a a built-in and safe-to-use antimicrobial thermoplastic polymer resin compositions.
[0011] An object of the present invention is to provide antimicrobial thermoplastic polymer resins loaded with the nano- or micro-sized antimicrobial additives.
[0012] An object of the present invention is to provide a method of preparing antimicrobial thermoplastic polymer resins loaded with the nano- or micro-sized antimicrobial additives.
[0013] Another object of the present invention is to provide an article comprising the antimicrobial thermoplastic polymer resins loaded with the nano- or micro-sized antimicrobial additives.
[0014] Yet another object of the present invention is to a method of preparing the article comprising the antimicrobial thermoplastic polymer resins loaded with the nano- or micro-sized antimicrobial additives.

SUMMARY OF THE INVENTION
[0015] This summary is provided to introduce a selection of concepts in a simplified form that is further described below in the detailed description section. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.
[0016] Aspects of the present invention relates to an antimicrobial thermoplastic polymer resin composition and the methods for making the same. Specifically, present invention relates to a built-in and safe-to-use antimicrobial thermoplastic polymer resin composition comprising nano- or micro-sized antimicrobial additives, method for preparing the same, and articles comprising the same.
[0017] In one aspect, the present invention provides a thermoplastic polymer resin composition, comprising (a) a thermoplastic polymer; (b) an antimicrobial additive; and (c) optionally, one or more additives.
[0018] In one aspect, the present invention provides a thermoplastic composition, comprising (a) 1 wt % to about 99.9 wt % of a thermoplastic polymer; (b) 1 wt % to about 99 wt % of antimicrobial additive; and (c) optionally, 0.01 wt % to about 0.5 wt % of one or more additives.
[0019] In one aspect, the present invention provides a thermoplastic composition, comprising (a) 99 wt % to about 99.9 wt % of a thermoplastic polymer; (b) 0.1 wt % to about 1 wt % of antimicrobial additive; and (c) optionally, 0.01 wt % to about 0.5 wt % of one or more additives.
[0020] In one aspect, the present invention provides an antimicrobial thermoplastic polymer resin composition, said composition comprising (a) a thermoplastic polymer matrix comprising a polypropylene (PP), polyethylene (PE) or a combination thereof in an amount of 99-99.9 wt%; (b) an antimicrobial additive component in an amount of 0.1-1 wt%; and (c) optionally, an additive selected from the group consisting of a thermal stabilizer, an UV stabilizer, anti-oxidant, a lubricant, a flame retardant agent, a smoke suppressor agent, a pigment, and combinations thereof in an amount of 0.01 wt% to 0.5 wt%.
[0021] In another aspect, the present invention provides a method of preparing the antimicrobial thermoplastic polymer resin composition by melt blending of (a) a thermoplastic polymer comprising a polypropylene (PP), polyethylene (PE) or a combination thereof; (b) antimicrobial additive component selected from nanoparticles or microparticles of Tantalum, Zinc Oxide, Copper, Silver, and combinations thereof at concentration from 250 – 2500 ppm; and (c) optionally, an additive selected from the group consisting of a thermal stabilizer, an UV stabilizer, anti-oxidant, a lubricant, a flame retardant agent, a smoke suppressor agent, a pigment, and combinations thereof. In this process, polypropylene, antimicrobial additive and other additives were dry blended in high speed mixer under nitrogen at room temperature. These compositions were melt mixed in Banbury mixer or Single Screw Extruder or Twin Screw Extruder by two different methods. (1) Direct melt blending and extrusion in (a) single screw extruder having L/D ratio of 25/1, Diameter – 25 mm by variation of temperature profile from 160 – 210°C, RPM 20 – 100 and in (b) Twin Screw Extruder having L/D ratio of 40/1, Screw diameter – 30 mm with five heating zones by variation of temperature profile 160 – 230°C, RPM: 50 – 150 and extruded into granules. (2) Making Master Batches (MB) in Banbury mixer by variation of Antimicrobial additive concentration (1 – 10 wt%.), Screw RPM 20 – 100, Mixing time 5 min to 60 min and temperature from 160 – 210°C. The extrudates were cut into small granules. These granules were further diluted with polypropylene (a) in Banbury mixer again or in (b) Single screw extruder (c) Twin Screw Extruder to get the required antimicrobial concentration of 250 – 2500 ppm in the final compositions.
[0022] In yet another aspect, the present invention provides a method for preparing an article having antimicrobial property, said method comprising: (a) providing a thermoplastic polymer comprising a polypropylene (PP), polyethylene (PE) or a combination thereof; (b) antimicrobial additive component selected from nanoparticles or microparticles of Tantalum, Zinc Oxide, Copper, Silver, and combinations thereof at concentration from 250 – 2500 ppm; (c) optionally, an additive selected from the group consisting of a thermal stabilizer, an UV stabilizer, anti-oxidant, a lubricant, a flame retardant agent, a smoke suppressor agent, a pigment, and combinations thereof to form a composition; and (d) Melt-blending and extrusion in Single Screw Extruder / Twin Screw Extruder into granules (e) Cast film extrusion of extruded granules was carried out in in Single Screw Extruder cast film unit (Dr Collins) with a L/D – 25/1, Dia – 25 mm, Temperature profile 180 – 210°C, RPM 30 – 60, Roller Speed 2 – 10, into cast films with desired shape and dimensions. The antimicrobial films / sheets were also made by using compression moulding machine at a temperature of 160 – 190oC, pressure – 30 bar for 10 – 30 min to get required shape and size.
[0023] In yet another aspect, the Antimicrobial properties were evaluated by Bacterial Reduction test as per ASTM E 2180-07 for antimicrobial thermoplastic polymer resin cast films containing Tantalum, Zinc oxide, Cu, Ag and their bimetallic combinations. Antimicrobial films showed a bacterial reduction of upto 99.99% compared to no reduction in pristine PP films.
[0024] Various objects, features, aspects and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS:
[0025] The following drawings form part of the present specification and are included to further illustrate aspects of the present disclosure. The disclosure may be better understood by reference to the drawings in combination with the detailed description of the specific embodiments presented herein.
[0026] FIG. 1 provides the FE-SEM images of (a) Tantalum (b) Zinc oxide (c) Copper (d) Silver.
[0027] FIG. 2 provides process flow for making antimicrobial films
[0028] FIG. 3 provides the image of Antimicrobial Cast Films of Polypropylene prepared according to the embodiments of the present invention
[0029] FIG. 4 provides the image of Antimicrobial Polypropylene films produced by compression moulding according to the embodiments of the present invention
[0030] FIG. 5 provides the image of Shelf-life study of vegetables using Antimicrobial polypropylene films

