WO2020252566A1

WO2020252566A1 - Antimicrobial plastic blends, processes for the preparation thereof and uses thereof

Info

Publication number: WO2020252566A1
Application number: PCT/CA2020/050800
Authority: WO
Inventors: Minh Tan TON-THAT; Hongbo Li; Chi Woon Leung; Edmond Lam
Original assignee: National Research Council Of Canada
Priority date: 2019-06-21
Filing date: 2020-06-11
Publication date: 2020-12-24

Abstract

The present application relates to antimicrobial plastic blends comprising a quaternary ammonium modified lignin-containing material wherein lignin phenols are in the anionic form and a dispersing plastic (e.g. polypropylene), to processes for preparing such blends and to uses of such blends, for example, as a surface for killing and/or inhibiting the growth of a microbe. The present application also relates to plastic compounds for use in forming such antimicrobial plastic blends as well as processes for preparing such plastic compounds.

Description

TITLE: ANTIMICROBIAL PLASTIC BLENDS, PROCESSES FOR THE PREPARATION THEREOF AND USES THEREOF

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims the benefit of priority from co-pending U.S. provisional application no. 62/864,592 filed on June 21 , 2019, the contents of which are incorporated herein by reference in their entirety.

FIELD

[0002] The present application relates to antimicrobial plastic blends, to processes for preparing such blends and to uses of such blends, for example, as a surface for killing and/or inhibiting the growth of a microbe.

BACKGROUND

[0003] Antimicrobial plastics are a growing market due, for example, to consumer concerns with health and safety. They may be useful, for example, in combatting the transmission of infectious diseases, the degradation of materials by microorganisms, and/or the formation of odor and discoloration. In automotive interiors, the dominant bacteria present are from the genus Staphylococcus , where 22.6% of the bacterial population are resistant to the antibiotic methicillin.¹

[0004] A fundamental technology shift in antimicrobial materials is underway in which a number of successful agents developed from the 1950s to 1970s utilizing organic and organometallic additives such as triclosan (5- chloro-2-(2,4-dichlorophenoxy)phenol) and 10, 10'-oxybisphenoxyarsine are now banned or under review by regulators in the European Union, the United States Food and Drug Administration and Health Canada due to their harmful effects towards human health and the environment. Inorganic compounds including silver ions have found applications in numerous products due to their efficacy against a wide range of bacteria. The advent of nanotechnology to produce particles less than 100 nm in size has led to a dramatic increase in potency for antimicrobial materials, a result of greater surface area to interact with microbes. However, there are major drawbacks for silver nanoparticles related to their high price and the concern of long term health and environmental risks with bioaccumulation.

[0005] Despite the wide range of available antimicrobial agents used, most antimicrobial surfaces are actually only a thin layer of an antimicrobial agent on a given substrate, which may lose its efficacy, for example, as the coatings wear off with physical weathering. Useful antimicrobial activity generally requires physical contact between the agent and the microorganism. Accordingly, a problem in producing true antimicrobial plastics is that many antimicrobial additives lose their activity once embedded in plastics, due to this reason. Additionally, currently available commercial antimicrobial agents may also have a high cost.

[0006] As the second most abundant natural polymer after cellulose, lignin is generally more economically competitive and eco-friendly than existing organic and organometallic antimicrobial agents. Phenolic lignin fragments have been disclosed to have antimicrobial properties. For example, Zemak and co-workers² tested different lignin fragments against a variety of microbes including E. coli , S. cerevisae, C. albicans , B. licheniformis , M. luteus and A. niger (filamentous fungi). Two particular fragments, isoeugenol and 2-(4- hydroxy-3-methylphenyl)-7-methoxy-3-methyl-5-propyl-coumaran (dehydro- diisoeugenol) exhibited enhanced antimicrobial activity. The incorporation of lignin into polymeric matrices has been investigated as a means to introduce low cost bio-based content to plastics, imparting improved physicochemical properties to the native polymer.³

[0007] However, lignin does not exhibit broad-spectrum antimicrobial activity. For example, Gram negative bacteria, such as E. coli and S. enteriditis, are not affected by caustic-extracted lignins⁴. Very little has been reported for the antimicrobial activity of lignin in plastics. Lignin-gelatin⁵ showed no antimicrobial activity over a broad spectrum of 26 bacteria, yeast and molds. Antimicrobial activity for Escherichia coli and Staphylococcus aureus was reported by Gregorov and co-workers⁶ for 2 wt% nano-Bjorkman lignin in polyethylene but the material was prepared via a solvent process, which is not cost-effective for industrial applications. [0008] Ma et al.⁷ have prepared a membrane with antifouling and antibacterial abilities from trimethyl quaternary ammonium salt grafted lignin (QAL) and polystyrene (PS). QAL was prepared by grafting varying degrees of trimethyl quaternary ammonium ion monomer (prepared from the reaction of trimethylamine and epichlorohydrin) onto alkali lignin. The membranes were prepared from a solvent process comprising adding a solution of PS dissolved in dichloromethane to a solution of QAL dissolved in dichloromethane to yield precipitates which were collected by filtration, washed with deionized water and then cast following the addition of 15% acetone. Cross-sections of the membranes were imaged by scanning electron microscopy (SEM) which showed increasing QAL content inside the membrane.

SUMMARY

[0009] Blends comprising quaternary ammonium-modified, lignin- containing materials dispersed in a polypropylene resin were prepared by a process comprising compounding the components in an extruder to form a plastic compound and injection molding of the resulting plastic compound. In contrast to comparable injection-molded blends made from polypropylene and unmodified Kraft lignin, a fine and homogenous dispersion of dimethyldioctadecylammonium (DMDOA)-modified Kraft lignin was present throughout the polymeric matrix and advantageously on the polypropylene polymer surface. The antimicrobial properties of exemplary modified lignin- polypropylene blends were found to be useful against both Gram-positive and Gram-negative bacteria. For example, a blend of polypropylene containing modified lignin tested according to ISO 22196:2007 (International Standard for Measurement of Antibacterial Activity on Plastics Surfaces) showed <67.03% and <89.23% reduction for E. coli and S. aureus , respectively, after 24 hours incubation.

[0010] Accordingly, the present application includes a process for preparing a plastic compound for use in forming an antimicrobial plastic blend, the process comprising:

compounding a plastic and a quaternary ammonium-modified, lignin-containing material to obtain the plastic compound. [0011] The present application also includes a process for preparing an antimicrobial plastic blend, the process comprising:

forming a plastic compound of the present application to obtain the antimicrobial plastic blend.

[0012] The present application further includes a process for preparing an antimicrobial plastic blend, the process comprising:

compounding a plastic and a quaternary ammonium-modified, lignin-containing material to obtain a plastic compound; and

forming the plastic compound to obtain the antimicrobial plastic blend.

[0013] The present application also includes an antimicrobial plastic blend comprising a quaternary ammonium-modified, lignin-containing material dispersed in a plastic. The present application further includes a use of an antimicrobial plastic blend of the present application as a surface for killing and/or inhibiting the growth of a microbe as well as a method of killing and/or inhibiting the growth of a microbe, the method comprising contacting the microbe with a surface of an antimicrobial plastic blend of the present application.

[0014] Other features and advantages of the present application will become apparent from the following detailed description. It should be understood, however, that the detailed description and the specific examples while indicating embodiments of the application are given by way of illustration only, since various changes and modifications within the spirit and scope of the application will become apparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The present application will now be described in greater detail with reference to the drawings in which:

[0016] Figure 1 shows exemplary scanning electron microscopy (SEM) images of an injection-molded blend of Indulin™ AT lignin and polypropylene according to a comparative example of the present application (upper image) and an injection-molded blend of a modified Indulin AT lignin dispersed in polypropylene according to an embodiment of the present application. Scale bars show 100 pm.

[0017] Figure 2 shows exemplary SEM images of a melt compounded blend of Protobind™ P1000 lignin and polypropylene according to a comparative example of the present application (upper left image) and melt compounded blends of Protobind™ lignin modified with varying amounts (10, 50 and 100% mol/mol PhOH) of dehydrogenated tallow)dimethylammonium cation according to embodiments of the present application (upper right image, lower left image and lower right image, respectively). Scale bars show 20 pm.

