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Document Type and Number:
WIPO Patent Application WO/2023/007435
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Disclosed herein is a biodegradable biopolymer composition and the method to prepare the same via mixing of humins and chitosan, wherein said humins were prepared by acid-catalysed dehydration of non-edible bio-waste materials. Also disclosed herein is a UV-absorbing film prepared using said biodegradable biopolymer composition.

Application Number:
Publication Date:
February 02, 2023
Filing Date:
July 28, 2022
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We claim,

1 ) A method to produce a biodegradable polymeric composition, comprising- a) Selecting chitosan sourced from non-edible marine wastes; b) Selecting a source of humins between sugars and non-edible bio refinery wastes; c) Subjecting the chitosan to a first sub-process to obtain a chitosan solution of strength 2% to 50% w/v; d) Subjecting the source of humins to a second sub-process to obtain purified humins; e) Adding 2% to 20% w/v of the purified humins and 1% to 50% w/v of a plasticizer, sorbitol in particular, to the chitosan solution to result in an admixture; and f) Subjecting the admixture to heating at a temperature of 70SC to 90SC over a period of 2 to 4 hours to result in a solution typified in having a viscosity of 20-2000cP, said solution being the biodegradable biopolymer composition ready for use.

2) The method to produce a biodegradable polymeric composition as claimed in claim 1 , wherein the non-edible marine wastes are selected among scales and exoskeletons of marine organisms.

3) The method to produce a biodegradable polymeric composition as claimed in claim 1 , wherein the non-edible bio-refinery wastes are selected between corn cobs and rice husk being used at a concentration of 5g in 100 ml in the second sub-process.

4) The method to produce a biodegradable polymeric composition as claimed in claim 1 , wherein the sugars are selected between Xylose and Glucose being used at a concentration of 1 .5 M in the second sub-process.

5) The method to produce a biodegradable polymeric composition as claimed in claim 1 and either one of the claims , wherein the first sub-process consists of- a) Dissolving 2% to 50% w/v, 1% w/v in particular, of chitosan in an organic acid selected from among formic acid, acetic acid, citric acid, and succinic acid to result in an admixture; b) Holding the admixture overnight at a temperature of 25°C to 35°C amidst continuous stirring using a magnetic stirrer to result in an homogenous admixture; c) Sieving the homogenous admixture using a tea sieve of pore size 740 to 250 pm to remove solid impurities and therein leaving a filtrate being the chitosan solution of strength 2% to 50% w/v, 1% w/v in particular.

6) The method to produce a biodegradable polymeric composition as claimed in claim 1 , wherein the second sub-process is typified in being an acid catalysed dehydration reaction and consists of- a) Charging the source of humins to an autoclave reactor; b) Adding catalyst, acetic acid in particular, to said autoclave reactor; c) Purging the autoclave reactor with nitrogen; d) Allowing acid catalysed dehydration of the source of humins to occur at 180°C to result in a reaction mixture; e) Filtering the reaction mixture using a filter paper to obtain a residue and a filtrate; f) Dissolving the residue in acetone to separate humins from unreacted waste and therein leave a first solid mass component; g) Evaporating the filtrate to leave behind a second solid mass component; and h) Subjecting the pooled first and second solid mass components to Soxhlet extraction to yield pure humins. 7) The method to produce a biodegradable polymeric composition as claimed in claim 5, wherein the organic acid is 1% Acetic acid.

8) The method to produce a biodegradable polymeric composition as claimed in claims 3, 4 and 6, wherein the organic acid is- a) 1% Acetic acid if the sugar is Xylose; b) 0.05M Sulfuric acid if the sugar is Glucose; c) 1% Acetic acid if the non-edible bio-refinery waste is corn cobs; and d) 1% Acetic acid if the non-edible bio-refinery waste is rice husk. 9) A film made via conventional solution casting method using the biodegradable biopolymer composition of claim 1 , the film characterized in having- a) Tensile strength ranging from 15.9 to 49.3 MPa; b) Contact angle ranging between 70.0° to 85.2° c) Moisture content of 5 to 26 %. d) Water solubility ranging between 10 to 75 %. e) 100% absorbance for UV-A, UV-B and UV-C; and f) Complete degradation in under 120 days when buried in soil.

Method for producing biodegradable polymeric films from biomass waste

Cross references to related applications: This complete specification is filed further to application for patent No. 202121019395 dated 28/07/2021 filed with a provisional specification, the contents of which are incorporated herein in their entirety, by reference.

Field of the invention

The present invention relates generally to the field of polymer chemistry and, in that, relates more particularly to a biodegradable polymeric composition, the method of preparing said biodegradable polymeric composition, and various applications including film, fiber and / or non-woven forms of said biodegradable polymeric composition.

