DESC:

PLANT BIO-WASTE BASED SYNTHETIC BIODEGRADABLE POLYURETHANE LEATHER AND METHOD THEREOF

WINNER NIPPON LEATHERETTE PVT LTD
PLOT NO. 83, HIPSIDC
INDUSTRIAL AREA, (SFS), BADDI,
HIMACHAL PRADESH-173205
INDIA
Contact No. 1795 245541-42
E-mail id: info@winnernippon.com

The following specification particularly describes the invention and the manner in which it is to be performed
FIELD OF INVENTION
The present invention generally relates to biodegradable synthetic or artificial leather. More specifically it pertains to plant bio-waste based synthetic biodegradable polyurethane leather and method thereof.

BACKGROUND OF THE INVENTION

Leather is one of the oldest and most traded commodities worldwide. Leather is a strong, flexible and durable material obtained from tanning or chemical treatment of skin/hides of various animals such as cattle, sheep, goat, pig etc., in order to prevent it from decay. Such leather is called Natural Leather.
Demand of leather is quite high because of its increased utilization in fashion industry especially for manufacturing of footwear, furniture and interior design industry as well as automotive industry (https://www.ibef.org/exports/leather-industry-india.aspx). India is 2nd largest producer of footwear and leather garments and accounts for 13% of world’s leather production.

Problem in Natural leather producing industries.
There are primarily two problems in Natural Leather Production. Firstly, they lead to animal abuse and killing and secondly, they cause environmental pollution.

Animal Abuse and killing- According to www.peta.org, global leather industry slaughters more than billions of animals every year and tan their skins for leather production. Moreover, the animals also undergo cruel treatment during transportation, sheltering, feeding and slaughtering.
(https://www.peta.org/issues/animals-used-for-clothing/animals-used-clothing-factsheets/leather-animals-abused-killed-skins/).

Environmental Pollution - Leather industry is one of the most polluting industry as tanning of animal skin and hides require various different chemical substances such as cyanide, chromium, coal-tar derivatives, and mineral salts etc., which are dangerous for human health and are difficult to dispose off from the environment (https://www.peta.org/issues/animals-used-for-clothing/animals-used-clothing-factsheets/leather-animals-abused-killed-skins/)
Moreover, leather tanning industry wastes about 15,000 gallons of water and leads to accumulation of 2,200 pounds of solid waste (such as animal’s hairs, flesh waste, keratin waste etc.) for every ton of leather produced. (US Patent application no. US 20130337711A1)

Existing commercial approaches to overcome the problem of Animals abuse/killing and environmental pollution

The Commercial approaches are as below:
1. Preparation of Synthetic Leather- Synthetic leather is also known as artificial leather, faux leather, imitation leather or vegan leather. Synthetic leather is prepared using poly vinyl chloride (PVC) or poly urethane (PU), microfibers or silicon material. The faux leather has similar appearance as that of natural leather but has less stretch ability and less breathability, moreover this type of leather is non-biodegradable and involve use high amount of toxic chemicals such as Di-methyl form-amide which possesses negative impacts on human health and environment when used in high concentrations.

2. Preparation of Leaf leather: Leaf leather is a type of biodegradable leather that can be prepared using leaves of various plants such as pineapple plant, teak tree leaves or from leaves of any other tree leaves. But leaf leather is not that durable, stretchable and strong as natural or synthetic leather is hence its manufacturing is limited.

3. Biodegradable Polyurethane based leather- Many approaches are there to manufacture biodegradable polyurethane leather by using natural woven or non-woven natural fiber such as hemp, jute, cotton, kenaf etc., as a base material, this solves the problem of biodegradability but still a large amount of DMF is utilized for manufacturing of this type of leather and the plastic layer impregnated over the base layer is still non-biodegradable.

4. Plant material based synthetic leather- Various other types of synthetic leather is also manufactured by incorporating citrus peel extract, plant extracts, plant-based bio augmentation material such as starch, vegetable oils, natural plant oil, sucrose etc., in polyurethane layer in order to enhance the breathability as well as biodegradability of the leather, but using these processed plant-based materials increases the cost of production as well as the cost of final product.