DETAILED DESCRIPTION

I. Definitions

[0018] Unless otherwise indicated, the definitions and embodiments described in this and other sections are intended to be applicable to all embodiments and aspects of the present application herein described for which they are suitable as would be understood by a person skilled in the art.

[0019] In understanding the scope of the present application, the term “comprising” and its derivatives, as used herein, are intended to be open ended terms that specify the presence of the stated features, elements, components, groups, integers, and/or steps, but do not exclude the presence of other unstated features, elements, components, groups, integers and/or steps. The foregoing also applies to words having similar meanings such as the terms, “including”, “having” and their derivatives. The term“consisting” and its derivatives, as used herein, are intended to be closed terms that specify the presence of the stated features, elements, components, groups, integers, and/or steps, but exclude the presence of other unstated features, elements, components, groups, integers and/or steps. The term“consisting essentially of”, as used herein, is intended to specify the presence of the stated features, elements, components, groups, integers, and/or steps as well as those that do not materially affect the basic and novel characteristic(s) of features, elements, components, groups, integers, and/or steps. [0020] Terms of degree such as “substantially”, “about” and “approximately” as used herein mean a reasonable amount of deviation of the modified term such that the end result is not significantly changed. These terms of degree should be construed as including a deviation of at least ±5% of the modified term if this deviation would not negate the meaning of the word it modifies.

[0021] The term“and/or” as used herein means that the listed items are present, or used, individually or in combination. In effect, this term means that “at least one of” or“one or more” of the listed items is used or present.

[0022] As used in this application, the singular forms“a”,“an” and“the” include plural references unless the content clearly dictates otherwise.

[0023] The term“alkyl” as used herein, whether it is used alone or as part of another group, means linear or branched chain, saturated alkyl groups. The number of carbon atoms that are possible in the referenced alkyl group are indicated by the numerical prefix“CniV. For example, the term Ci-4alkyl means an alkyl group having 1 , 2, 3 or 4 carbon atoms.

[0024] The term“alkenyl” as used herein, whether it is used alone or as part of another group, means linear or branched chain, unsaturated alkenyl groups. The number of carbon atoms that are possible in the referenced alkyl group are indicated by the numerical prefix“CniV. For example, the term C2- 30 alkenyl means an alkenyl group having 2, 3, 4, 5, 6, 7, 8, 9, 10, 1 1 , 12, 13, 14, 15, 16, 17, 18, 19, 20, 21 , 22, 23, 24, 25, 26, 27, 28, 29 or 30 carbon atoms and at least one double bond, for example 1 to 3, 1 to 2 or one double bond.

[0025] The term“suitable” as used herein means that the selection of specific reagents or conditions will depend on the reaction being performed and the desired results, but none-the-less, can generally be made by a person skilled in the art once all relevant information is known.

[0026] The expression“proceed to a sufficient extent” as used herein with reference to the reactions or process steps disclosed herein means that the reactions or process steps proceed to an extent that conversion of the starting material or substrate to product is maximized. Conversion may be maximized when greater than about 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95 or 100% of the starting material or substrate is converted to product.

[0027] The term “lignin” as used herein refers to a class of branched phenolic polymers that can bond or embed with other biopolymers (typically cellulose and/or hemicellulose) in plant cell walls. The composition of lignin can vary depending on the biological species but typically is a copolymer derived from varying ratios of the phenyl-propanoid units p-coumaryl alcohol, coniferyl alcohol and sinapyl alcohol often referred to as monolignols.

[0028] The term “p-coumaryl alcohol” as used herein refers to a compound having the following structure:

[0029] The term“coniferyl alcohol” as used herein refers to a compound having the following structure:

[0030] The term“sinapyl alcohol” as used herein refers to a compound having the following structure:

[0031] The term“phenolic group” as used herein in reference to a lignin refers to a group comprising a hydroxyl group bound to a phenyl ring in the lignin; i.e. it includes p-hydroxyphenyl, guaiacyl and syringyl groups.

[0032] The term“lignin-containing material” as used herein refers to any material comprising lignin and includes lignin as well as lignocellulose. [0033] The term “quaternary ammonium-modified” as used herein in reference to a lignin-containing material means that quaternary ammonium cations are ionically bonded to phenolate anions in the lignin-containing material, the phenolate anions being the conjugate bases of phenolic groups in the lignin.

II . Processes

[0034] Modified lignins can be compounded usefully with plastics such as polyolefins, polyesters, styrene-containing polymers or polyvinyls by extrusion at up to about 15-40% (w/w) with useful mechanical characteristics. For example, polymer blends comprising quaternary ammonium-modified, lignin-containing materials dispersed in a polypropylene polymer resin were prepared by a process comprising compounding the components in an extruder to form a plastic compound and injection molding of the resulting plastic compound. In contrast to comparable injection-molded plastic blends made from polypropylene and unmodified Kraft lignin, a fine and homogenous dispersion of DMDOA-modified Kraft lignin was present throughout the polymeric matrix and advantageously on the polypropylene polymer surface.

[0035] Accordingly, the present application includes a process for preparing a plastic compound for use in forming an antimicrobial plastic blend, the process comprising:

compounding a plastic and a quaternary ammonium-modified, lignin-containing material to obtain the plastic compound.

[0036] The lignin-containing material can be any suitable lignin-containing material. In an embodiment, the lignin-containing material is lignin, lignocellulose or combinations thereof. In another embodiment, the lignin-containing material is lignin. The lignin can be any suitable lignin. In an embodiment, the lignin is selected from Kraft lignin, soda lignin, organosolv lignin, a lignin obtained from a biorefinery process and combinations thereof. In another embodiment, the lignin is Kraft lignin. In a further embodiment, the lignin is soda lignin. The source of the lignin can be any suitable source. In an embodiment, the lignin is softwood lignin, hardwood lignin, a lignin from an agricultural source (e.g. wheat straw) or combinations thereof. In another embodiment, the lignin is softwood lignin or a wheat straw lignin. In another embodiment, the lignin is softwood lignin. In a further embodiment, the lignin is hardwood lignin. In another embodiment, the lignin is softwood Kraft lignin, hardwood Kraft lignin or combinations thereof. In a further embodiment, the lignin is softwood Kraft lignin. In another embodiment, the lignin is hardwood Kraft lignin. In another embodiment of the present application, the lignin is a pine Kraft lignin. In another embodiment, the lignin is a wheat straw soda lignin.

[0037] The quaternary ammonium cation is any suitable quaternary ammonium cation or mixtures thereof. In an embodiment, the groups on the quaternary ammonium cation or mixtures thereof are selected from alkyl groups, alkenyl groups and combinations thereof. In another embodiment, the quaternary ammonium cation is one or more quaternary ammonium cations of Formula I:

R¹

R⁴— N— R² (I)

R³ wherein R¹ , R², R³ and R⁴ are each independently selected from Ci-3oalkyl and C2-3oalkenyl. In an embodiment, R¹, R², R³ and R⁴ are each independently selected from Ci-3oalkyl. In another embodiment, two or three of R¹, R², R³ and R⁴ are each independently selected from Ci-4alkyl and the remaining one or two of R¹, R², R³ and R⁴ are each independently selected from Cio-3oalkyl or Cio- 3oalkenyl. In another embodiment, two or three of R¹, R², R³ and R⁴ are each independently selected from Ci-4alkyl and the remaining one or two of R¹ , R², R³ and R⁴ are each independently selected from Cio-3oalkyl. In another embodiment, two or three of R¹, R², R³ and R⁴ are each independently selected from Ci-4alkyl and the remaining one or two of R¹, R², R³ and R⁴ are each independently selected from Ci2-24alkyl, optionally linear Ci2-24alkyl. In a further embodiment, two or three of R¹, R², R³ and R⁴ are each independently selected from Ci-4alkyl and the remaining one or two of R¹, R², R³ and R⁴ are each independently selected from Ci4-2oalkyl, optionally linear Ci4-2oalkyl. In an embodiment, the Ci-4alkyl is methyl.