Definitions and interpretations

Before undertaking the detailed description of the invention below, it may be advantageous to set forth definitions of certain words or phrases used throughout this patent document: the terms “include” and “comprise,” as well as derivatives thereof, mean inclusion without limitation; the term “or” is inclusive, meaning and/or; the phrases “associated with” and “associated therewith,” as well as derivatives thereof, may mean to include, be included within, interconnect, with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like. Also, before undertaking the disclosures to follow, it shall be advantageous to set forth definitions of certain words or phrases used therein, as under- “PLA” refers poly(lacic acid);

“PHA” refers polyhydroxyalkonates;

“PBS” refers poly(butylene succinate);

“PBAT” refers poly(butylene adipate terephthalate);

“Click chemistry” refers the class of biocompatible small molecule reactions commonly used in bioconjugation, allowing the joining of substrates of choice with specific biomolecules; “Food raw materials” refers materials of plant / animal / microbial origin which are capable of being used as food / ingredients to prepare food intended primarily for consumption by humans.

“ITO” refers Indium Tin Oxide

Background of the invention

Polymeric compositions are ubiquitously used to make a variety of disposable articles such as domestic consumables (for example, cling films, carry bags, cello tape, geo textiles, food / beverage containers etcetera), medical apparel (for example, surgical drapes, gowns / overalls etcetera), medical and / or sanitary supplies (for example, bandages, diapers, sanitary pads, incontinence products, wipes etcetera).

Co-achievement of breathability and water-imperviousness is the soul of the aforementioned applications. The polymeric compositions used to prepare these products are conventionally manufactured by blending organic (or inorganic) filler with a polyolefin-based resin. Flowever, the applicability of these polymeric compositions are restricted to them being liquid barriers designed to be discarded after a single time usage. Thus, it is an issue to overcome the lack of reusability while not compromising the duo of breathability and selective permeability when designing bio-safe and bio compatible workable polymeric compositions.

Another spectrum where polymeric compositions find applicability is agriculture, and in that specifically the use of mulching films for adding a layer to the surface of the soil around the plant with plastic film to conserve the soil moisture that suppress weeds growth, regulate soil temperature and prevent water loss through evaporation. Biodegradability is a critical property sought in the aforesaid agricultural applications, whereby the farmer does not have to laboriously collect the mulch films after harvest but can simply plow it in post-harvest, to therefore save time, money and efforts. Thus, it is an another issue to overcome the lack of biodegradability, counter or negate the aspects of biomagnification and / or pollution of the water table, when designing bio safe and bio-compatible workable polymeric compositions for such applications.

Also on a general note, the continually-dwindling fossil reserves, the associated environmental devastation and energy crisis have forced a paradigm shift towards renewable economy. Consequently, there is tremendous quest for sustainable alternatives in numerous fields and polymers are no exception to it. To note, the overall global plastic production in 2017 was 335 million tons with less than 10% being recycled and around 20% being incinerated for energy. Surprisingly, around 700,000 tons of plastics are used annually only for agriculture. The numbers are alarming which demand efficient waste management and disposal strategies to avoid environmental pollution. Hence, there is a global mass-scale demand for sustainable chemistry which can output biodegradable polymeric compositions fit for at least the aforementioned applications.

The concept of biodegradable polymers is not new. Prior art, to the extent surveyed, lists some scattered attempts to address the issues mentioned hereinabove. For example, PLA accounts for around 24% of the global production capacity for biodegradable polymers. Besides PLA, mainly starch blends (44%), PHAs (6%), biodegradable polyesters including PBS and PBAT (EcoflexU) (23%) are produced on an industrial scale. However, except the starch-based products, all other polymers are synthetic in origin which implies high manufacturing costs in addition to questionable biodegradability.

As known from classical theory, lignocellulosic materials obtained from wood and agro wastes consist of natural biodegradable polymers such as cellulose, hemicellulose and lignin in varying amounts. Similarly, marine / oceanic wastes such as those arising from processing of shelling / processing of crustaceans and mollusks contain a nitrogen containing biopolymer. Another source is lignocellulosic refineries which generate carbonaceous polymeric compounds obtained by acid-catalyzed dehydration of carbohydrates. Though said natural biodegradable polymers are theoretically abundant and also renewable, their potential for commercial production of biodegradable largely overlooked. Judicious strategies are sorely needed for utilization of said biopolymers and blends / composites thereof for different applications.