DETAILED DESCRIPTION OF THE INVENTION
[0031] The following is a detailed description of embodiments of the disclosure. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure.
[0032] All publications herein are incorporated by reference to the same extent as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.
[0033] Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.
[0034] In some embodiments, numbers have been used for quantifying weight percentages, ratios, and so forth, to describe and claim certain embodiments of the invention and are to be understood as being modified in some instances by the term “about.” Accordingly, in some embodiments, the numerical parameters set forth in the written description and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by a particular embodiment. In some embodiments, the numerical parameters should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of some embodiments of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as practicable. The numerical values presented in some embodiments of the invention may contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements.
[0035] Various terms as used herein are shown below. To the extent a term used in a claim is not defined below, it should be given the broadest definition persons in the pertinent art have given that term as reflected in printed publications and issued patents at the time of filing.
[0036] As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
[0037] Unless the context requires otherwise, throughout the specification which follow, the word “comprise” and variations thereof, such as, “comprises” and “comprising” are to be construed in an open, inclusive sense that is as “including, but not limited to.”
[0038] The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein.
[0039] All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.
[0040] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified.
[0041] The description that follows, and the embodiments described therein, is provided by way of illustration of an example, or examples, of particular embodiments of the principles and aspects of the present disclosure. These examples are provided for the purposes of explanation, and not of limitation, of those principles and of the disclosure.
[0042] It should also be appreciated that the present disclosure can be implemented in numerous ways, including as a system, a method or a device. In this specification, these implementations, or any other form that the invention may take, may be referred to as processes. In general, the order of the steps of the disclosed processes may be altered within the scope of the invention.
[0043] The headings and abstract of the invention provided herein are for convenience only and do not interpret the scope or meaning of the embodiments.
[0044] The following discussion provides many example embodiments of the inventive subject matter. Although each embodiment represents a single combination of inventive elements, the inventive subject matter is considered to include all possible combinations of the disclosed elements. Thus, if one embodiment comprises elements a, b, and c, and a second embodiment comprises elements b and d, then the inventive subject matter is also considered to include other remaining combinations of a, b, c, or d, even if not explicitly disclosed.
[0045] Unless the context requires otherwise, throughout the specification which follow, the expression “nanoparticles” and variations thereof, such as, “nano sized particles” and “nano shaped particles” relate mainly to the “nanoparticles”.
[0046] While a particular form of the invention has been illustrated and described, it will be apparent that various modifications can be made without departing from the spirit and scope of the invention.
[0047] Embodiments of the present invention relates to an antimicrobial thermoplastic polymer resin composition and the methods for making the same. Specifically, present invention relates to a built-in and safe-to-use antimicrobial thermoplastic polymer resin composition comprising nano- or micro-sized antimicrobial additives, method for preparing the same, and articles comprising the same.
[0048] In an embodiment of the present invention, the antimicrobial activity comprise antibacterial (bactericidal, bacteriostatic) activity, antifungal activity, antiviral (virucidal, virustatic) activity, or a combination thereof. Preferably, antibacterial activity
[0049] In one embodiment, the present invention provides a thermoplastic polymer resin composition, comprising (a) a thermoplastic polymer; (b) an antimicrobial additive; and (c) optionally, one or more additives.
[0050] In an embodiment of the present invention, the thermoplastic polymer component is selected from but not limited to a polycarbonate (PC), Polylactic acid (PLA), polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polyphenylene oxide (PPO), polyetherimide (PEI), or a combination thereof. Preferably, polyethylene (PE), polypropylene (PP), and combinations thereof.
[0051] In an embodiment of the present invention, the antimicrobial additive component is nanoparticles or microparticles of metals or metals oxides selected from but not limited to Tantalum microparticles, Zinc Oxide, Copper, Silver, and combinations thereof
[0052] In an embodiment of the present invention, the antimicrobial additives have average sizes ranging in the nanometer scale. In some embodiments, the nano sized antimicrobial additives may have an average particle size of at least about 1 nm, 10 nm, 50 nm, and 100 nm. The diameter of microparticles have an average size of 1 µm, 50 µm, 100 µm, 500 µm and 1000 µm. The diameter of nanoparticles can range from any of the minimum values described above to any of the maximum values described above, for example from 1 nm to 10 nm, 10 nm to 50 nm, 50 nm to 100 nm. Most preferably, the size of the antimicrobial additives range from about 40 to 100 nm. The diameter of microparticles can range from any of the minimum values described above to any of the maximum values described above, for example from 1 µm to 50 µm, 50 µm to 100 µm, 100 to 500 µm, and 500 µm to 1000 µm. Most preferably, the size of the antimicrobial additives range from about 40 µm to 100 µm.
[0053] In an embodiment of the present invention, the additive component is selected from but not limited to a thermal stabilizer, an UV stabilizer, anti-oxidant, a lubricant, a flame retardant agent, a smoke suppressor agent, a pigment, and any combinations thereof.