[0038] In an embodiment, R¹ and R² are each independently selected from Ci-4alkyl and R³ and R⁴ are each independently selected from Cio-3oalkyl. In another embodiment, R¹ and R² are each independently selected from Ci- 4alkyl and R³ and R⁴ are each independently selected from Ci2-24alkyl, optionally linear Ci2-24alkyl. In a further embodiment, R¹ and R² are each independently selected from Ci-4alkyl and R³ and R⁴ are each independently selected from Ci4-2oalkyl, optionally linear Ci4-2oalkyl. In another embodiment of the present application, R¹ and R² are each independently selected from Ci- 4alkyl and R³ and R⁴ are each n-octadecyl. In an embodiment, the Ci-4alkyl is methyl. In a further embodiment, R¹ and R² are each methyl and R³ and R⁴ are each n-octadecyl; i.e. the alkyl quaternary ammonium cation of Formula I is DMDOA cation.

[0039] In an embodiment, R¹ , R² and R³ are each independently selected from Ci-4alkyl and R⁴ is Cio-3oalkyl. In another embodiment, R¹ , R² and R³ are each independently selected from Ci-4alkyl and R⁴ is Ci2-24alkyl, optionally linear Ci2-24alkyl. In a further embodiment, R¹ , R² and R³ are each independently selected from Ci-4alkyl and R⁴ is Ci4-2oalkyl, optionally linear Ci4- 2oalkyl. In a further embodiment, R¹ , R² and R³ are each independently selected from Ci-4alkyl and R⁴ is n-hexadecyl. In an embodiment, the Ci-4alkyl is methyl. In a further embodiment, R¹ , R² and R³ are each methyl and R⁴ is n-hexadecyl; i.e. the alkyl quaternary ammonium cation of Formula I is cetyltrimethylammonium cation.

[0040] In an embodiment, the quaternary ammonium is a mixture of quaternary ammonium cations of Formula I, wherein each R¹ and R² are independently selected from Ci-4alkyl and each R³ and R⁴ are independently selected from Cio-3oalkyl and Cio-3oalkenyl. In another embodiment, the quaternary ammonium is a mixture of quaternary ammonium cations of Formula

I, wherein each R¹ and R² are independently selected from Ci-4alkyl and each R³ and R⁴ are independently selected from Ci2-24alkyl and Ci2-24alkenyl, optionally linear Ci2-24alkyl or Ci2-24alkenyl. In a further embodiment, the quaternary ammonium is a mixture of quaternary ammonium cations of Formula I, wherein each R¹ and R² are independently selected from Ci-4alkyl and each R³ and R⁴ are independently selected from Ci2-2oalkyl, optionally linear Ci2-2oalkyl. In another embodiment of the present application, the quaternary ammonium is a mixture of quaternary ammonium cations of Formula I, wherein each R¹ and R² are independently selected from Ci-4alkyl and each R³ and R⁴ are selected from linear Ci2-2oalkyl, wherein the alkyl chain length distribution is: no more than 2% Ci2, from 1-5% Ci4, from 25-35% Ci6, from 60-70% Cie and no more than 2% C20. In an embodiment, the Ci-4alkyl is methyl. In a further embodiment, R¹ and R² are each methyl and R³ and R⁴ are linear Ci2-2oalkyl, wherein the alkyl chain length distribution is: no more than 2% C12, from 1-5% C14, from 25-35% C16, from 60-70% Cie and no more than 2% C20.; i.e. the mixture of alkyl quaternary ammonium cations of Formula I is a dehydrogenated tallow)dimethylammonium cation. Suitable sources of dehydrogenated tallow)dimethylammonium cation are commercially available. For example, di(hydrogenated tallow)dimethylammonium chloride (CAS No. 61789-80-8) is available from commercial sources. The bromide form of the onium ion may also be available commercially. Alternatively, suitable sources of di(hydrogenated tallow)dimethylammonium cation can be obtained by reacting tallow fatty acids with NH3 and dehydrating to obtain an intermediate fatty acid nitrile which is then reduced to obtain a secondary amine, methylated with formaldehyde and quaternized with a suitable methyl halide such as methylchloride (see, for example: European Centre for Ecotoxicology and Toxicology of Chemicals (ECETOC), Technical Report No. 53, DHTDMAC:- Aquatic and Terrestrial Hazard Assessment CAS No. 61789-80-8, February 1993, ISSN-0773-8072- 53).

[0041] In an embodiment, the molar ratio between phenolic groups in the lignin-containing material and the quaternary ammonium cation is from about 1 : 1 to about 1 : 0.05. In another embodiment, the molar ratio between phenolic groups in the lignin-containing material and the quaternary ammonium cation is from about 1 : 1 to about 1 : 0.1 . In another embodiment of the present application, the molar ratio between phenolic groups in the lignin-containing material and the quaternary ammonium cation is about 1 : 1 to about 1 : 0.25. In a further embodiment, the molar ratio between phenolic groups in the lignin- containing material and the quaternary ammonium cation is from about 1 : 0.5 to about 1 : 0.25. In another embodiment, the molar ratio between phenolic groups in the lignin-containing material and the quaternary ammonium cation is from about 1 : 0.2 to about 1 : 0.3. In another embodiment, the molar ratio between phenolic groups in the lignin-containing material and the quaternary ammonium cation is about 1 : 0.25.

[0042] The plastic is any suitable plastic. For example, suitable plastics may be obtained from petroleum-based and/or renewable resources. In an embodiment, the plastic is a thermoplastic, a thermoset, an elastomer or combinations thereof. In another embodiment, the plastic is a thermoplastic. In a further embodiment, the plastic is a thermoset. In another embodiment of the present application, the plastic is an elastomer. In another embodiment, the plastic comprises, consists essentially of or consists of a polypropylene, a propylene copolymer, a polyethylene, an ethylene copolymer, polybutylene succinate, a styrene-containing polymer, a polyvinyl or a polylactide resin. In a further embodiment, the plastic comprises, consists essentially of or consists of a polypropylene.

[0043] In an embodiment, the quaternary ammonium-modified, lignin- containing material is prepared by a process comprising reacting an alkaline aqueous solution comprising the lignin-containing material with an aqueous solution comprising the quaternary ammonium cation for a time and at a temperature for the conversion of the lignin-containing material and the quaternary ammonium cation to the quaternary ammonium-modified, lignin- containing material to proceed to a sufficient extent. It will be appreciated by the person skilled in the art that the quaternary ammonium cation in the aqueous solution comprising the quaternary ammonium cation is in the form of a suitable salt such as a chloride or bromide salt. In an embodiment, the alkaline aqueous solution comprising the lignin-containing material has a lignin concentration of from about 2% (w/v) to about 40% (w/v), about 15% (w/v) to about 40% (w/v), about 15% (w/v) to about 25% (w/v), about 20% (w/v) or about 15% (w/v). It will be appreciated by the person skilled in the art that the amount of base (e.g. NaOH) dissolved in water is chosen in light of the desired stoichiometric ratio between the hydroxide ion of the base and the phenolic groups of the lignin in the lignin-containing material and is typically from about 10% to about 100%. In an embodiment, the molar ratio between the NaOH : phenolic groups in the lignin-containing material : the quaternary ammonium cation is from about 0.20 : 1 : 0.20 to about 0.30 : 1 : 0.30 or about 0.25 : 1 : 0.25.

[0044] In another embodiment, the aqueous solution comprising the quaternary ammonium cation has a concentration of about 0.01 M to about 0.25 M, about 0.08 M or about 0.14 M. In an embodiment, the lignin-containing material and the quaternary ammonium cation are reacted for a time of at least about 5 minutes at a temperature of about 10°C to about 100°C or about 50°C to about 60°C.