Oceanic waste polymer has been previously used for the synthesis of thin films with suitable modifications mainly for packaging (with or without barrier properties). However, the modifications are done either by “click chemistry” which is a tedious and energy intensive process or by using resources which have other potential applications e.g. in food and cosmetics. Composite films synthesized from the combination of these wastes have never been explored till date. Coming to the specific locus of the present invention, prior art mentions several approaches for synthesizing biodegradable films for mulching applications. The films are made by deploying synthetic polymers or bio-based polymers.. Among the synthetic polymers PBAT, PBS, PHA and PLA have an established market as mulching films (Hayes et at, Biodegradable plastic mulch films for sustainable specialty crop production, Chapter 2, Springer Nature Switzerland, 209). However, they are either partially degradable or costly. Starch is widely used among the bio-based materials for the synthesis of thin films owing to its ease of biodegradation (Lu et al eXPRESS Polymer Lett. 6, 2009, 366-375). It is blended with other polymers and fillers to enhance the physical properties in accordance with the application. There are reports of starch and chitosan blends for mulching applications as addition of chitosan reduces its water solubility and increases the mechanical and barrier properties (Merino et al. J. Polym. Environ, 27, 2019, 97-105). The fillers used are black pigments or nanoclay which improved the flexibility of the films (Merino et al. J. Polym. Environ, 27, 2019, 1959-1970). Gelatin is yet another polymer added to alter the starch matrix (Rosseto et al J. Sci. fd. Agric 2019). There are other interesting approaches in which films are made from waste biomass. Citric acid fermentation waste and PVA films were synthesized for agricultural uses (Ma et al, Int. Biodeter. Biodegr 111, 2016, 54-61). PVA induced hydrophobicity and increased mechanical properties making them apt for the application. Films comprising of industrial waste materials and linseed oil have also been reported (Virtanen et alJ. Polym. Environ DOI 10.1007/s10924-016-0888-y). Recently, Kelp mulching films were also explored expanding the scope of algal biomass (Zhao et al Algal Res. 26, 2017, 74-83). Visualizing this, it can be inferred that all dimensions of biodegradable polymers have been strategically explored for mulch film but use of carbohydrate waste polymer which is a potent biomass waste is overlooked, thereby preserving a an unaddressed niche for continued research in this domain.

Issues to be resolved

As can be broadly appreciated on basis of the foregoing narrative, the following issues are, besides others, of technical nature and otherwise, of concern and thus the basis for inception of the present invention- a) Lack of complete biodegradability; b) Lack of reusability; c) Technical complexities and undue costs of manufacturing; d) Lacking of avenue for use of readily available and cheap bio-wastes; e) Overlooking of carbohydrate wastes for production of biopolymers. Prior art, to the extent surveyed therefore, does not list a single effective solution embracing all considerations mentioned hereinabove, thus preserving an acute necessity-to-invent for the present inventor/s who, as result of focused research, has come up with novel solutions for resolving all needs once and for all. Work of the presently named inventor/s, specifically directed against the technical problems recited hereinabove and currently part of the public domain including earlier filed patent applications, is neither expressly nor impliedly admitted as prior art against the present disclosures.

A better understanding of the objects, advantages, features, properties and relationships of the present invention will be obtained from the following detailed description which sets forth an illustrative yet-preferred embodiment.

Objectives of the present invention

The present invention is identified in addressing at least all major deficiencies of art discussed in the foregoing section by effectively addressing the objectives stated under, of which-

It is an objective hereof to provide a polymeric composition and method to prepare the same.

It is another objective further to the aforesaid objective/s that the polymeric composition so provided is completely biodegradable.

It is another objective further to the aforesaid objective/s that the biodegradable polymeric composition so provided is prepared from non-edible bio-waste materials It is another objective further to the aforesaid objective/s that the method for manufacturing said biodegradable polymer is reliable, simple and cost-effective.

It is another objective further to the aforesaid objective/s that the polymeric composition so provided is capable of diverse applicability and for readily substituting conventional petroleum-based commodity polymers.

The manner in which the above objectives are achieved, together with other objects and advantages which will become subsequently apparent, reside in the detailed description set forth below in reference to the accompanying drawings and furthermore specifically outlined in the independent claims. Other advantageous embodiments of the invention are specified in the dependent claims. Brief description of drawings

In order to understand the invention and to see how it can be carried out in practice, preferred embodiments will now be described, by way of non-limiting examples only, with reference to the accompanying drawings in which-

FIG. 1 shows UV-vis spectra of humin containing films.

FIG. 2 contains two microphotographs showing fungal growth observed during biodegradation studies undertaken in accordance with the disclosures hereof.

FIG. 3 contains stress-strain curves for (A) Chitosan-Sorbitol films (B) Humin films. FIG. 4 contains X-ray diffractograms of (A) Chitosan sorbitol films (B) Humin films and (C) humins.

FIG. 5 are FTIR spectra of (A) Chitosan sorbitol films (B) Humin films FIG. 6 are Scanning Electron micrographs of (A) Humins (Xylose) (B) Film without humins (CHT:SFiB=70:30) (C) Film with 5% humins (D) Film with 7.5% humins (E) Film with 10% humins (F) Film with 12.5% humins FIG. 7 are AFM images of Control (0%), 5%H, 7.5%H, 10%H and 12.5%H FIG. 8 showcases Contact angle measurements of (A) Film without humins (CHT:SFiB=70:30) (B) Film with 5% humins (C) Film with 7.5% humins (D) Film with 10% humins (E) Film with 12.5% humins.