[0054] In an embodiment of the present invention, the thermoplastic polymer component is present in an amount from about 1 wt % to about 99.9 wt %. In a still further embodiment, the thermoplastic polymer component is present in an amount from about 90 wt % to about 99.9 wt %. In a yet further embodiment, the thermoplastic polymer component is present in an amount from about 99 wt % to about 99.9 wt %.
[0055] In an embodiment of the present invention, the antimicrobial additive component is present in an amount from about 0.1 wt % to about 99 wt %. In a still further embodiment, the antimicrobial additive is present in an amount from about 0.1 wt % to about 10 wt %. In a yet further embodiment, the antimicrobial additive is present in an amount from about 0.1 wt % to about 1 wt %.
[0056] In another embodiment of the present invention, the antimicrobial additive component is present in a concentration of 250 – 2500 ppm. For example, 250, 300, 350, 400, 500, 600, 700, 800, 900, 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900, 2000, 2100, 2200, 2300, 2400, or 2500 ppm.
[0057] In an embodiment of the present invention, the other additive component may be present in an amount from about 0.1 wt % to about 10 wt %. In a still further embodiment, the additive is present in an amount from about 0.1 wt % to about 1 wt %. In a yet further embodiment, the additive is present in an amount from about 0.10 wt % to about 0.5 wt %.
[0058] In one embodiment, the present invention provides a thermoplastic composition, comprising (a) 99 wt % to about 99.9 wt % of a thermoplastic polymer; (b) 0.1 wt % to about 1 wt % of antimicrobial additive; and (c) optionally, 0.01 wt % to about 0.5 wt % of one or more additives.
[0059] In one embodiment, the present invention provides an antimicrobial thermoplastic polymer resin composition, said composition comprising (a) a thermoplastic polymer matrix comprising a polypropylene (PP), polyethylene (PE) or a combination thereof in an amount of 99-99.9 wt%; (b) an antimicrobial additive component in an amount of 0.1-1 wt%; and (c) optionally, an additive selected from the group consisting of a thermal stabilizer, an UV stabilizer, anti-oxidant, a lubricant, a flame retardant agent, a smoke suppressor agent, a pigment, and combinations thereof in an amount of 0.1 wt.% to 0.5 wt.%.
[0060] In an embodiment of the present invention, the antimicrobial thermoplastic polymer resin composition can be prepared by various methods known in the art. The compositions of the present invention can be blended with the aforementioned ingredients by a variety of methods involving intimate admixing of the materials with any additional additives desired in the formulation. Because of the better mixing of polymer resin, additives and antimicrobial additives, melt blending equipment with commercial polymer processing facilities and melt processing methods can be used to get better homogeneity.
[0061] In one embodiment, the present invention provides a method of preparing the antimicrobial thermoplastic polymer resin composition by melt blending of (a) a thermoplastic polymer comprising a polypropylene (PP), polyethylene (PE) or a combination thereof; (b) antimicrobial additive component selected from nanoparticles or microparticles of Tantalum microparticles, Zinc Oxide, Copper, Silver, and combinations thereof at concentration from 250 – 2500 ppm; and (c) optionally, an additive selected from the group consisting of a thermal stabilizer, an UV stabilizer, anti-oxidant, a lubricant, a flame retardant agent, a smoke suppressor agent, a pigment, and combinations thereof. In this process, polypropylene, antimicrobial additive and other additives are dry blended in high speed mixer under nitrogen at room temperature. These compositions are then melt mixed in Banbury mixer or Single Screw Extruder or Twin Screw Extruder by three different methods. (1) Direct melt blending and extrusion in (a) single screw extruder having L/D ratio of 25/1, Diameter – 25 mm by variation of temperature profile from 160 – 210°C, RPM 20 – 100 and in (b) Twin Screw Extruder having L/D ratio of 40/1, Screw diameter – 30 mm with five heating zones by variation of temperature profile 160 – 230°C, RPM: 50 – 150 and extruded into granules. (2) Making Master Batches (MB) in Banbury mixer by variation of Antimicrobial additive concentration (1 – 10 wt%.), Screw RPM 20 – 100, Mixing time 5 min to 60 min and temperature from 160 – 210°C. The extrudates are cut into small granules. These granules are further diluted with polypropylene (a) in Banbury mixer again or in (b) Single screw extruder (c) Twin Screw Extruder to get the required antimicrobial concentration of 250 – 2500 ppm in the final compositions.
[0062] In one embodiment, the present invention provides a method for preparing an article having antimicrobial property, said method comprising: (a) providing a thermoplastic polymer comprising a polypropylene (PP), polyethylene (PE) or a combination thereof; (b) antimicrobial additive component selected from nanoparticles or microparticles of Tantalum microparticles, Zinc Oxide, Copper, Silver, and combinations thereof at concentration from 250 – 2500 ppm; (c) optionally, an additive selected from the group consisting of a thermal stabilizer, an UV stabilizer, anti-oxidant, a lubricant, a flame retardant agent, a smoke suppressor agent, a pigment, and combinations thereof to form a composition; and (d) Melt-blending and extrusion in Single Screw Extruder / Twin Screw Extruder into granules (e) Cast film extrusion of extruded granules was carried out in in Single Screw Extruder cast film unit with a L/D – 25/1, Dia – 25 mm, Temperature profile 180 – 210°C, RPM 30 – 60, Roller Speed 2 – 10, into cast films with desired shape and dimensions. The antimicrobial films or sheets were also made by using compression moulding machine at a temperature of 160 – 190°C, pressure – 30 bar for 10 – 30 min to get required shape and size.
[0063] In an embodiment, the extrusion is effected by profile extrusion, injection moulding, blow moulding, blown film, film casting, spinning and over moulding.
[0064] In an embodiment, the melt-extrusion process is effected via a single screw extruder, twin-screw extruder, a Banbury mixer or other heat-assisted blend process.
[0065] In an embodiment, the moulding / extrusion article is selected from the group consisting of moulded articles, films, sheets, fiber, composite, solid articles, tube articles, or a combination thereof.