Problem solved by the present invention
Manufacturing of synthetic leather suffers from various problems such as lack of biodegradability, low tear and flex strength, high cost, use of hazardous chemical. The present invention overcomes the drawbacks of above cited problems as present invention discloses an innovative approach of incorporating natural waste plant powder (reinforcement material) prepared from fallen ground leaves/ sugarcane bagasse/ paddy straw into polyurethane based top layer and then impregnating this layer over biodegradable base layer prepared from natural fabric (such as hemp/cotton/polyester/viscose) in order to enhance the bio degradability, tear and flex resistance etc., of the synthetic leather. The present invention involves utilization of fallen ground leaves/ sugarcane bagasse/ paddy straw for preparation of synthetic leather which otherwise are sent to dumps, discarded or burnt and in turns results in emission of harmful gases such as methane, carbon monoxide, dioxins, etc., which contributes to global warming.
Thus, the present invention discloses an innovative approach of using natural waste plant powder, low cost and less wastage at the large production level of the manufacturing of synthetic leather which is novel in terms of prior art stated below.

Advantages offered by present invention
i. Highly Biodegradable: The present invention overcomes the problem of biodegradability as present invention uses a natural waste plant powder in a specific quantity for preparation of polyurethane layer and further impregnating this layer over natural and polyester fabric base material. Hence the synthetic leather disclosed in present invention is highly biodegradable.
ii. Overcomes the problem of harmful chemicals- Unlike natural and other synthetic leathers, the leather disclosed in the present invention uses very less chemicals and high amounts of natural waste so it is environmentally friendly.
iii. Better quality leather- The leather revealed in the present invention is of homogeneous quality, consistency in chemical composition and mechanical properties such as lightweight, high strength, high tear resistance, high flexibility, age resistance, soft to the touch so it can be used in the fashion industry, textile industry, automotive industry etc.
iv. Conversion of waste into valuable product- The present invention involves the utilization of roadside fallen leaves and agro-waste of plants for the preparation of synthetic leather at large production level, which would otherwise be dumped, discarded or burnt and results in harmful gases such as methane, carbon monoxide, dioxin etc., being emitted which contributes to global warming. The present invention reveals an innovative approach of utilizing plant bio-waste, especially of leaves, for the preparation of synthetic leather.
Prior art
Patent Application No: WO2021/099565 A1 discloses “Synthetic Leather of vegetable origin”
The above cited patent discloses an artificial leather, which comprises of two layers, the base layer is made up of opuntia or hemp fiber and acts as a support for leather formation and the upper layer is made up of vegetal powder fraction (Extracted from citrus pulp or peels of prickly pear), polyurethane and bonding agent (polylactic acid or cellulose acetate). The process consists of steps of extraction of powder from vegetal source, mixing of obtained powder with polyurethane and spreading of the mixture on vegetal origin support in the present of glue/bonding agent.
Present invention involves the use of simple leaf powder instead of citrus peel extract powder for preparation of polyurethane based synthetic layer. Further the process of wet coagulation and transfer coating is not disclosed in the above cited patent.

Patent Application No. WO2021203102A1 discloses “Biodegradable synthetic leather produced from recycled material”
The synthetic leather disclosed in above cited patent is made up of three layers i.e., Biodegradable layer made up of polyurethane and plant based biodegradable additive, which increases the biodegradability of the synthetic leather based product, Backing layer provides mechanical support to the biodegradable layer and is made up of recycled plastic fiber or non-woven fibers and Adhesive layer which binds the backing layer to the biodegradable layer, bio-based glue, natural adhesive can be used as adhesive layer, or heat treatment can also be used for binding of backing and biodegradable layer. Plant based biodegradable additive may include starch, bio-augmentation compounds etc. and may exist in the form of powder or liquid (solvent based).
The synthetic fiber disclosed in present invention is composed of hemp fiber, which acts as a base to support the plastic layer and the plastic or upper layer is made up of Polyurethane, (Dimethyl fumarate) DMF and natural leaf powder to enhance the biodegradability whereas the above cited patent discloses the use of starch or bio-augmentation material for preparation of biodegradable plastic layer. Moreover, the above cited patent discloses use of plastic fiber as base material whereas present invention involves the use of natural plant-based fiber i.e., hemp fiber for production of synthetic leather.

Patent Application No. EP3135809A1 discloses “Polyurethane synthetic leather and polyurethane film comprising sucrose and method for preparing the same”
The above invention relates to a method for preparing a polyurethane synthetic leather having uniform fine pores by coagulating a polyurethane mixture solution prepared by mixing an additive containing sucrose with a polyurethane resin composition and further removing the additive by washing. Coagulation is carried out by using a coagulation solution comprising organic solvent. Further the prepared leather undergoes a washing step to remove the additive. The synthetic leather is finally dried and ready for use. The process is disclosed in figure 2 as prior art fig.
In contrast, the present invention involves addition of natural leaves powder to the polyurethane and DMF layer in order to enhance the biodegradability as well as to decrease the amount of DMF whereas above cited patent discloses addition of sucrose to the polyurethane resin. The present invention involves use of double coagulation for leather formation whereas in above cited patent, single coagulation is used.