FIG. 9 shows TGA graphs of chitosan sorbitol films FIG. 10 shows Thermogravimetric analysis of humin containing films FIG. 11 are photographs showing Evidence of fungi growth (A. niger) on the surface of films with and without humins

FIG. 12 are Scanning electron micrographs of 5% humins film after (A) 21 days of incubation and (B) 28 days of incubation

Attention of the reader is now requested to the detailed description to follow which narrates a preferred embodiment of the present invention and such other ways in which principles of the invention may be employed without parting from the essence of the invention claimed herein.

Summary / Statement of the invention

The present invention teaches a biodegradable biopolymer composition and the method to prepare the same using chitosan sourced directly from the market or from non-edible marine waste materials and humins sourced via acid-catalysed dehydration of one among C5/C6 sugars such as xylose and glucose or non-edible bio-refinery waste materials such as corn cobs and rice husk.

Detailed description

The disclosures herein are based on the rationale of utilizing the natural polymers present in cheap, abundant and non-food bio-refinery and marine waste materials for the environmentally-sustainable as well as commercially-viable production of a completely biodegradable biopolymer composition suitable for mulching film and other applications.

Accordingly, the disclosures hereunder are directed to be best mode for performing the present invention which shall be regarded as exemplary for elaborating the essence of the invention claimed but not isolative nor restrictive whatsoever.

The present invention is implemented by following the underlying sequence of steps- a) Selection of input materials b) Preparation of a solution of chitosan sourced from non-edible marine wastes c) Preparation of humins from C5/C6 sugars or non-edible bio-refinery wastes d) Preparation of master batch of the biodegradable biopolymer composition e) Putting the master batch to desired application

It shall be understood by the reader, that the steps b) and c) above can be done in either sequence or be practiced in parallel, without affecting essence of the invention subject hereof.

Each of the above steps is now elaborated in detail as under- a) Selection of input materials- As to the chemicals needed for implementing the present invention, white vinegar was purchased from Kalvert Foods Pvt. Ltd. India. Sorbitol, glycerol, acetic acid, glucose, fructose and xylose were procured from Loba Chemie Pvt. Ltd. For casting of films using the biopolymer composition hereof, ITO glass plates (10cmx10 cm) were obtained from Global Nanotech Pvt. Ltd. India and were used directly without any modification. All the chemicals and materials were of research grade and were used after drying following standard procedures. For biodegradability testing of the biopolymer composition taught herein (and not performance of the invention itself), Aspergillus niger NCIM 501, Penicillium pinophilum NCIM 759, Chaetomium globosum ATCC 2605 and Gliocladium virens ATCC 945 were obtained from National Collection of Industrial Microorganisms, CSIR-NCL, Pune.

Biological ingredients involved in the performance of the present invention, and thus subject of compliance u/S. 6 of the Biological Diversity Act, 2002, were as provided in Table 1 below. Table 1

It shall be understood by the reader that chitosan is sourced from scales and shells (exoskeletons of marine organisms) of crab, lobster, shrimp and other crustaceans, and as such, is of marine waste origin, whether procured directly from third party manufacturers (as purified or semi-pure chitosan) or produced as an upstream process from actual marine wastes using chitosan-extraction procedures known and conventionally practiced in the art. b) Preparation of chitosan solution

Solution of chitosan was prepared by dissolving 2-50 wt % of the non-edible marine waste-sourced chitosan / market-sourced pre-isolated chitosan in an organic acid selected among formic, acetic acid, citric acid, or succinic acid. In the preferred embodiment, Chitosan was dissolved in 1% (wt/v) white vinegar (acetic acid) solution to form an admixture.

The aforesaid admixture was stirred overnight using magnetic stirrer at room temperature (25-35°C).The solution was sieved (using tea sieves of 20-60 mesh (pore size 740 to 250 pm) to remove solid impurities, thereby resulting in a filtrate which is chitosan solution for use as per the underlying portion of this disclosure. c) Preparation of humins from non-edible bio-waste materials

Humins were prepared by acid catalysed dehydration of monomeric C5/C6 sugars and non-edible bio-waste materials. The dehydration reaction was carried out using a 300 ml_ Parr autoclave reactor. The reactor was charged with sugars/waste and water, to which required amount of catalyst (acetic acid) was added. The reactor was purged with nitrogen and the reaction was carried out at the desired temperature. The detailed experimental conditions for each reactant are given in Table 2 below.