[0045] The means for compounding is any suitable means. In an embodiment, the compounding comprises extruding the molten plastic comprising the quaternary ammonium-modified, lignin-containing material and optionally the additives, if present. In another embodiment, the compounding comprises mixing the plastic, the quaternary ammonium-modified, lignin- containing material and optionally the additive(s), if present, in the molten stage of the plastic in a twin-screw extruder and optionally further comprises extruding the molten plastic comprising the quaternary ammonium-modified, lignin- containing material and optionally the additive(s), if present as an extrudate. The conditions for compounding may depend, for example, on the identity of the plastic. In an embodiment, the plastic is a polypropylene resin (for example, a polypropylene resin having a melt flow index of about 12 g/ 10 min such as polypropylene Pro-fax 6323) and the conditions comprise a temperature of from about 170°C to about 220°C or about 180°C, and a screw speed of from about 50 rpm to about 300 rpm or about 100 rpm.

[0046] In embodiments wherein the plastic compound is extruded, the process may further comprise cooling the extrudate and forming the extrudate into pellets. The means for cooling and/or forming extrudate into pellets can be any suitable means, the selection of which can be made by the person skilled in the art.

[0047] The present application also includes a use of a plastic blend of the present application in forming an antimicrobial plastic blend. Accordingly, the present application further includes a process for preparing an antimicrobial plastic blend, the process comprising:

[0048] In some embodiments, the plastic compound of the present application is obtained from a process for preparing a plastic compound for use in forming an antimicrobial plastic blend of the present application. Accordingly, the present application further includes a process for preparing an antimicrobial plastic blend, the process comprising:

forming the plastic compound to obtain the antimicrobial plastic blend.

[0049] The means for forming is any suitable means. In an embodiment, the forming comprises injection molding, extrusion, blowing, casting, calendaring, thermoforming or compression. In another embodiment, the forming comprises injection molding. The conditions for forming (e.g. injection molding, extrusion, blowing, casting, calendaring, thermoforming or compression) may depend, for example, on the identity of the plastic and can be readily selected by a person skilled in the art. In an embodiment, the plastic is a polypropylene resin (for example, a polypropylene resin having a melt flow index of about 12 g/ 10 min such as polypropylene Pro-fax 6323) and the conditions comprise injection molding at a temperature of from about 170°C to about 220°C or about 180°C.

[0050] In an embodiment, the antimicrobial plastic blend or plastic compound comprises from about 1 % (w/w) to about 50% (w/w) of the quaternary ammonium-modified, lignin-containing material, based on the total weight of the antimicrobial plastic blend or plastic compound, as the case may be. In another embodiment, the antimicrobial plastic blend or plastic compound comprises from about 5% (w/w) to about 30% (w/w) of the quaternary ammonium-modified, lignin-containing material, based on the total weight of the antimicrobial plastic blend or plastic compound, as the case may be. In a further embodiment of the present application, the antimicrobial plastic blend or plastic compound comprises from about 10% (w/w) to about 20% (w/w) of the quaternary ammonium-modified, lignin-containing material, based on the total weight of the antimicrobial plastic blend or plastic compound, as the case may be. In another embodiment, the antimicrobial plastic blend or plastic compound comprises from about 15% (w/w) to about 25% (w/w) of the quaternary ammonium-modified, lignin-containing material, based on the total weight of the antimicrobial plastic blend or plastic compound, as the case may be.

[0051] In some embodiments, the antimicrobial plastic blend or plastic compound further comprises one or more additives such as but not limited to a compatibilizer, a filler, a processing aid, a flame retardant, a reinforcement, an impact modifier or combinations thereof. The person skilled in the art would be able to select suitable conditions for compounding such additives with the plastic and the quaternary ammonium-modified, lignin-containing material to obtain the antimicrobial plastic blend or plastic compound, as the case may be, comprising such additives. The term“compatibilizer” as used herein refers to an additive that when added to a blend of immiscible materials during extrusion, modifies the interfacial properties of the materials and stabilizes the melt blend. The compatibilizer, when present, can be any suitable compatibilizer. In an embodiment, the compatibilizer comprises, consists essentially of or consists of a suitable maleic hydride grafted polypropylene, acrylic acid grafted polypropylene, maleic hydride grafted polyethylene, acrylic acid grafted polyethylene, maleic hydride grafted propylene copolymer, acrylic acid grafted propylene copolymer, maleic hydride grafted ethylene copolymer, acrylic acid grafted ethylene copolymer or combinations thereof. In another embodiment, the compatibilizer comprises, consists essentially of or consists of a maleic hydride grafted polypropylene. In other embodiments of the present application, the antimicrobial plastic blend or the plastic compound, as the case may be, consists of or consists essentially of the plastic and the quaternary ammonium-modified, lignin-containing material.

III. Plastic Compounds, Blends and Uses

[0052] The antimicrobial properties of exemplary DMDOA-modified lignin- polypropylene blends were found to be useful against both Gram-positive and Gram-negative bacteria. For example, a blend of polypropylene containing modified lignin tested according to ISO 22196:2007 (International Standard for Measurement of Antibacterial Activity on Plastics Surfaces) showed <67.03% and <89.23% reduction for E. coli and S. aureus , respectively, after 24 hours incubation.

[0053] Accordingly, the present application also includes an antimicrobial plastic blend comprising a quaternary ammonium-modified, lignin- containing material dispersed in a plastic. In some embodiments, the antimicrobial plastic blend is prepared according to a process for preparing an antimicrobial plastic blend of the present application. The present application also includes a plastic compound for use in forming an antimicrobial plastic blend, the plastic compound comprising a plastic and a quaternary ammonium- modified, lignin-containing material. In some embodiments, the plastic compound is prepared according to a process for preparing a plastic compound for use in forming an antimicrobial plastic blend of the present application.

[0054] The lignin-containing material can be any suitable lignin-containing material. In an embodiment, the lignin-containing material is lignin, lignocellulose or combinations thereof. In another embodiment, the lignin-containing material is lignin. The lignin can be any suitable lignin. In an embodiment, the lignin is selected from Kraft lignin, soda lignin, organosolv lignin, a lignin obtained from a biorefinery process and combinations thereof. In another embodiment, the lignin is Kraft lignin. In a further embodiment, the lignin is soda lignin. The source of the lignin can be any suitable source. In an embodiment, the lignin is softwood lignin, hardwood lignin, a lignin from an agricultural source (e.g. wheat straw) or combinations thereof. In another embodiment, the lignin is softwood lignin or a wheat straw lignin. In another embodiment, the lignin is softwood lignin. In a further embodiment, the lignin is hardwood lignin. In another embodiment, the lignin is softwood Kraft lignin, hardwood Kraft lignin or combinations thereof. In a further embodiment, the lignin is softwood Kraft lignin. In another embodiment, the lignin is hardwood Kraft lignin. In another embodiment of the present application, the lignin is a pine Kraft lignin. In another embodiment, the lignin is a wheat straw soda lignin.

[0055] The quaternary ammonium cation is any suitable quaternary ammonium cation or mixtures thereof. In an embodiment, the groups on the quaternary ammonium cation or mixtures thereof are selected from alkyl groups, alkenyl groups and combinations thereof. In another embodiment, the quaternary ammonium cation is one or more quaternary ammonium cations of Formula I:

R¹

R⁴— N— R² (I)

R³ wherein R¹ , R², R³ and R⁴ are each independently selected from Ci-3oalkyl and C2-3oalkenyl. In an embodiment, R¹, R², R³ and R⁴ are each independently selected from Ci-3oalkyl. In another embodiment, two or three of R¹, R², R³ and R⁴ are each independently selected from Ci-4alkyl and the remaining one or two of R¹, R², R³ and R⁴ are each independently selected from Cio-3oalkyl or C10- 3oalkenyl. In an embodiment, two or three of R¹, R², R³ and R⁴ are each independently selected from Ci-4alkyl and the remaining one or two of R¹ , R², R³ and R⁴ are each independently selected from Cio-3oalkyl. In another embodiment, two or three of R¹, R², R³ and R⁴ are each independently selected from Ci-4alkyl and the remaining one or two of R¹, R², R³ and R⁴ are each independently selected from Ci2-24alkyl, optionally linear Ci2-24alkyl. In a further embodiment, two or three of R¹, R², R³ and R⁴ are each independently selected from Ci-4alkyl and the remaining one or two of R¹, R², R³ and R⁴ are each independently selected from Ci4-2oalkyl, optionally linear Ci4-2oalkyl. In an embodiment, the Ci-4alkyl is methyl. [0056] In an embodiment, R¹ and R² are each independently selected from Ci-4alkyl and R³ and R⁴ are each independently selected from Cio-3oalkyl. In another embodiment, R¹ and R² are each independently selected from Ci- 4alkyl and R³ and R⁴ are each independently selected from Ci2-24alkyl, optionally linear Ci2-24alkyl. In a further embodiment, R¹ and R² are each independently selected from Ci-4alkyl and R³ and R⁴ are each independently selected from Ci4-2oalkyl, optionally linear Ci4-2oalkyl. In another embodiment of the present application, R¹ and R² are each independently selected from Ci- 4alkyl and R³ and R⁴ are each n-octadecyl. In an embodiment, the Ci-4alkyl is methyl. In a further embodiment, R¹ and R² are each methyl and R³ and R⁴ are each n-octadecyl; i.e. the alkyl quaternary ammonium cation of Formula I is DMDOA cation.