Patent Application No. US 7,306,825 B2 discloses “Process to make synthetic leather and synthetic leather made therefrom”
The above cited patent discloses a process of preparation of synthetic leather using aqueous polyurethane dispersion. The method comprises of steps of impregnating non-woven or woven textile with polyurethane dispersion consisting of non-ionizable polyurethane and external stabilizing surfactant and further exposing the impregnated textile to water containing coagulant for coagulation of the leather.
Present invention discloses a synthetic leather, which is biodegradable as it comprises of natural leaf powder based polyurethane layer, whereas the above cited invention does not disclose the utilization of natural leaf powder for production of synthetic leather.

Patent Application No. US2013033771A1 discloses “Composites having leather like characteristics”
The above cited invention discloses use of bio-based material such as plant oils and natural fibers to provide substitute for leather material. Natural fibers such as flax, kenaf, hemp, cotton fiber etc. is used along with curable resin comprising natural plant oil (triglycerides) such as soy oil, linseed oil, and their fatty acids. The method of leather formation comprises of steps of impregnating natural fiber with curable resin comprising bio-based compound by spreading the curable resin over the natural fiber, hot pressing of the curable resin and natural fiber in moulds and further degassing in the vacuum.
The present invention involves use of natural leaf powder based polyurethane layer (resin) for synthetic leather preparation, whereas the above cited patent involves the use of plant oils based polyurethane layer. Moreover, the wet coagulation process is not disclosed in the above cited patent.

Patent application no. US20210189642A1 discloses “Composition consisting of plant material having cellulose, in particular from waste products of apples, for producing a laminate, method for producing a laminate from plant material having cellulose, in particular from waste products of apples, and laminate produced by said method”
The above cited patent discloses a method of preparation of artificial leather comprising polymer i.e., polyurethane and plant powder with cellulose i.e., apple bio-waste. Above cited invention discloses certain steps for formation of artificial leather i.e., preparation of fiber based base layer, applying polymer and apple waste powder layer over base layer, levelling, coagulation and drying the obtained composition.
Present invention differs from the above invention, as present invention involve use of fallen leaves powder for preparation of synthetic leather. Moreover, present invention involves utilization of double coagulation method and transfer coating technique for leather formation, whereas above cited invention involves use of single coagulation technique.
Patent Application No. US2021/0114334A1 discloses “Natural Non-Woven Materials”
The above cited invention discloses a non-woven material comprising multilayered stack with interconnected layers. The layers are composite fiber material having 80-100% leaf of stem fiber from pineapple plant and 0-20% polymer. The process for same comprises of steps of formation of stack with plurality of layer of leaf fiber, interconnecting plurality of layers together by air laying technique to form non-woven multilayered mat, applying polymer (fusible material) to the mat, pressing or heat treatment to fuse fusing material with non-woven material, applying curable material and curing the curable material to prepare Artificial leather. The same is commonly sold under brand name “PINATEX” (https://www.ananas-anam.com/about-us/)
After pineapple harvest, the leftover plant leaves are collected in bundles and the long fibres are extracted using semi-automatic machines. The fibres are washed then dried naturally by the sun or drying ovens. The dry fibres go through a purification process to remove any impurities which results in a fluff-like material. This fluff-like pineapple leaf fibre (PALF) gets mixed with a corn based polylactic acid (PLA) and undergoes a mechanical process to create Piñafelt, a non-woven mesh which forms the base of all Piñatex collections. The Piñafelt is coloured using GOTS certified pigments and a resin top coating is applied to give additional strength, durability and water resistance. A foil is heat pressed on to create the Metallic collection and a high solid PU transfer coating is used to create Piñatex Performance.
Present invention differs from the above cited patent as present invention involves utilization of fallen leaves for preparation of artificial leather whereas above patent discloses use of pineapple leaf fiber for preparation of artificial leather.