Table 2

After the acid catalysed dehydration reaction, the reaction mixture was subjected to filtration using a sieve / filter paper. The residue was dissolved in acetone (to separate humins from unreacted waste), the filtrate was collected and evaporated. The solid mass obtained thereafter was then subjected to Soxhlet extraction to yield pure humins. d) Preparation of master batch of the biodegradable biopolymer composition

2-20% wt/v of pure humins (filler) of step c) above and 1-50% wt/v plasticizer (sorbitol) were added, at room temperature (25-35°C), into the chitosan solution of step b) above. The resultant solution was heated to 70 S C to 90 S C (80 S C in particular) for 2 to 4 hours (3 hours in particular) to obtain a solution having a viscosity of 20-2000cP, which is the viscous master batch solution ready for use in the application intended, particularly being the production of films as per procedure outlined in step e) below. Experimental studies reported herein are for sample cases wherein proportion of plasticizer was varied between 100:0, 80:20, 70:30, and 60:40, and for optimum proportion of 70:30, the humins were added at a concentration of 2%, 5%, 7.5%, 10% and 12.5%. These studies are oriented to assess the effect of said ingredients on the efficacy of the end application intended (production of films as per procedure outlined in step e) below) with best mechanical properties. It was observed that 5% wt/v humins and 70:30 v/v sorbitol are best for said end-application. e) Application of biodegradable biopolymer composition

The viscous master batch solution reached in step c) above was poured on the ITO glass plate and dried at room temperature, so as to obtain thin films of said via the conventional solution casting method. (Solution casting method referred in X. Ma, C. Qiao, J. Zhang, J. Xu Macromol. 119 (2018) 1294-1297). Thin films were prepared by pouring said heated viscous solution on a glass plate admeasuring 10cm x 10cm such as to have a uniform spread which was left for drying overnight at room temperature. After complete drying the films were removed carefully without cracks and punctures to yield the final product.

Characterization studies-

Films prepared by the aforementioned technique were characterized by different techniques like X-ray diffraction, Fourier transform Infrared spectroscopy, UV-visible spectroscopy, Raman scattering, Scanning electron microscopy, Thermogravimetric analysis, Mechanical strength analysis, contact angle measurements and water absorption studies etc .The analytical results led to conclude that the films have good tensile strength, elasticity with excellent UV-absorption properties as shown in the FIG. 1 which showcased its potential as an effective mulch film. Details of these studies are described in detail, as hereunder- X-ray diffraction

X-ray diffraction patterns of humins and films were recorded on a PANalytical X'Pert PRO X-ray diffractometer. The data were collected with a step size of 0.02 ° at a scan rate of 0.5 °min- 1 . The incident radiation used was Ni filtered C K a (A= 1 .5406 A, 40 kV, 30 mA) and the data collection was carried out using a flat holder in Bragg- Brentano geometry (0.2 °). All the XRD patterns were collected in the range of 2Q = 3° to 80°. The XRD patterns of chitosan-sorbitol composite films are shown in FIG. 4A. The broad peaks observed at 2Q = 20° and around 2Q = 13° can be attributed to the anhydrous crystalline conformation of chitosan. The additional peak at 2Q = 10° originates from the variation in the degree of deacetylation, source of raw materials and film-forming method. With the addition of sorbitol, new peaks were observed in the region between 9-13° which is consistent with the pattern of the hydrated crystals. Increasing the amount of sorbitol, suppressed the crystalline nature of chitosan as evident from the reduction in the intensity of the peak at 20°. This decrease originates from the partial destruction of the chitosan structure and the variation in the inter-and intra-molecular hydrogen bonds. The shift in the 2Q towards lower values clearly supports these inferences.

XRD patterns of the films containing humins are shown in FIG. 4B. Addition of humins leads to further decrease in crystallinty as humins are amorphous in nature FIG. 4C. Researchers have demonstrated that humins are carbonaceous, heterogeneous macromolecules which do not have well defined structures thereby displaying a broad diffraction peak. With increase in the percentage of humins from 5-12.5% the intensity of the peak at 2Q = 20° corresponding to crystalline chitosan decreases sharply indicative of further transformation of polymer matrix. The presence of humins in the films can also be confirmed by the additional peaks obtained at higher 2Q values.

Fourier Transform infrared spectroscopy

The Fourier transform-infrared spectra of humins were recorded on a Bruker Tensor 27 FT-IR spectrometer under ambient conditions in DR mode from 400-4000 crrr 1 with 4 cm ~1 resolution. The spectra of the films were taken by using ATR mode over similar range as for humins.The FTIR spectra of chitosan and sorbitol films are shown in FIG. 5A. A broad band is seen to appear between 3600-3000 cm- 1 · and intensify as a function of sorbitol concentration. This band correspond to the stretching vibrations of the hydroxyl groups and symmetric or asymmetric stretching vibrations of the NH bonds of the amino groups. The absorption band at 1378 crrr 1 can be assigned to the CH2 bending of chitosan molecule. The band at 1500 crrr 1 confirmed the presence of -NH3 instead of -NH2. The band at 1200-1000 cm-' corresponds to the stretching of C-O-C bonds of the polymer backbone. FIG. 5B depicts the FTIR spectra of the films with humins (0, 5, 7.5,10 12.5%). The absorption band between 3500-3200 crrr 1 can be ascribed to the -OH stretching of carboxylic and phenolic groups. The band at 2800- 2950 cm ~1 corresponds to the symmetric and asymmetric stretching of the aliphatic - CH groups. The band between 1650-1610 cm-' represents the stretching vibrations of the phenyl conjugated C=C and C=0 bonds (Furan ring). The band -1440-1415 cm-' corresponds to the symmetric stretching of -COO- bending vibrations of aliphatic groups (-CH3 and -CH2) while the band between 1200-1000 cm-' is associated with the stretching of C-O-C bond of the polymer backbone and humins.