[0057] In an embodiment, R¹ , R² and R³ are each independently selected from Ci-4alkyl and R⁴ is Cio-3oalkyl. In another embodiment, R¹ , R² and R³ are each independently selected from Ci-4alkyl and R⁴ is Ci2-24alkyl, optionally linear Ci2-24alkyl. In a further embodiment, R¹ , R² and R³ are each independently selected from Ci-4alkyl and R⁴ is Ci4-2oalkyl, optionally linear Ci4- 2oalkyl. In a further embodiment, R¹ , R² and R³ are each independently selected from Ci-4alkyl and R⁴ is n-hexadecyl. In an embodiment, the Ci-4alkyl is methyl. In a further embodiment, R¹ , R² and R³ are each methyl and R⁴ is n-hexadecyl; i.e. the alkyl quaternary ammonium cation of Formula I is cetyltrimethylammonium cation.

[0058] In an embodiment, the quaternary ammonium is a mixture of quaternary ammonium cations of Formula I, wherein each R¹ and R² are independently selected from Ci-4alkyl and each R³ and R⁴ are independently selected from Cio-3oalkyl and Cio-3oalkenyl. In another embodiment, the quaternary ammonium is a mixture of quaternary ammonium cations of Formula I, wherein each R¹ and R² are independently selected from Ci-4alkyl and each R³ and R⁴ are independently selected from Ci2-24alkyl and Ci2-24alkenyl, optionally linear Ci2-24alkyl or Ci2-24alkenyl. In a further embodiment, the quaternary ammonium is a mixture of quaternary ammonium cations of Formula I, wherein each R¹ and R² are independently selected from Ci-4alkyl and each R³ and R⁴ are independently selected from Ci2-2oalkyl, optionally linear C12- 2oalkyl. In another embodiment of the present application, the quaternary ammonium is a mixture of quaternary ammonium cations of Formula I, wherein each R¹ and R² are independently selected from Ci-4alkyl and each R³ and R⁴ are selected from linear Ci2-2oalkyl, wherein the alkyl chain length distribution is: no more than 2% C12, from 1 -5% C14, from 25-35% C16, from 60-70% C18 and no more than 2% C20. In an embodiment, the Ci-4alkyl is methyl. In a further embodiment, R¹ and R² are each methyl and R³ and R⁴ are linear Ci2-2oalkyl, wherein the alkyl chain length distribution is: no more than 2% C12, from 1-5% Ci 4, from 25-35% C16, from 60-70% C18 and no more than 2% C20.; i.e. the mixture of alkyl quaternary ammonium cations of Formula I is a dehydrogenated tallow)dimethylammonium cation.

[0059] In an embodiment, the molar ratio between phenolic groups in the lignin-containing material and the quaternary ammonium cation is from about 1 : 1 to about 1 : 0.05. In another embodiment, the molar ratio between phenolic groups in the lignin-containing material and the quaternary ammonium cation is from about 1 : 1 to about 1 : 0.1 . In another embodiment of the present application, the molar ratio between phenolic groups in the lignin-containing material and the quaternary ammonium cation is about 1 : 1 to about 1 : 0.25. In a further embodiment, the molar ratio between phenolic groups in the lignin- containing material and the quaternary ammonium cation is from about 1 : 0.5 to about 1 : 0.25. In another embodiment, the molar ratio between phenolic groups in the lignin-containing material and the quaternary ammonium cation is from about 1 : 0.2 to about 1 : 0.3. In another embodiment, the molar ratio between phenolic groups in the lignin-containing material and the quaternary ammonium cation is about 1 : 0.25.

[0060] The plastic is any suitable plastic. For example, suitable plastics may be obtained from petroleum-based and/or renewable resources. In an embodiment, the plastic is a thermoplastic, a thermoset, an elastomer or combinations thereof. In another embodiment, the plastic is a thermoplastic. In a further embodiment, the plastic is a thermoset. In another embodiment of the present application, the plastic is an elastomer. In another embodiment, the plastic comprises, consists essentially of or consists of a polypropylene, a propylene copolymer, a polyethylene, an ethylene copolymer, polybutylene succinate, a styrene-containing polymer, a polyvinyl or a polylactide resin. In a further embodiment, the plastic comprises, consists essentially of or consists of a polypropylene.

[0061] In an embodiment, the antimicrobial plastic blend or plastic compound comprises from about 1 % (w/w) to about 50% (w/w) of the quaternary ammonium-modified, lignin-containing material, based on the total weight of the antimicrobial plastic blend or plastic compound, as the case may be. In another embodiment, the antimicrobial plastic blend or plastic compound comprises from about 5% (w/w) to about 30% (w/w) of the quaternary ammonium-modified, lignin-containing material, based on the total weight of the antimicrobial plastic blend or plastic compound, as the case may be. In a further embodiment of the present application, the antimicrobial plastic blend or plastic compound comprises from about 10% (w/w) to about 20% (w/w) of the quaternary ammonium-modified, lignin-containing material, based on the total weight of the antimicrobial plastic blend or plastic compound, as the case may be. In another embodiment, the antimicrobial plastic blend or plastic compound comprises from about 15% (w/w) to about 25% (w/w) of the quaternary ammonium-modified, lignin-containing material, based on the total weight of the antimicrobial plastic blend or plastic compound, as the case may be.

[0062] In some embodiments, the antimicrobial plastic blend or plastic compound further comprises one or more additives such as but not limited to a compatibilizer, a filler, a processing aid, a flame retardant, a reinforcement, an impact modifier or combinations thereof. The compatibilizer, when present, can be any suitable compatibilizer. In an embodiment, the compatibilizer comprises, consists essentially of or consists of a suitable maleic hydride grafted polypropylene, acrylic acid grafted polypropylene, maleic hydride grafted polyethylene, acrylic acid grafted polyethylene, maleic hydride grafted propylene copolymer, acrylic acid grafted propylene copolymer, maleic hydride grafted ethylene copolymer, acrylic acid grafted ethylene copolymer or combinations thereof. In another embodiment, the compatibilizer comprises, consists essentially of or consists of a maleic hydride grafted polypropylene. In other embodiments of the present application, the antimicrobial plastic blend or plastic compound consists of or consists essentially of the plastic and the quaternary ammonium- modified, lignin-containing material.

[0063] In an embodiment, the quaternary ammonium-modified, lignin- containing material is homogeneously dispersed throughout the plastic and on the surface of the antimicrobial plastic blend.

[0064] In an embodiment, the antimicrobial plastic blend is an antibacterial plastic blend (i.e. kills and/or inhibits the growth of bacteria), an antifungal plastic blend (i.e. kills and/or inhibits the growth of fungi) or a combination thereof. In another embodiment, the antimicrobial plastic is an antibacterial plastic blend. In a further embodiment, the antimicrobial plastic blend has antibacterial activity against Gram-negative bacteria, Gram-positive bacteria or a combination thereof. In a further embodiment, the antimicrobial plastic blend has antibacterial activity against Gram-negative bacteria and Gram-positive bacteria. In another embodiment, the Gram-negative bacteria is Escherichia coli. In a further embodiment, the Gram-positive bacteria is Staphylococcus aureus. In another embodiment, the Gram-negative bacteria is Escherichia coli and the Gram-positive bacteria is Staphylococcus aureus.