[0066] In an embodiment, the Antimicrobial properties were evaluated by Bacterial Reduction test (ASTM E 2180-07) for Antimicrobial polypropylene cast films containing Tantalum, Zinc oxide, Cu and Silver or their combinations. Antimicrobial films showed a bacterial reduction of upto 99.99% compared to no reduction in pristine PP films.
[0067] In another embodiment, the antimicrobial agents present in PP films besides acting as antimicrobial agents also acted as Nucleating agents by increasing the crystallization temperature and formation of new melting peak in addition to regular melting peak of isotactic polypropylene. The antimicrobial agents ZO and Cu showed ß-nucleation in addition to a-nucleation.
[0068] While the foregoing description discloses various embodiments of the disclosure, other and further embodiments of the invention may be devised without departing from the basic scope of the disclosure. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.
[0069] Materials and Characterization
Materials: Polypropylene homopolymer (MFI: 12 g/10 min, Density: 0.9 g/cm3), Tantalum powder (45 microns, 99.9% pure), Zinc oxide nanoparticles (APS<100 nm), Copper nanoparticles (60-80 nm, 99.9% pure), Silver nanoparticle (<90nm, 99.9% pure), Copper powder (APS~45 micron).
Polypropylene – PP; Tantalum powder – Ta; Zinc oxide nanoparticles – ZONP; Copper nanoparticles – CuNP; Silver nanoparticles – AgNP; Copper powder – CP.
[0070] Morphological analysis
The surface morphology of nanoparticles and microparticles was observed with a field-emission scanning electron microscope (JSM 7800, M/s. Jeol, Japan). Prior to the analysis, the specimens were coated with carbon using a Carbon Coater, M/s. Jeol, Japan. Elemental analysis was performed using JSM 7800, M/s. Jeol equipped with Oxford detectors for energy dispersive X-ray spectroscopy (EDS).
The morphology of different antimicrobial agents was studied by FE-SEM as given in FIG. 1. The tantalum powder is having flake morphology, zinc oxide nanoparticles are having rod shaped morphology, silver nanoparticles and copper nanoparticles are having spherical shape.
[0071] Antimicrobial study
Anti-microbial study for PP Antimicrobial films were done according to ASTM E-2180. The PP Antimicrobial films prepared are having a dimension of 3cm x 3cm with thickness less than 8mm. Tables 5-8.
[0072] Melt Flow Index (MFI)
MFI, expressed in g/10 min was determined using a melt flow indexer (Model CEAST MF20, M/s. Instron, UK) at 230°C with a load of 2.16 kg according to ASTM D1238. The MFI values reported are average of 10 measurements for each prepared composition. Table 9.
[0073] Differential Scanning Calorimetry (DSC)
DSC analysis of Antimicrobial polypropylene compositions carried under nitrogen (Tables 10-11)
[0074] Migration Study
Migration testing was performed as per ISO 9845:1998 for compression moulded films. Migration studies of different antimicrobial agents present in the films were studies against acidic stimulant i.e. distilled water having 3 wt.% acetic acid at 40oC & for 10 days. Tables 12-13.
[0075] EXAMPLES
The present disclosure is further explained in the form of following examples. However, it is to be understood that the foregoing examples are merely illustrative and are not to be taken as limitations upon the scope of the invention. Various changes and modifications to the disclosed embodiments will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the scope of the invention.
EXAMPLE 1
1. Preparation of Antimicrobial Polypropylene Compositions:
Various antimicrobial additives like Tantalum (Ta), Zinc oxide (ZO), Copper (Cu) and Silver (Ag) with a concentration ranging from 0.025 wt % to 10 wt % were dispersed in acetone with the help of probe sonication machine for 30 – 60 minutes and dry blended with polypropylene and further mixed for 20 – 30 minutes in a high-speed mixer. The acetone solvent was removed by drying at 60°C for 1 hr. In a similar way polyethylene and polypropylene / polyethylene combination compositions were made.
EXAMPLE 2
Preparation of Antimicrobial Polypropylene Masterbatches
Antimicrobial polypropylene masterbatches with different antimicrobial agents like Ta, Cu, ZO, Ag having different concentrations (1-10 wt %) were prepared in Banbury batch mixer. The antimicrobial agents were mixed with polypropylene at 190oC – 230oC and 40 - 100 rpm for 5 - 20 minutes. The antimicrobial masterbatches prepared were taken out from Banbury mixer, dried in oven at 80 °C for about 3 hours prior to dilution. Antimicrobial masterbatches of PE and PP / PE polymers were produced in a similar by replacing PP with these polymers as above. Details given in Table 1-4.
EXAMPLE 3
Extrusion of Antimicrobial Polypropylene Compositions
The above antimicrobial compositions & Master batches were further diluted to antimicrobial additive concentration of 250 – 2500 ppm with their respective polypropylene, polyethylene or combination of them were extruded in a (a) Single Screw Extruder having screw diameter of 25 mm, L/D of 25/1 and equipped with five heating zones. The temperature profile in the extruder was maintained from 160 to 210°C, Screw RPM - 10 and 100 rpm. (b) co-rotating twin-screw extruder having screw diameter of 30 mm, L/D of 40/1 and equipped with five heating zones.
Extruded strands were cooled in air or by passing it through a water bath maintained at 25°C with continuous water circulation and pelletized subsequently. Obtained pellets were dried in oven at 80°C for about 3 hours.
EXAMPLE 4
Preparation of Antimicrobial Polypropylene cast films
Cast film preparation was performed on a cast film extruder having screw diameter of 25 mm, L/D of 25/1 and equipped with 11 heating zones. The Antimicrobial PP granules were fed into the hopper and the temperature profile was maintained 180 - 210 °C from feed zone to die zone. The extruder screw speed was set 50-60 RPM and roller speed was maintained 2.5-3.5. In a similar way, cast film of PE were made by variation of temperature from 200-260 °C from feed zone to the die zone. The cast films rolls produced were uniform and having thickness in range of 60-80 microns (FIG. 3)
EXAMPLE 5
Preparation of Antimicrobial PP Compression moulded sheets
The extruded granules were first melted by bringing it in contact with the hot platens (0 bar) for 15 min before compression moulding at 190°C and pressure 30 bar for 10 min and then cooled to room temperature under pressure. The compression moulded sheets obtained are given in FIG. 4.