Scanning electron microscopy

The SEM micrographs of humins and films were obtained on a Leo Leica Cambridge UK Model Stereoscan 440 scanning electron microscope. The samples were coated with gold to prevent surface charging and also to protect from thermal damage due to electron beam. SEM micrographs of the films are presented in FIG. 6. The micrographs showed that the surface of chitosan-sorbitol films was smooth, homogenous and continuous revealing good miscibility and compatibility of sorbitol when incorporated into chitosan. Addition of plasticizer did not introduce porosity or discontinuities in the composite films. However, addition of humins altered the surface morphology as humins have a specific morphology and elemental composition which is dependent on the type of feedstock and processing conditions, Fig. 7 and Table 3 respectively. In presence of lower percentage of humins (5 and 7.5) the particles were dispersed and embedded uniformly in the film matrix but at higher percentages bigger particles were witnessed rendering heterogeneity to the films.

Table 3 Atomic force microscopy

Surface morphology measurements were performed by Nanosurf AFM in non-contact tapping mode. Data was acquired by Nanosurf easyscan 2. Roughness analysis was performed by SPIP6.3.6 developed by Image metrology. The average roughness (Sa) and root mean square roughness (Sq) of the films (Fig. 8) are given in Table 4.

Table 4

The average and root mean square roughness value for pristine film was lowest as it was homogeneous. On addition of humins, the roughness (Sa and Sq) increases which can be attributed to the heterogeneous nature and insolubility of humins in the polymer matrix. 5 wt% humins showed maximum roughness values (Sa = 6.0492 and Sq = 8.6086) which decreased thereafter with further addition of humins (7.5, 10 and 12.5 wt%) since in presence of lower amount, the particles of humins were present majorly on the surface but with increasing amount of humins they settled in the cavities of the polymer. The results are consistent with earlier findings.

Contact angle measurements

Contact angle measurements were performed on RAME-HART NRL-Model CA goniometer fitted with a Cannon camera. Doubly deionized water was used in this experiment. The Young’s equation gives the relationship between the contact angle Q, liquid-vapor surface tension g 1n , solid-vapor surface tension y sv and solid-liquid surface tension y sl .

Y lv cos0 = r sv - Ysl

Surface properties of plasticized chitosan films were evaluated from the contact angle measurements. Addition of plasticizer is known to induce hydrophilicity and hence the contact angle is expected to decrease, accordingly the contact angle of the 70:30 composite film is observed to be lower than the chitosan film. Further, the influence of humins on the surface properties of the films were elucidated from the contact angle measurements. As noted from FIG. 8, the composite film with 70:30 ratio of chitosan to sorbitol had a contact angle value of 85.2° which decreased to 77.4° and 70.0° after addition of 5 and 10% of humins respectively. These results imply the hydrophilic nature of the humins which arises due to the condensed aromatic nature with high functionality (evident from the EDAX analysis). With further increase in humin concentration to 12.5% the value increased to 73.8° which indicates that 10wt% is the threshold value beyond which due to agglomeration of particles at surface decreases the hydrophilicity.

Thermogravimetric Analysis

Thermogravimetric measurements of the films were performed with a Simultaneous Thermal Analyzer SDT-650 apparatus. The analyses were carried out in air (40 mL.min-1) at a heating rate of 10 °C min-1 from room temperature to 800 °C. Thermogravimetric analysis was undertaken to investigate the changes in the thermal stability of the films. Fig 9 represents the TGA curves of chitosan and sorbitol composite films. All the films showed a similar thermal degradation behavior with an initial small weight loss of ~ 12.66% between 30-155 °C due to loss of surface water. The second weight loss of about 10.2% between 155-250 ° could be due to the expulsion of intrinsic water. The major weight loss of 43.54% observed between 250 to 400 °C was related to the degradation of the polymer (chitosan) and the plasticizer i.e. sorbitol. The 7.38% residue could be attributed to the carbon and other inorganic impurities which are stable up to 900 °C. The decomposition temperature of the composite films was nearly invariable with varying concentration of sorbitol in the films. Incorporation of humins improved the thermal stability of the films in comparison to the control film, (Fig 10), humins containing films showed lower weight loss due to water as these moieties occupy the cavities lowering the intrinsic water content. Weight loss from 250-800 was higher in humins containing films which can be attributed to its complex polymeric degradation process owing to its macromolecular nature. However, no particular trend was observed with variation in humins content.