Journals, Books and Publications
Saurabh, Shahnaz Jahan and Anjana; Artificial leather- An Eco-friendly alternative textile material for leather; International Journal of Educational Research and Technology; volume 9[1], March 2018; pp 46-54
The above cited paper discloses a method for preparation of artificial leather. The preparation step comprises of steps of preparation PU solution by addition of DMF ,preparation of coating solution, coating of the coating solution on the release support i.e., paper or glass film, impregnating non-woven or woven fabric with impregnating solution, coagulating the same by immersing in liquid which is non-solvent for polymer, wet-treated fibrous substrate is obtained, which is then applied to the surface of the coating layer and pressed lightly, material obtained is further immersed and coagulated in a coagulating liquid for a definite time at a definite temperature, to obtain a micro-porous structure of coating layer, The release support is stripped from the surface of the coating layer and the solvent which is contained in the coating layer and wet-fibrous substrate is extracted and washed and then dried.
The Polyurethane layer disclosed in present invention comprises of natural leaves powder, which enhances the biodegradability of the synthetic leather, whereas the above cited patent just discloses a simple wet coagulation process, for preparation of synthetic leather. Hence present invention differs from above cited research paper.

Pavan Paraskar et.al, Vegetable oil based polyurethane coatings- A sustainable approach – a review; Progress in Organic Coatings Volume 156, July 2021, 106267
The above cited review discusses about the replacement of petroleum based polyurethane coatings by green polyurethane-based coatings comprising bio-based material such as vegetable oils and their derivatives such as methyl ester, fatty acids and other bio-renewable sources. The review discusses different chemical modifications to convert bio-based precursors to polyols and isocyanates.
The above cited review does not disclose a method of preparation of synthetic leather using leaves powder polyurethane layer

Leaf Leather; Author: Joe (https://treetribe.com/blogs/tree-tribe-vibe/what-is-leaf-leather)
Leaf leather is innovative plant-based leather made from tree leaves. The process comprises of steps of harvesting fallen teak tree leaves, soaking leaves in water, dying and arranging flat together and allowed to dry, which bonds the leaves together, the leaf layer is further mended with cotton fabric to provide soft backing and structure, a thin translucent outer layer made of non-toxic BOPP film is applied that seals the leaf layer and protect it while maintaining the texture of the leaves.
Present invention is increasing the flexibility and bio-degradability of PU-based synthetic leather by addition of bio-based leaves powder over the natural hemp fiber and further wet- coagulation of the same for preparing leather like material, whereas the above cited data discloses a method for providing base support and laminating layer over the fallen leaves in order to prepare synthetic leather.
Present invention involves the use of natural hemp fiber as a base material and the Polyurethane layer and waste leaves powder, which enhances the bio-degradability of the synthetic leather. The sustainability, economic growth and performance are important factor influencing the future prospects of the synthetic leather. In order to expand the use of waste leaves powder and natural hemp fibers in synthetic leather with various applications and properties that must be somewhat comparable with materials such as metals and petrochemical derivatives. However, the price of waste leaves powder and natural hemp fibers is much lower than that of synthetic fibers. The specific strength and modulus of natural hemp fibers are similar to those of synthetic fibers but surface properties are higher.
From the above it is clear that none of the prior art discloses or anticipates the product of the present invention.

OBJECT OF THE PRESENT INVENTION
The main object of the present invention is to disclose natural plant bio-waste based synthetic polyurethane leather which has much better biodegradability than existing synthetic leathers.
Another object of present invention is to disclose natural plant bio-waste based synthetic leather, which is light weight and possesses high tear strength and high flexibility.

SUMMARY OF THE INVENTION
Present invention discloses natural plant bio-waste based synthetic biodegradable polyurethane leather and method thereof. Natural Plant bio-waste such as fallen leaves or agro-waste such as sugarcane bagasse or paddy straw mechanically converted into powder form. The inventors have named this synthetic biodegradable polyurethane leather as “Flora” and will be referred as “Flora” herein after. It is developed by coagulation method using natural fabric (such as hemp/cotton/viscose) and polyester fabric as a base material and polyurethane resin. The top layer consisting of natural plant waste powder on the coagulated fabric is impregnated which enhances biodegradability, chemical and physical properties giving excellent chemical resistance and softness.
In the coagulation step, the polyurethane-based mixing solution is completely coagulated by immersing a coagulation solution containing DMF and softener water in a ratio of 20:80.
Fully compacted synthetic leather is further washed using hot R/O water, heated, cooled and undergoes a transfer coating process for the final finishing of the prepared leather.
The synthetic leather produced in present invention possesses excellent tensile strength i.e., 14.75- 16 N/mm2 and Flex resistance i.e., 200000-300000 Flex Cycles to Grade = 2.
Moreover, the present invention involves utilization of natural waste plant powder such as fallen ground leaves or agro-waste such as sugarcane bagasse and paddy straw which otherwise are sent to dumps, discarded or burnt and in turns results in emission of harmful gases such as methane, carbon monoxide, dioxins, etc., and contributes to global warming. Present invention discloses an innovative approach of using natural plant bio-waste including leaves, sugarcane bagasse or paddy straw for preparation of synthetic leather which is novel in terms of stated prior art.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig 1: Prior art figure
Fig 2: Prior art figure
Fig 3(a- e): Macroscopic images have shown the uniform distribution of different types of particles in the flora matrix.
Fig 4 (a-c): Failure analysis of natural leaf particles in the flora matrix after tear strength testing (a) SEM image strong interface bonding between fabric and flora matrix, (b) SEM-EDS image of chemical analysis of tree leaf reinforced Flora and (c) SEM-EDS image of chemical analysis of sugarcane bagasse reinforced Flora.