Table 1: Antimicrobial compositions of PP with Tantalum powder prepared by Masterbatch Addition
Sr. No PP with Ta Compositions PP
(gm) Ta-MB
(gm) Ta
(ppm)
1 PP 50 0 0
2 Ta-PP-0.025 48.75 1.25 250
3 Ta-PP-0.05 47.5 2.5 500
4 Ta-PP-0.1 45 5 1000
5 Ta-PP-0.25 37.5 12.5 2500

Table 2: Antimicrobial Compositions of PP with Zinc Oxide nanoparticles prepared by Masterbatch Addition
Sr. No PP / ZONP Compositions PP
(gm) ZONP-MB
(gm) ZONP
(ppm)
1 PP 50 0 0
2 ZONP-PP-0.025 48.75 1.25 250
3 ZONP-PP-0.05 47.5 2.5 500
4 ZONP-PP-0.1 45.0 5.0 1000
5 ZONP-PP-0.25 37.5 12.5 2500

Table 3: Antimicrobial Compositions of PP with Copper nanoparticles & Silver nanoparticles prepared by masterbatch addition
Sr. No PP / CuNP Compositions PP
(gm) CuNP-MB
(gm) CuNP
(ppm)
1 PP 50 0 0
2 CuNP-PP-0.05 47.5 2.5 500
3 AgNP-PP-0.05 47.5 2.5 500