[0065] The present application also includes a use of the antimicrobial plastic blend of the present application for killing and/or inhibiting the growth of a microbe. In an embodiment, the microbe is bacteria, fungi or a combination thereof. In another embodiment, the microbe is bacteria. In a further embodiment, the bacteria are Gram-negative, Gram-positive or combinations thereof. In a further embodiment, the bacteria are Gram-negative. In another embodiment, the bacteria are Gram-positive. In a further embodiment, the bacteria are a combination of Gram-negative bacteria and Gram-positive bacteria. In another embodiment of the present application, the Gram-negative bacteria is Escherichia coli. In a further embodiment, the Gram-positive bacteria is Staphylococcus aureus. In another embodiment, the Gram-negative bacteria is Escherichia coli and the Gram-positive bacteria is Staphylococcus aureus. [0066] The present application also includes a method of killing and/or inhibiting the growth of a microbe, the method comprising contacting the microbe with a surface of an antimicrobial plastic blend of the present application. In an embodiment, the microbe is bacteria, fungi or a combination thereof. In another embodiment, the microbe is bacteria. In a further embodiment, the bacteria are Gram-negative, Gram-positive or combinations thereof. In a further embodiment, the bacteria are Gram-negative. In another embodiment, the bacteria are Gram-positive. In a further embodiment, the bacteria are a combination of Gram-negative bacteria and Gram-positive bacteria. In another embodiment of the present application, the Gram-negative bacteria is Escherichia coli. In a further embodiment, the Gram-positive bacteria is Staphylococcus aureus. In another embodiment, the Gram-negative bacteria is Escherichia coli and the Gram-positive bacteria is Staphylococcus aureus.

[0067] Such methods and uses may have applications in fields such as but not limited to transportation, household products, food, healthcare, agriculture, and/or construction, where controlling microbes such as bacteria is desirable.

[0068] The following non-limiting examples are illustrative of the present application:

EXAMPLES

Example 1 : Grafting of lignin with alkyl quaternary ammonia cations

I. General Preparation of Modified Lignins

[0069] Materials: The Indulin AT® softwood Kraft lignin (KL) used in this study was supplied by MeadWestvaco Co., Charleston, SC, USA. Dimethyldioctadecylammonium bromide (DMDOAB, >98% pure) was obtained from TCI Chemicals. Cetyltrimethylammonium bromide (CTMAB, 99% pure), tetramethylammonium chloride (TMAC, >98% pure), sodium hydroxide (NaOH, >98% pure), acetic acid (>99.7% pure) and hydrochloric acid (37% pure) were purchased from Sigma-Aldrich and were used as received. Polypropylene Pro fax 6323 (homopolymer, melt flow index = 12 g/10 min) was obtained from LyondellBasell Industries. Maleic anhydride modified polypropylene sample (MAPP) named Epolene™ E-43 (acid number 16, M_w 16,000) was purchased from Eastman Chemicals and was used as a coupling agent (compatibilizer).

[0070] Preparation of alkaline Kraft lignin (AKL): Alkaline solutions (0.2 mol/L, pH about 12.90) were prepared by adding in a 1000 ml_ beaker, 8 g of NaOH in 1000 ml_ of deionized water. The pH of the alkaline solutions was measured using a pH-meter. The amount of NaOH dissolved in water was chosen to respect the stoichiometric ratio between NaOH and the phenolic group of lignin (about 2 mmol/g). Kraft lignin solutions (KL10%) (100 g/L) were then prepared by dissolving in a 250 ml_ beaker, 10 g of the Kraft lignin in 100 ml_ of the prepared alkaline solution. The dissolution of the Kraft lignin in the alkaline solution was performed while stirring at 350 rpm at 60°C for 30 minutes.

[0071] Preparation of ionic solution: Ionic solutions (50 g/L) were prepared by adding a known mass of each alkyl quaternary ammonium salt (onium ion) in a 500 mL beaker containing a known volume of deionized water. The solution was mechanically stirred progressively from 1300 to 1700 rpm at 60°C for 30 minutes. The pH of the solution was measured using a pH meter.

[0072] Complex formation: The reaction was carried out by mixing the alkaline Kraft lignin solution and the ionic solution together, while stirring from 1700 to 700 rpm (as viscosity decreased while introducing the AKL) at 60°C for a minimum of 20 minutes before any further manipulation.

[0073] For the first set of experiments, five different phenolic group of lignin to onium ion molar ratios were used (1 :1 , 1 :0.75, 1 :0.5, 1 :0.25 and 1 :0.10) while keeping the stoichiometric ratio between phenolic group of lignin and NaOH.

[0074] For the second set of experiments, the onium ion to NaOH molar ratio was the parameter varied (0.75:0.75, 0.5:0.5 and 0.25:0.25 for 1 mole phenolic of lignin).

[0075] Precipitation may take place as the result of the ionic exchange reaction. The pH of the mixture at the end of the reaction was measured.

[0076] The precipitated complexes were separated from the supernatant solution by centrifugation at 4700 rpm for 30 minutes. The precipitate was first washed with alkaline solution then centrifuged at 4700 rpm for 30 minutes to remove unreacted lignin. The supernatant from the second centrifugation was added to the one obtained from the first centrifugation. The precipitate was then rinsed with warm deionized water (50°C) and then centrifuged at 4700 rpm for 20 minutes 3 times. The precipitate was dried to constant mass at 60°C for 48 hours. The precipitate was then weighed and the yield of the complex formation was measured. Samples were ground for further tests.

[0077] Hydrochloric acid (1 mol/L) was then added to the supernatant to bring down the pH to about 3 in order to precipitate the unreacted lignin. The suspension was centrifuged at 4700 rpm for 20 minutes to separate the unreacted lignin from the suspension. The amount of unreacted Kraft lignin was evaluated based on the mass obtained after drying the sample in the oven at 60°C for 48 hours.

II. General Procedure for Processing

[0078] Melt-compounding: Pre (dry blend) was prepared by dry mixing lignin and polypropylene (PP) in powder form. Eastman’s Epolene 43 (E-43), a maleic anhydride grafted PP, was used as a compatibilizer in 1 case. The pre (dry-blend) was fed into a LabTech twin-screw extruder with the configuration and parameters as follows: T emperature: 180°C in all zones, Screw speed: 100 rpm, Output: 2 kg/h. The blends can also be prepared by feeding directly the lignin and the PP into the extruder at the beginning of the extruder. Alternatively, the lignin can also be fed into the extruder by side feeding.

[0079] Injection molding: The blends at ratios indicated hereinbelow were injected in an injection-molding machine (Boy machines Inc., USA) at 180°C in all zones. Dog-bones, bars and disks were obtained.

III. Results and Discussion

[0080] In the absence of compatibilizer the unmodified lignin was poorly dispersed in the polypropylene matrix but the modified lignins were finely dispersed in the matrix. While not wishing to be limited by theory, the fine lignin dispersion results in a higher surface area for the lignin to be in contact with the environment. This is one of the most important criteria that may maximize the antimicrobial efficacy. When the concentration of the oniums was reduced, the fineness of lignin dispersion decreased. For the case of DMDOAB when the ratio of onium ion was less than 0.25 mole per 1 mole phenolate (PhOH) poor lignin dispersion was observed.

[0081] Figure 1 shows a comparison between an unmodified Indulin AT- polypropylene blend and a DMDOA-modified Indulin AT-polypropylene blend (NaOH : PhOH : onium ion ratio of 0.25 : 1 : 0.25). As can be clearly seen in Figure 1 , the dispersion of the modified Indulin AT in polypropylene was excellent in contrast to the poor dispersion of the unmodified Indulin AT in polypropylene.

[0082] Table 1 provides an overview of the mechanical properties of various ratios of unmodified Indulin AT-polypropylene blends and a DMDOA- modified Indulin AT-polypropylene blend (NaOH : PhOH : onium ion ratio of 0.25 : 1 : 0.25). The results indicate that the blends comprising the modified lignin had superior tensile modulus as well as flexural strength and modulus and impact strength in comparison to the polypropylene matrix.