Water absorption studies

Water solubility and moisture content were determined by gravimetric method. The rectangular films (1x4 cm 2 , mass-Mi) were dried (105 S C, 24 h) to achieve a dry mass (M2). The films were then immersed in distilled water for 24 h at room temperature to obtain a constant mass (M3) followed by drying (105 S C, 24 h, mass- M4). The parameters were calculated using the formula given below Moisture content = [(M1-M2)/ M2] x 100 %

Water solubility = [(M2-M4)/ M4] x 100 %

The data of the physico- chemical properties such as thickness, moisture content and water is given in Table 1 . The thickness of the pristine chitosan film is 70 pm which is seen to increase with the addition of sorbitol. This could be explained in terms of the solid content of film forming solution. As the content of sorbitol increased, solid content also increased which probably affects the thickness of the film. The moisture content of the films increases with the addition of sorbitol, Table 1 . The neat chitosan film shows lowest moisture content. As content of sorbitol varies from 0 to 40% the moisture content increases from 5 to 26 %. Similarly water solubility also enhances from 10 to 75 %. This result is associated with the hydrophilic nature of the sorbitol. Furthermore, the addition of humins to optimized (CH: SOR=70:30) decreased the moisture content and water solubility of the films owing to heterogeneity of humins with the polymer matrix. This is because of the less space available for the moisture to be trapped in the film matrix.

UV-Visible spectroscopy

Percent transmittance of the films was recorded on a UV- Visible Spectrophotometer (Shimadzu, UV-3600) in the wavelength range of 200-800nm. A potential application for humins containing films is to be used as biodegradable UV blocking films for light sensitive product packaging and mulching. The UV blocking properties of the films is shown in terms of the % transmittance of the films in Fig. 7. Neat chitosan films exhibited moderate UV barrier properties towards UVA range (320-400 nm) and UVB light (280-320nm). Addition of humins (5-12.5 wt%) in the films resulted in 100% UV absorption (UVA, B and C (280-200). This excellent UV-blocking performance was attributed to the polymeric furanic structure of the humins. The color introduced by humins additionally influenced the transmittance of the films in the visible region. With the increase in humins from 5-10 wt% the visible absorption increased and then decreased for 12.5 wt% due to agglomerated larger particles. Consequently, with the addition of humins the transparency of the films altered resulting in darker films with increasing content of humins. The effect of types of humins on UV absorption was also investigated and the results are shown in Fig 11. It can be seen that humins obtained from different feed stocks (xylose, corncob, glucose, rice husk) exhibited excellent UV- barrier properties. Amongst them, the inferior shielding performance of humins derived from glucose can only be attributed to its larger particle size, as witnessed in SEM, since the chemical nature remains identical as observed in FTIR and Raman. This leads to inferior dispersion in the polymer matrix deteriorating its shielding performance.

Biodegradation studies

Biodegradation was feasible using fungi. ( Aspergillus niger following ASTM G21 -09 Standard Practice for Determining fungal decay / degradation). The growth of the fungus was clearly visible, as seen in FIG. 2. From the above studies it was inferred that through the invention it would be possible to obtain good quality thin films from biomass waste eradicating the dependence on edible biopolymers and plastics.

For the biodegradation studies the following protocol was adopted -

Potato-dextorse agar media preparation- Potatoes (200 g) were peeled and cut into cubes. Approximately 800 ml_ distilled water was added and allowed to boil for 30 min. It was further filtered through a muslin cloth, to the filtrate, glucose (20 g/L), yeast extract (0.1 g/L), and agar-agar (20 g/L) were added. The media was autoclaved at 121°C for 15 min.

Growth of Fungal cultures Slants were obtained and suitable stock cultures were prepared for experimentation. Spore suspension was prepared by scraping the pores and suspending in saline using Tween 80 (0.05%). The counts were measured using a counting chamber (Neubauer) and the final count ranged between 1 ,000,000 - 200, 000 spores/ml

Detailed Procedure- Sufficient potato-dextrose agar was poured into suitable sterile dishes to provide a solidified agar layer from 3 to 6 mm (1/8 to V4 in.) in depth. After solidification, the specimens were placed on the surface of the agar. The surface was inoculated, including the surface of the test specimens, with the composite spore suspension by spraying the suspension from a sterilized atomizer such that the entire surface is moistened with the spore suspension. The inoculated test specimens were covered and allowed for incubate at 28 to 30°C (82 to 86°F) with 85 % relative humidity. The standard length of the test was 28 days of incubation. The test may be terminated in less than 28 days for samples exhibiting a growth rating of two or more. Observations were made based on the visible effects and rated as per scale outlined in Table 5 below.