Table 4: Antimicrobial PP Compositions of PP with Bimetals
Sr. No. PP with Bimetallic Compositions Polypropylene (gm) Bimetal -MB
(gm) Bimetals
(ppm)
1 PP 50 0 0
2 ZONP-Ta-PP-0.05 703 37 500
3 ZONP-AgNP-1PP-0.05 760 40 500

Table 5: Bacterial reduction in Antimicrobial PP films with Tantalum against S. Aureus and K. Pneumoniae
Sr. No. PP with Ta compositions Antibacterial activity against Gram positive bacteria
(S. aureus)
(%) Antibacterial activity against Gram negative bacteria
(K. pneumoniae)
(%)
1 PP No reduction No reduction
2 Ta-PP-0.025 99.05 98.93
3 Ta-PP-0.05 98.85 93.39
4 Ta-PP-0.1 99.94 98.98
5 Ta-PP-0.25 98.93 97.55
6 Ta-PP-0.05* 99.99 99.99
* cast extrusion film
Table 6: Bacterial reduction in Antimicrobial PP films with ZO against S. Aureus and K. pneumoniae
Sr. No. PP with ZONP Compositions Antibacterial activity against Gram positive bacteria
(S. aureus)
(%) Antibacterial activity against Gram negative bacteria
(K. pneumoniae)
(%)
1 PP No reduction No reduction
2 ZONP-PP-0.025 99.05 98.93
3 ZONP-PP-0.05 99.26 99.21
4 ZONP-PP-0.1 99.99 99.99
5 ZONP-PP-0.25 99.09 98.45
6 ZONP-PP-0.05* 99.99 99.99
* cast extrusion film