DETAILED DESCRIPTION OF THE INVENTION
The present invention discloses an innovative approach of incorporating natural reinforcement material i.e., leaf powder made from fallen ground leaves or agro waste such as sugarcane bagasse or paddy straw, into polyurethane and DMF based top layer and then impregnating this layer over biodegradable base layer prepared from natural fabric in order to enhance the biodegradability, breathability, tear and flex resistance etc., of the synthetic leather. Dual coagulation process using partially and completely coagulation along with transfer coating process is done for the preparation of superior quality synthetic leather. Stepwise process used for leather manufacturing is given below:
Method of preparation
The present invention uses roadside fallen leaves or agro- waste such as sugarcane bagasse or paddy straw, in powder form as a reinforcement material for the production of biodegradable synthetic leather (Adopted Trade Name ‘Flora’) using wet coagulation and transfer coating process. This processing method used to produce plant-based biodegradable synthetic leather (Flora) involves the following steps:
Procurement of base material
Natural fabric (such as hemp/cotton/ viscose) and polyester fabric were used as a base material for the preparation of synthetic leather as these are usually porous. Hemp/cotton/ viscose fiber is considered one of the highly dominant classes of bast natural fibers, which obtained from the hemp plant with the species of Cannabis. Nowadays, hemp/cotton/ viscose fibers have received wide acceptance as natural fibers along with inherent mechanical, thermal, and acoustic properties to make them beneficial for reinforcements in a polymer fabric composite. Hemp/cotton/ viscose fibers is nearly 100% biodegradability in normal environmental conditions. The hemp fabric is obtained from Shubhshiv Corporation, Gurugram, India. Polyester Cotton fabric is obtained from Mahavir Tex Syn Pvt Ltd Faridabad, Haryana-121006, India. Viscose fabric is purchased by the Naakubetta Textile Company, Vellakinar, Coimbatore, Tamil Nadu, India
Formulation of coating on fabric
For preparation of coating on fabric, polyurethane is used as a matrix material; fine grade natural leaf powder (1-50µm) of fallen leaves of any plant or fine grade powder (1-50µm) of agro- waste such as sugarcane bagasse or paddy straw, is used as reinforcement material. Dimethyl formamide (DMF) is used for coagulaton process and organic pigments are used.
Polyurethane (PU resin), natural leaf powder or powder of agri- waste such as sugarcane bagasse or paddy straw (1-20wt.%) and methyl ethyl ketone (MEK) (50wt.%) and other organic compounds such as organic pigments (10-15wt %), and lacquer as per requirement were mixed together for 15 minutes with specially designed three blade stirrer. The stirrer is designed to generate multiple small sized vortices. Further a levelling agent i.e., natural leaf powder is again added to vortex and mixed properly with help of said stirrer for 8 minutes. Once everything is in the mixed solution, it is placed under vacuum at 600 psi for 45 minutes to release air from the prepared mixed solution and mixed solution is ready for coating.

Coating of solution on hemp/cotton/ viscose and polyester fabric (Pre dip step)
The prepared solution comprising polyurethane resin, DMF and natural leaf powder or agro- waste such as sugarcane bagasse and paddy straw is further coated over the base layer, which is basically the hemp/cotton/ viscose fabric. This leads to the preparation of partial synthetic leather.