Table 5 Biodegradation of polymers involves several steps: (1) attachment of microorganisms at the surface of the polymer, (2) growth of microorganism, utilizing polymer as the carbon source and (3) primary degradation of the polymer followed by ultimate degradation. Table 3 shows the rate of fungal growth on the films without and with humins. The fungal growth is clearly visible on the films, although higher on the films containing humins (Fig. 11). Since, humins are antifungal in nature and rich in carbon increased fungal colonies can be witnessed on the films with humins. The morphological changes of the film samples during biodegradation test through fungal colonization were studied by SEM analysis. Fig. 12 shows the fungal colonization on the surface of the film pieces. The SEM images clearly showed the spores of fungi and growth of Aspergillus Niger colonies on the films implying the tendency of the films for biodegradation. Assessment of fungal growth for composite films was observed as per ratings in Table 6 below.

Table 6 Biodegradation study in soil

The biodegradation of the films was investigated by soil burial method. The films were cut into 2 cm x 2 cm size and buried in the soil, under ambient temperature (~25° C) and humidity conditions (70-80%). Water was sprayed twice a day to maintain the moisture of the soil. The films were removed at a time interval of 8 days, washed with distilled water followed by drying at 50 ° C for 24h. Observations are shown in Table 7.

Table 7 As observed from the table, the film with 5 % humins showed 21.95 % of degradation in 24 days. Therefore it will be expected that complete biodegradation approximately in 120 days.

Tensile Testing In order to evaluate the mechanical properties, the films (4 samples from each film) were cut according to ASTM standards. Tensile strength and elongation at break of the films were evaluated on a RSA3 TA instrument (USA), at 0.05 cm/min speed. Stress and strain data were gathered, and the maximum stress (at break) and breaking strain were recorded.

Typical stress-strain curves of chitosan-sorbitol films are shown in Fig. 3. Pure chitosan films were least stretchable. Blend films exhibited increased plastic deformation clearly elucidating the role of sorbitol as a plasticizer. The tensile strength and the elongation (E%) at fracture (TS) for the films are shown in Table 8 below.

Table 8 - Physico-chemical properties of the films (CHT=chitosan, SRB=sorbitol, TS=tensile strength at fracture, E=elongation at fracture)

In absence of sorbitol, E% of only 9.4 was obtained, that is the films were brittle. With the increase in the ratio of sorbitol from 20 to 40 the E% values increased from 44.4 to 65.5. This may be due to the chain flexibility introduced by the sorbitol moieties thereby reducing the native rigidity of chitosan. However, tensile strength is inversely correlated to elongation. With an increase in the ratio of sorbitol from 100:0 to 60:40, the tensile strength increases from 15.9 to 49.3 MPa respectively. This can be attributed to the weakening of the intermolecular forces between the chains of adjacent macromolecules, by the plasticizer thereby increasing the free volume together with decrease in the mechanical strength [49,50]. The moisture content of the films increases with the concentration of plasticizer due to its hygroscopic nature which adds to the diminished intermolecular forces. The ratio of 70:30 was found to be optimum yielding films with good tensile strength and flexibility, hence, further studies with addition of humins was considered for this composition. The highest tensile strength and elongation at break has been observed for the film with 5 % humins. Further, addition of humins reduced the mechanical properties due to agglomeration of particles of humins.

Film thickness

The thickness of the samples was measured using a digital micrometer MDC SX (Mitutoyo, Japan). Thickness was measured randomly at ten different points for each film, mean values were calculated and reported in pm.

Industrial applicability

The present invention is directed to the valorization of non-food bio-refinery and marine waste for production of UV-absorbing films for mulching and / or packaging applications. The application of the invention intends at its utilization as mulching films for retaining the soil temperature, humidity and weed control. Additionally, it can be used as UV protective products for packaging, paints, pigments etcetera. The industry would be benefitted, as the present invention will combat plastic pollution problem. The mulch films presently prepared from polyethene would be eradicated. It will also replace the currently used biodegradable mulch films prepared from edible starch by the ones prepared from nitrogen containing waste polymers which would enhance soil fertility after degradation.

The present invention has a sustainable approach and global impact due to its utility being underlined by its following salient features- a) Total replacement of edible biopolymers with non-edible ones, to thereby bias on selective exclusion of food raw materials; b) Freedom from conventional dependency on plastics and associated negative attributes; c) Dual benefit in terms of economy by lowering the manufacturing costs of polymers while simultaneously easing the waste disposal and management problems associated with conventional polymers; d) Beneficial and commercially-viable reutilization of biomass wastes; e) Substitution of conventional plastics, to thereby curtail the issues associated with production, handling and disposal of conventional plastics; f) Rationalizing existing technologies, such as mulching films etcetera, without risks of environmental pollution otherwise incidental to use of conventional plastics.

As will be realized further, the present invention is capable of various other embodiments and alterations without departing from the basic concept of the present invention. Accordingly, the foregoing description will be regarded as illustrative and not as restrictive whatsoever. Modifications and variations herein are intended to come within ambit of the present invention, which is limited only by the appended claims.