Table 7: Bacterial reduction in Antimicrobial PP films with bimetallic agents against S. Aureus and K. Pneumoniae
Sr. No. PP with Bimetallic Compositions Antibacterial activity against Gram positive bacteria
(S. aureus)
(%) Antibacterial activity against Gram negative bacteria
(K. pneumoniae)
(%)
1 PP No reduction No reduction
2 ZONP-Ta-PP-0.05 99.99 99.45
3 ZONP-AgNP-PP-0.05 99.99 99.28

Table 8: Bacterial reduction in Antimicrobial PP films with Copper & Silver Nanoparticles against S. Aureus and K. pneumoniae
Sr. No. PP with Cu & Ag Compositions Antibacterial activity against Gram positive bacteria
(S. aureus) (%) Antibacterial activity against Gram negative bacteria
(K. pneumoniae) (%)
1 PP No reduction No reduction
2 CuNP-PP-0.05 99.5 99.71
3 AgNP-PP-0.05 99.99 99.99

Table 9: MFI values of Polypropylene Compositions with Antimicrobial Additives
Sr. No. PP with Ta / ZO / Cu / Ag compositions MFI (g/10 min)
1 PP 13.86
2 Ta-PP-0.025 14.13
3 Ta-PP-0.05 14.13
4 Ta-PP-0.1 14.3
5 Ta-PP-0.25 15.49
6 ZONP-PP-0.025 15.23
7 ZONP-PP-0.05 14.33
8 ZONP-PP-0.1 14.42
9 ZONP-PP-0.25 15.37
10 ZONP-Ta-PP-0.05 14.29
11 ZONP-AgNP-PP-0.05 13.73
12 CuNP-PP-0.05 14.28
13 AgNP-PP-0.05 13.88

Table 10: DSC analysis of Antimicrobial PP with Copper powder
Sr. No. PP with Copper Powder Compositions Tm
(°C) Hm
(J/g) Tc
(°C) Hc
(J/g) %Xc
1 PP 164.7 101.2 112.6 99.1 47.8
2 CP-PP-10 165.3 79.6 123.5 85.1 41.1
3 CP-PP-5 165.4 75.3 123.1 82.8 40.0

Table 11: DSC analysis of Antimicrobial PP with ZONP & CuNP compositions
Sr. No. PP with ZO / Cu Compositions Tm1 (°C) Tm2 (°C) Hm (J/g) Hm1 (J/g) Tc
(°C) Hc (J/g) % Xc
1 PP 164.7 - 101.2 - 112.6 99.1 47.87
2 ZONP-PP-0.25 164.9 148.9 40.5 3.56 116.6 94.9 45.8
3 CuNP-PP-0.25 164.3 148.9 53.5 2.17 117.2 103.0 49.7
4 CuNP-PP-0.05 168.7 150.0 50.3 1.4 116.1 98.5 47.6

DSC studies (Tables 10 - 11) of Antimicrobial PP compositions with with Copper powder, Cu nanoparticles, ZO nanoparticles showed an increase in crystallization temperature (Tc) from 113 to 123oC. This analysis also showed two melting peaks in the range of 165oC – 169oC (for ?- nucleation) & 149oC - 150oC (for ?- nucleation) indicating the formation B nucleation in addition to ?-nucleation. This phenomenon clearly indicated that the Antibacterial agents like ZO & Cu particles playing dual role (a) Antibacterial agents and as ? - nucleating agents in polypropylene matrix.
Table 12: Migration studies of Antimicrobial PP films containing Ta / ZO / Cu and Ag in distilled water
Sr. No. PP with Ta / ZO / Cu / Ag compositions Max. Migration
(mg/m3) Test Result
(mg/m3)
1 PP 10 1.2
2 Ta-PP-0.05 10 0.95
3 ZONP-PP-0.05 10 1.1
4 CuNP-PP-0.05 10 1.05
5 AgNP-PP-0.05 10 1.3

Table 13: Migration studies of Antimicrobial PP films containing Ta / ZO / Cu and Ag in 3 wt.% acetic acid
Sr. No. PP with Ta / ZO / Cu / Ag compositions Max. Migration
(mg/m3) Test Result
(mg/m3)
1 PP 10 2.2
2 Ta-PP-0.05 10 2.45
3 ZONP-PP-0.05 10 3.1
4 CuNP-PP-0.05 10 3.35
5 AgNP-PP-0.05 10 3.05