Partial coagulation step
In partial coagulation step, hemp/cotton/ viscose and polyester fabric is passed into pre coagulation tank containing chemicals such as DMF and softener water (composition ratio = 15:85). In pre coagulation tank, hemp/cotton/ viscose and polyester fabric undergoes certain chemical reactions with the DMF and soft water to form cells in the hemp fabric and this leads to conversion of hemp/cotton/ viscose and polyester fabric into partially coagulated hemp fabric.

Squeezing and Semi-dry heating
In the squeezing step, partially coagulated hemp/cotton/ viscose and polyester fabric is passed into the squeezing rolls and after squeezing it is passed through semi-dry heating rolls for partial heating of the synthetic leather.

Coating process to fully coagulation
In this step, the partially coagulated hemp fabric is passed to another coagulation tank containing chemicals such as DMF and softener water (composition ratio = 20:80). In this tank, polymer coated fabric undergo certain chemical reactions to form cells in the partially coagulated hemp/cotton/ viscose and polyester fabric and this leads to conversion of partially coagulated hemp/cotton/ viscose and polyester fabric into fully coagulated hemp/cotton/ viscose and polyester fabric.

Washing step of fully coagulated hemp/cotton/ viscose and polyester fabric
Washing is carried out in four columns; the first three columns comprise of different concentrations of R/O water and different DMF: Softener water ratio. The first column comprises of 15:85 DMF: Softener water ratio, 2nd column comprises of 20:80 whereas the third column comprises of 10:90 DMF: Softener water ratio. The last column comprises of hot R/O water and only softener water and does not comprise of DMF for washing.

Heating step
After washing in four columns, the fully coagulated hemp fabric passes in the heating drum at 140oC by accumulator for partial drying of the product and for the purpose of complete drying the material further passes stenter oven at 170oC.
Cooling step
The cooling of the fully coagulated hemp fabric is conducted by passing the prepared leather through a series of four cooling drums and further the cooled product undergoes winding for preparation of batch rolls.

Transfer Coating process
The transfer coating process is applicable to produce synthetic leather (Flora). The texture and design surface on a fully coagulated leather requires a transfer coating process. The main uses of this type of coating technique are the transfer coated polyurethane fabrics is in up-market and the waterproof protective clothing. In the PU transfer coating process, the coating is done by blade or roller on one side of release paper to form a film, and then laminate this film into the fabric. The process is divided into a few steps;
? PU resin coat (which will become the top layer) onto the transfer paper and this transfer paper with the coating is passed into the heated chamber (165 oC) which is of 5 meters length. In the heated chamber, the coating is solidified into continuous film.
? Adhesive PU resin coat on the top layer, which will become the base layer (and is the adhesive that joins the top layer to the fabric). This base layer is passed into the heated chamber (which is of 5 meters length) to make it semi-solid. Fully coagulated leather fabric is glued on top of the semi coating and passed into a 15 meters lengthy heated chamber to improve the bonding strength between them.
? Peel off the coated fabric from the release paper.
After two coating process, the finished product is separated from the substrate (release paper), the release paper is further winded into batch rolls which can be reused. Finally, the final product is cooled down with the help of three cooling drums and winded on batch rolls for final physical inspection.
Experimental analysis of present invention (Flora)
Three samples were developed using the process as stated above. One sample used fallen leaves, the other used sugarcane bagasse and third used paddy straw as reinforced material.
The representative morphological features of present invention (Flora) samples developed are as displayed in Fig. 3. Paddy straw particles/ sugarcane bagasse/ natural fallen leaves were taken as reinforcement material.
Figure 3(a) presents topside morphological images of present invention (Flora) and the uniformed paddy straw particles reinforced in flora matrix. The interface bonding between paddy straw particles and flora matrix is strong which has positive influence on the physical and surface properties of the flora.
Figure 3(b) presents backside morphological images of flora fabric and strong interface bonding between adhesive materials and fabric is shown.
Similar behavior is shown in Fig. 3(c) and (d).
Particulate distribution in high quantity amounts to agglomeration of tree leaf particles as indicated in Fig. 3c. These points of agglomeration serve as the stress concentration points eventually amounting to the lowering of strength as observed under tensile strength.
Adhesive overlap within the matrix of fibers was observed in Figure 3d.
Coalesce of fibers and particulates (Fig. 3(e) and (f)) indicates even stress distribution among particulates, fibers and matrix enhancing strength.
Consequence of this was reflected in the increase in tensile and flexural strength, moduli of elasticity and rupture, impact strength, and tear strength. The proximity of these particles due to short interparticle distances of sugarcane bagasse's particle allows the transfer of heat when thermally excited. However, with the lower conductivity of the sugarcane bagasse's particle, the conductivity reduced with increasing the amount of sugarcane bagasse's particle in the flora matrix. At the same time, the load transfer rate properties of the flora from the particles to the flora matrix to the fabric fiber are enhanced which is shown in Fig 2(a). Failure analysis of Flora after tear strength test is shown in SEM-EDS image of chemical analysis of tree leaf reinforced Flora and SEM-EDS image of chemical analysis of sugarcane bagasse reinforced Flora have been shown in Fig 2(b) and (c), respectively.