Example 2: Grafting of lignin with dehydrogenated tallow)dimethylammonium cations

I. Materials and Methods

[0083] The source of dehydrogenated tallow)dimethylammonium cations was Arquad™ 2HT-75 which is a dehydrogenated tallow)dimethylammonium chloride (CAS Number 61789-80-8) obtained from Sigma-Aldrich. The lignin was Protobind P1000, a wheat straw lignin extracted by the soda process.

[0084] The amount of Arquad 2HT-75 was 10, 50 and 100% mol/phenol- mol in lignin corresponding to sample names PB10, PB50 and PB100. The moles of NaOH were equivalent with the moles of Arquad 2HT-75.

[0085] To prepare the modified lignins, NaOH was first dissolved in water. The amount of water was about 6 times the volume of the lignin. The Arquad 2HT-75 was also dissolved in water to obtain a 2 wt% solution and this was heated to 60°C. The lignin was then dissolved into the NaOH solution at 50°C for 20 minutes. The lignin suspension/solution was then mixed into the Arquad 2HT-75 solution and maintained at 50°C for 30 minutes. The material obtained was washed several times with water and then dried in air then in an oven.

[0086] Melt compounding of 10 wt% modified lignins PB10, PB50 and PB100 as well as unmodified lignin in polypropylene PP1274 was carried out in a Haake™ minicompounder with a very minimum shear rate (only conveying elements) at 100 rpm at 190°C for 5 minutes.

II. Results and Discussion

[0087] Modified lignins PB10, PB50 and PB100 were soluble in toluene, swelled in hexane and were not soluble in water. Figure 2 shows SEM images comparing a melt compounded blend of unmodified Protobind™ P1000 lignin and polypropylene (upper left image) and melt compounded blends of modified lignins PB10 (upper right image), PB50 (lower left image) and PB100 (lower right image). As can be seen in Figure 2, an improvement in compatibility with PP was seen with all modified lignins over the unmodified lignin. As the fatty acid-based quaternary amine content increased, the finer the lignin dispersion in the PP.

Example 3: Antibacterial activity of modified lignin-polypropylene blends

I. Materials and Methods

[0088] Preparation of modified lignin: Modified lignin 1 (L1 ) and modified lignin 2 (L2) were prepared according to the general procedure described in Example 1 using the parameters summarized in Table 2.

[0089] Preparation of modified lignin-polypropylene blend: Melt compounding and injection molding were carried out according to the general procedure described in Example 1 using a ratio by weight of polypropylene to modified lignin of 5 : 1 to obtain the samples for antibacterial testing.

[0090] Evaluation of antimicrobial efficacy: Antimicrobial efficacy was evaluated in line with ISO 22196:2007, International Standard for Measurement of Antibacterial Activity on Plastics Surfaces. Test organisms were Escherichia coli ATCC 8739 and Staphylococcus aureus ATCC 6538. Each sample was inoculated with 0.4 ml_ of a 0.2% nutrient broth seeded with a standardized culture of the test organism. The inoculated sample was covered with an inert film and incubated at 36±2°C in a humidity chamber for 24 hours. Microbial counts of the samples were determined and the percent reduction of microorganisms (treated versus untreated sample at timepoint) and antibacterial activity were calculated.

II . Results and Discussion

[0091] Tables 3 and 4 show a summary of the results of the testing for the Gram-negative bacteria E. coli and Gram-positive bacteria S. aureus , respectively. Percent reduction and antibacterial activity were calculated against the untreated control at the corresponding time point. After 24 hours incubation in the ISO 22196 test method, the L1 -PP sample showed a <67.03% reduction and an antibacterial activity value of <0.48 for E. coli. The L2-PP sample showed a <84.49% reduction and an antibacterial activity value of <0.81 for E. coli. After 24 hours incubation in the ISO 22196 test method, the L2-PP sample showed no activity against the Gram-positive bacteria S. aureus. However, the L1 -PP sample showed an 89.23% reduction and an antibacterial activity value of 0.97. While not wishing to be limited by theory, as the characteristics of DMDHTA are very similar to DMODA it is believed that DMDHTA modified lignin-polypropylene blends will behave similar to DMODA modified lignin-polypropylene blends in terms of antibacterial activity.

[0092] While the present application has been described with reference to what are presently considered to be the preferred examples, it is to be understood that the application is not limited to the disclosed examples. To the contrary, the present application is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

[0093] All publications, patents and patent applications are herein incorporated by reference in their entirety to the same extent as if each individual publication, patent or patent application was specifically and individually indicated to be incorporated by reference in its entirety. Where a term in the present application is found to be defined differently in a document incorporated herein by reference, the definition provided herein is to serve as the definition for the term.

FULL CITATIONS FOR DOCUMENTS REFERRED TO IN THE DESCRIPTION

¹ Stephenson, R. E., Gutierrez, D., Peters, C., Nichols, M., & Boles, B. R. Biofouling, 2014, 30, 337.

² Zemek, K., Kosikova, B., Augustin, J., Joniak, D. Folia Microbiol. 1979, 24, 483.

³ Thakur, V.K., Thakur, M.K., Raghavan, P., Kessler, M.R. ACS Sustainable Chem. Eng. 2014, 2, 1072.

⁴ a) Nada, A.M.A., El-Diwanya, A.I., Elshafei, A.M. Acta Biotechnol. 1989, 9, 295; Dong, X., Dong, M., Lu, Y., Turley, A., Jin, T., Wu, C. Ind. Crop. Prod. 2011 , 34, 1629.

⁵ NCmez-Flores, R., Gimenez, B., Fernandez-Martin, F., Lopez-Caballero, M. E., Montero, M. P., Gomez-Guillen, M. C. Food Hydrocolloids, 2013, 30, 163.

⁶ Gregorova, A., Redik, S., Sedlaffk, V., & Stelzer, F. (201 1 ). Lignin-containing polyethylene films with antibacterial activity. In NANOCON 201 1 -Conference Proceedings, 3rd International Conference. TANGER Ltd.

⁷ Ma Y., Dai J., Wu L., Fang G., G. Zhanhu,“Enhanced anti-ultraviolet, anti fouling and anti-bacterial polyelectrolyte membrane of polystyrene grafted with trimethyl quaternary ammonium salt modified lignin” Polymer 2017, 114, 113.

Table 1 : Mechanical properties of lignin-polypropylene blends.

Note: Numbers in brackets are standard deviations.

Table 2

Not recorded.

Table 3: Recovered organisms from samples at Time = 24 hours.

CO

^* Untreated Control at Time = 0 hours, 8.54 ^c 10³ cells/cm².

Table 4: Recovered organisms from samples at Time = 24 hours.

_* Untreated Control at Time = 0 hours, 7.90 ^c 10³ cells/cm².

Claims

Claims:

1 . An antimicrobial plastic blend comprising a quaternary ammonium- modified, lignin-containing material dispersed in a plastic.

2. The antimicrobial plastic blend of claim 1 , wherein the lignin-containing material is lignin.

3. The antimicrobial plastic blend of claim 2, wherein the lignin is selected from Kraft lignin, soda lignin, organosolv lignin, a lignin from a biorefinery process and combinations thereof.

4. The antimicrobial plastic blend of claim 3, wherein the lignin is Kraft lignin.

5. The antimicrobial plastic blend of claim 4, wherein the lignin is a softwood Kraft lignin.

6. The antimicrobial plastic blend of any one of claims 1 to 5, wherein the quaternary ammonium is one or more quaternary ammonium cations of Formula I:

R¹

R⁴— N— R² (I)

R³ wherein R¹ , R², R³ and R⁴ are each independently selected from Ci-3oalkyl and C2-3oalkenyl.

7. The antimicrobial plastic blend of claim 6, wherein two or three of R¹ , R², R³ and R⁴ are each independently selected from Ci-4alkyl and the remaining one or two of R¹ , R², R³ and R⁴ are each independently selected from Cio-3oalkyl and Cio-3oalkenyl.

8. The antimicrobial plastic blend of claim 7, wherein R¹ and R² are each methyl and R³ and R⁴ are each independently selected from linear Ci2-24alkyl.