Shelf life of fruits and Vegetables
Antimicrobial PP films containing different metal and metal oxides like Ta, Cu, Ag, ZO were tested for shelf life of fruits and vegetables. The packaged vegetables were observed for 30 days. No growth of fungi / mold / microorganisms observed for 7 days on chillies. While tomatoes were fresh for more than 15 days (FIG. 5).
, Claims:1. An antimicrobial thermoplastic polymer resin composition, said composition comprising
(a) a thermoplastic polymer matrix comprising a polypropylene (PP), polyethylene (PE) or a combination thereof in an amount of 99-99.9 wt%;
(b) an antimicrobial additive component in an amount of 0.1-1 wt%; and
(c) an additive selected from the group consisting of a thermal stabilizer, an UV stabilizer, anti-oxidant, a lubricant, a flame retardant agent, a smoke suppressor agent, a pigment, and combinations thereof in an amount of 0.01-0.5% wt%
2. The composition as claimed in claim 1, wherein the antimicrobial additive component is nanoparticles or microparticles of Tantalum, Zinc Oxide, Copper, Silver, and combinations thereof at a concentration of 250 – 2500 ppm.
3. The composition as claimed in claim 1, wherein the antimicrobial additive has an average particle size of 60 nm to 45µm.
4. The composition as claimed in claim 1 exhibits ?-nucleation with Tm1 of 149oC and ?-nucleation with Tm2 of 169oC with an increase in crystallization temperature of 123oC.
5. A method of preparing the antimicrobial thermoplastic polymer resin composition as claimed in anyone of claims 1-3 by melt blending and extrusion, said method comprising:
(a) providing a thermoplastic polymer;
(b) providing antimicrobial additive component; and
(c) optionally, providing an additive selected from the group consisting of a thermal stabilizer, an UV stabilizer, anti-oxidant, a lubricant, a flame retardant agent, a smoke suppressor agent, a pigment, and combinations thereof.
(d) preparing a masterbatch composition by mixing components from (a) and (b) & (c) to form a mixture;
(e) melt-extrusion of said mixture into granules, followed by dilution with the thermoplastic polymer; and
(f) repeating the steps (a) – (e) till the antimicrobial concentration of 250 – 2500 ppm in the antimicrobial thermoplastic polymer resin composition is obtained.
6. The method as claimed in claim 5, wherein the melt-extrusion and melt mixing is carried out in a single screw extruder, a twin-screw extruder, and Banbury mixer.
7. The method as claimed in claim 5, wherein the extrusion effected in the single screw extruder having (i) L/D ratio of 25/1, (ii) screw diameter of 25 mm, (iii) temperature of 160 – 210°C and (iv) screw RPM of 20 – 100.
8. The method as claimed in claim 5, wherein the extrusion effected in the Twin screw extruder having (i) L/D ratio of 40/1, (ii) screw diameter of 30 mm, (iii) temperature of 160 – 230°C and (iv) screw RPM of 50 – 150.
9. The method as claimed in claim 5, wherein the melt mixing is carried out in the Banbury mixer having (i) temperature of 160 – 210°C, (ii) mixing time of 5-60 min, and (iii) screw RPM of 20 – 100.
10. The method as claimed in claim 5 further comprising the step of moulding the antimicrobial thermoplastic polymer resin composition of step (f) by compression moulding at a temperature of 160 – 190°C and a pressure of 30 bar for 10 – 30 min.
11. A method of preparing an antimicrobial article comprising,
(a) providing a thermoplastic polymer matrix comprising a polypropylene (PP), polyethylene (PE) or a combination thereof in an amount of 90-99.9 wt%;
(b) providing antimicrobial additive component selected from nanoparticles or microparticles of Tantalum microparticles, Zinc Oxide, Copper, Silver, and combinations thereof in an amount of 0.1-1 wt%; and
(c) providing an additive selected from the group consisting of a thermal stabilizer, an UV stabilizer, anti-oxidant, a lubricant, a flame retardant agent, a smoke suppressor agent, a pigment, and combinations thereof in an amount of 0.01-0.5% wt%
(d) preparing the antimicrobial thermoplastic polymer resin composition by the method as claimed in claim 5;
(e) casting the antimicrobial thermoplastic polymer resin composition from step (d) by using a Single Screw Extruder unit having (i) a L/D ratio of 25/1, (ii) screw diameter of 25 mm, (iii) ttemperature of 180 – 210°C, (iv) screw RPM of 30 – 60, and (v) Roller Speed of 2 – 10.
12. The antimicrobial article as claimed in claim 11, wherein the article is selected from the group consisting of moulded articles, films, sheets, fiber, composite, solid articles, tube articles, or a combination thereof.
13. The antimicrobial article as claimed in claim 12, wherein the antimicrobial article effects a microorganism reduction of 92 to 99.99% as per ASTM E-2180-07.