Physical characterization of the leather of the present invention:
Physical characterization of the finished product was conducted in order to determine the thickness, tensile strength, tear strength, water vapor permeability, and water vapor absorption and flex resistance. Table 1 discloses the physical properties of leather prepared in present invention and named as FLORA and also comparative analysis of FLORA with natural leather and other synthetic leathers such as MUSKIN, DESSERTO, APPLESKIN, VEGA, PINATEX etc., which are available in market.
Table 1: Physical properties of present invention (FLORA) leather and comparative analysis of same with other existing leather material

Physical Properties Non-Woven Fabric: Flora Pinatex® PUR coat text PPK140 Fabric: Flora Faux Leather-2 Faux leather-3 Vegea®
Thickness ISO
17186-A(mm) 1.2- 1.4 1.43 1.37 1.0 0.95 0.90 0.95
Tensile Strength ISO 3376(N/mm2) 14.75- 16 4.5 10.2 12.56 12.83 10.09 9.4
Tear strength.
ISO 3377-1
(N/mm) 46.2- 50 31 17 26.46 - - 16.6
Flex Res
ISO 32100
Flex Cycles to Grade = 2 >200000 upto 300000 150000 200000 >200000 - - 500000
Peel Strength
(N/mm) 3.7 – 4.5 - - 2.18 - - -
Hydrolysis
(Hours) 21-22 - - 20 - - -
Fabric (gsm) 220 - - 110 - - -
GSM of Total Product 480 - - 495 - - -
Elongation (%) 130 - - 100 41.15 56.3 -

The above table shows the physical properties of FLORA leather, which is produced in the present invention. It is observed that the tensile strength of flora in wrap direction is 14.75 to 16 (N/mm2) which is higher as compared to Coated textile, Muskin® and Pinatex leather. Several factors such as wrap or weft direction, influence of stich yarn, regularity of yarn tension, during knitting, quality of coated fabric, structural uniformity of yarn density, etc. influence the tensile strength are evaluated. The tensile properties of the coated biaxial fabric mainly depend on the insertion yarns. The linear density of the stitch yarn and the density of insertion yarns are different in the warp and weft directions.
The higher linear density of the insertion yarns in the warp direction leads to a higher tensile strength in this direction.

The tensile strength in the warp-wise direction of FLORA is 14.75 to 16 (N/mm2) higher than the Muskin® and Kombucha (naturally grown material), PUR coat text, Appleskin®, Vegea® (Coated textile) and SnapPap® (non-woven of plant fiber). Tearing strength of the coated fabric depends on the coating thickness, bonding between the fabric and coated materials, and chemical composition of the coated materials and other factors such as by reducing the thread count in the direction opposite to the direction of test, the tearing strength can be increased.
Present invention is novel in terms of prior art as none of the prior art studies discloses the use of bio-waste of fallen leaf powder in manufacturing of synthetic leather to enhance the biodegradability of the synthetic leather.

Inventive step by way of technological advancement lies in utilization of plant bio-waste including fallen leaves of any tree, sugarcane bagasse and paddy straw which otherwise contributes to environmental pollution in synthesis of synthetic leather in order to enhance its biodegradability. Moreover, the synthetic leather disclosed in present invention utilizes less amount of chemical, possesses biodegradability and utilizes plant bio-waste, hence also possesses economic advancement over prior art studies.
The present invention is of great industrial application as it will boost up the leather industry, fashion industry, textile industry, automobile industry, furniture industry for preparation of footwear, jackets, gloves, car seat covers, sofa covers, wallets etc.

CLAIMS:WE CLAIM:

1. Plant bio-waste based synthetic biodegradable polyurethane leather WHEREIN the same consists of hemp/cotton/viscose) and polyester fabric as a base material, Polyurethane (PU resin), natural leaf powder or powder of agro-waste (1-20wt.%) as natural reinforcement material and DMF (10wt.%) along with organic pigments (10-15wt. %) and lacquer.