9. The antimicrobial plastic blend of claim 8, wherein the alkyl quaternary ammonium cation of Formula I is dimethyldioctadecylammonium cation.

10. The antimicrobial plastic blend of claim 6, wherein the one or more alkyl quaternary ammonium cations of Formula I is dehydrogenated tallow)dimethylammonium cation.

1 1 . The antimicrobial plastic blend of any one of claims 1 to 10, wherein the molar ratio between phenolic groups in the lignin-containing material and the quaternary ammonium cation is from about 1 : 1 to about 1 : 0.05.

12. The antimicrobial plastic blend of claim 1 1 , wherein the molar ratio is about 1 : 0.25.

13. The antimicrobial plastic blend of any one of claims 1 to 12, wherein the plastic is a polypropylene.

14. The antimicrobial plastic blend of any one of claims 1 to 13, wherein the antimicrobial plastic comprises from about 5% (w/w) to about 30% (w/w) of the quaternary ammonium-modified, lignin-containing material, based on the total weight of the antimicrobial plastic blend.

15. The antimicrobial plastic blend of any one of claims 1 to 14, further comprising one or more additives.

16. The antimicrobial plastic blend of any one of claims 1 to 14, wherein the antimicrobial plastic blend consists essentially of the plastic and the quaternary ammonium-modified, lignin-containing material.

17. The antimicrobial plastic blend of any one of claims 1 to 16, wherein the quaternary ammonium-modified, lignin-containing material is homogeneously dispersed throughout the plastic and on the surface of the antimicrobial plastic blend.

18. The antimicrobial plastic blend of any one of claims 1 to 17, wherein the blend is an antibacterial plastic blend.

19. The antimicrobial plastic blend of claim 18, having antibacterial activity against Gram-negative bacteria and Gram-positive bacteria.

20. The antimicrobial plastic blend of claim 19, wherein the Gram-negative bacteria is Escherichia coli and the Gram-positive bacteria is Staphylococcus aureus.

21 . A process for preparing a plastic compound for use in forming an antimicrobial plastic blend, the process comprising:

22. The process of claim 21 , wherein the lignin-containing material is lignin.

23. The process of claim 22, wherein the lignin is selected from Kraft lignin, soda lignin, organosolv lignin, a lignin from a biorefinery process and combinations thereof.

24. The process of claim 23, wherein the lignin is Kraft lignin.

25. The process of claim 24, wherein the lignin is a softwood Kraft lignin.

26. The process of any one of claims 21 to 25, wherein the quaternary ammonium is one or more quaternary ammonium cations of Formula I:

R¹

R⁴— N— R² (I)

27. The process of claim 26, wherein two or three of R¹ , R², R³ and R⁴ are each independently selected from Ci-4alkyl and the remaining one or two of R¹ , R², R³ and R⁴ are each independently selected from Cio-3oalkyl and Cio- 3oalkenyl.

28. The process of claim 27, wherein R¹ and R² are each methyl and R³ and R⁴ are each independently selected from linear Ci2-24alkyl.

29. The process of claim 28, wherein the alkyl quaternary ammonium cation of Formula I is dimethyldioctadecylammonium cation.

30. The process of claim 26, wherein the one or more alkyl quaternary ammonium cations of Formula I is dehydrogenated tallow)dimethylammonium cation.

31 . The process of any one of claims 21 to 30, wherein the molar ratio between phenolic groups in the lignin-containing material and the quaternary ammonium cation is from about 1 : 1 to about 1 : 0.05.

32. The process of claim 31 , wherein the molar ratio is about 1 : 0.25.

33. The process of any one of claims 21 to 32, wherein the plastic is a polypropylene.

34. The process of any one of claims 21 to 33, wherein the plastic compound comprises from about 5% (w/w) to about 30% (w/w) of the quaternary ammonium- modified, lignin-containing material, based on the total weight of the plastic compound.

35. The process of any one of claims 21 to 34, wherein the plastic compound further comprises one or more additives.

36. The process of any one of claims 21 to 34, wherein the plastic compound consists essentially of the plastic and the quaternary ammonium-modified, lignin-containing material.

37. The process of any one of claims 21 to 36, wherein the compounding comprises mixing the plastic, the quaternary ammonium-modified, lignin- containing material and the one or more additives, if present, at a molten stage of the plastic in a twin-screw extruder.

38. A process for preparing an antimicrobial plastic blend, the process comprising forming a plastic compound obtained by a process of any one of claims 21 to 37 to obtain the antimicrobial plastic blend.

39. The process of claim 38, wherein the forming comprises injection molding, extrusion, blowing, casting, calendaring, thermoforming or compression.

40. The process of claim 38, wherein the forming comprises injection molding.

41 . A process for preparing an antimicrobial plastic blend, the process comprising:

forming the plastic compound to obtain the antimicrobial plastic blend.

42. The process of claim 41 , wherein the forming comprises injection molding, extrusion, blowing, casting, calendaring, thermoforming or compression.

43. The process of claim 41 , wherein the forming comprises injection molding.

44. The process of any one of claims 41 to 43, wherein the lignin-containing material is lignin.

45. The process of claim 44, wherein the lignin is selected from Kraft lignin, soda lignin, organosolv lignin, a lignin from a biorefinery process and combinations thereof.

46. The process of claim 45, wherein the lignin is Kraft lignin.

47. The process of claim 46, wherein the lignin is a softwood Kraft lignin.

48. The process of any one of claims 41 to 47, wherein the quaternary ammonium is one or more quaternary ammonium cations of Formula I:

R¹

R⁴— N— R² (I) R³ wherein R¹ , R², R³ and R⁴ are each independently selected from Ci-3oalkyl and C2-3oalkenyl.

49. The process of claim 48, wherein two or three of R¹ , R², R³ and R⁴ are each independently selected from Ci-4alkyl and the remaining one or two of R¹ , R², R³ and R⁴ are each independently selected from Cio-3oalkyl and Cio- 3oalkenyl.

50. The process of claim 49, wherein R¹ and R² are each methyl and R³ and R⁴ are each independently selected from linear Ci2-24alkyl.

51 . The process of claim 50, wherein the alkyl quaternary ammonium cation of Formula I is dimethyldioctadecylammonium cation.

52. The process of claim 48, wherein the one or more alkyl quaternary ammonium cations of Formula I is dehydrogenated tallow)dimethylammonium cation.

53. The process of any one of claims 41 to 52, wherein the molar ratio between phenolic groups in the lignin-containing material and the quaternary ammonium cation is from about 1 : 1 to about 1 : 0.05.

54. The process of claim 53, wherein the molar ratio is about 1 : 0.25.

55. The process of any one of claims 41 to 54, wherein the plastic is a polypropylene.

56. The process of any one of claims 41 to 55, wherein the plastic compound comprises from about 5% (w/w) to about 30% (w/w) of the quaternary ammonium- modified, lignin-containing material, based on the total weight of the plastic compound.

57. The process of any one of claims 41 to 56, wherein the plastic compound further comprises one or more additives.

58. The process of any one of claims 41 to 56, wherein the plastic compound consists essentially of the plastic and the quaternary ammonium-modified, lignin-containing material.

59. The process of any one of claims 41 to 58, wherein the compounding comprises mixing the plastic, the quaternary ammonium-modified, lignin- containing material and the one or more additives, if present, at a molten stage of the plastic in a twin-screw extruder.

60. An antimicrobial plastic blend prepared according to a process as defined in any one of claims 38 to 59.

61. A use of the antimicrobial plastic blend as defined in any one of claims 1 to 20 as a surface for killing and/or inhibiting the growth of a microbe.

62. The use of claim 61 , wherein the microbe is bacteria.

63. The use of claim 62, wherein the bacteria are Gram-negative, Gram positive or combinations thereof.

64. A method of killing and/or inhibiting the growth of a microbe, the method comprising contacting the microbe with a surface of an antimicrobial plastic blend as defined in any one of claims 1 to 20.

65. The method of claim 64, wherein the microbe is bacteria.

66. The method of claim 65, wherein the bacteria are Gram-negative, Gram positive or combinations thereof.