2. The polyurethane leather as claimed in claim 1 WHEREIN the natural leaf powder is prepared by drying and grinding fallen leaves of any tree or plant to a particle size of (1-50µm).

3. The polyurethane leather as claimed in claim 1 WHEREIN powder of agro- waste is prepared by drying and grinding sugarcane bagasse or paddy straw to a particle size of (1-50µm).

4. The polyurethane leather as claimed in claim 1 WHEREIN the same has following characteristic features at a GSM of 480 of the finished product:
- Thickness (mm): 1.2- 1.4
- Tensile Strength: 14.75- 16
- Tear Strength (N/mm2): 46.2- 50
- Flex Res (Flex Cycles to Grade = 2): >200000 up to 300000
- Peel strength (N/mm): 3.7-4.5
- Hydrolysis (Hours): 21-22

5. The method of preparation of the polyurethane leather as claimed in claim 1 WHEREIN the same consists of following steps:
Step a) Polyurethane (PU resin), natural leaf powder or powder of agro- waste such as sugarcane bagasse or paddy straw (1-20wt.%) and DMF (10wt.%) and other organic compounds such as organic pigments (10-15wt %), and lacquer are mixed together for 15 minutes with specially designed three blade stirrer which generates multiple small sized vortices;
Step b) natural leaf powder is again added to vortex as a levelling agent and mixed properly with help of said stirrer for 8 minutes;

Step c) once everything is in the mixed solution, it is placed under vacuum at 600 psi for 45 minutes to release air from the prepared mixed solution and mixed solution is ready for coating;

Step d) solution obtained in step c) is coated over the base layer of hemp/cotton/ viscose and polyester fabric leading to partial synthetic leather;

Step e) the hemp/cotton/ viscose and polyester fabric is passed into pre coagulation tank containing chemicals such as DMF and softener water (composition ratio = 15:85) leading to conversion of hemp/cotton/ viscose and polyester fabric into partially coagulated hemp/cotton/ viscose and polyester fabric;

Step f) the partially coagulated hemp/cotton/ viscose and polyester fabric is passed into the squeezing rolls followed by passing it through semi-dry heating rolls for partial heating of the synthetic leather;

Step g) the partially coagulated hemp/cotton/ viscose and polyester fabric obtained in step f) is passed to another coagulation tank containing chemicals such as DMF and softener water (composition ratio = 20:80) leading to conversion of partially coagulated hemp/cotton/ viscose and polyester fabric into fully coagulated hemp/cotton/ viscose and polyester fabric;

Step h) washing of fully coagulated hemp/cotton/ viscose and polyester fabric obtained in Step g) is carried out in four columns;

Step i) after washing, the fully coagulated and washed hemp/cotton/ viscose and polyester fabric (prepared leather) passes in the heating drum at 140oC by accumulator for partial drying of the product followed by drying the material in stenter oven at 170oC for fully drying;

Step j) the fully coagulated hemp/cotton/ viscose and polyester fabric is cooled by passing the prepared leather through a series of four cooling drums and followed by winding for preparation of batch rolls;

Step k) to provide texture and design surface on a fully coagulated leather, transfer coating process is carried out.

6. The method of preparation of the polyurethane leather as claimed in claim 1 WHEREIN the columns in washing carried out in step h) consists of first column comprising of 15:85 DMF: Softener water ratio, 2nd column comprising of 20:80, the third column comprising of 10:90 DMF: Softener water ratio and last column comprising of hot R/O water and only softener water.

7. The method of preparation of the polyurethane leather as claimed in claim 1 WHEREIN the transfer coating process of step k) consists of following steps:
- PU resin coat (which will become the top layer) onto the transfer paper and this transfer paper with the coating is passed into the heated chamber (165 oC) of 5 meters length where the coating is solidified into continuous film;
- adhesive PU resin coat on the top layer makes the base layer (and is the adhesive that joins the top layer to the fabric) which is passed into the heated chamber to make it semi-solid;

- fully coagulated leather fabric is glued on top of the semi-solid coating and passed into a 15 meters lengthy heated chamber to improve the bonding strength between them;

- peel off the coated fabric from the release paper;

- after two coating process, the finished product is separated from the substrate (release paper) and the release paper is winded into batch rolls which can be reused;

- the final product is cooled down with the help of three cooling drums and winded on batch rolls for final physical inspection.