Description:TECHNICAL FIELD
[0001] The present disclosure relates generally to the field of thermo-oxidative stabilization of polyolefins. More particularly, the present disclosure provides bio-based primary antioxidants for thermal oxidative stabilization of polyolefins and a process for preparation thereof.

BACKGROUND
[0002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
[0003] Polyolefins normally undergo high temperature manufacturing and fabrication operations and are susceptible to oxidation during various stages of their lifecycle. Antioxidants are used to inhibit the oxidative damage that is ultimately responsible for loss of physical properties, embrittlement and premature failure. The effectiveness of thermal stabilizers or antioxidants in stabilizing polymers depends on many factors including solubility, dispersion, ability to stabilize different polymer matrices, evaporation or volatilization during processing, conditions of use, and recycling.
[0004] Conventionally, various types of primary antioxidants, mostly hindered phenol based antioxidants, have been used to serve this purpose. For example, commercial antioxidant Pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamate) is based on the family of hindered phenols like 4-substituted-2,6-ditertiary butyl phenols. Notably, most of the conventional primary antioxidants are derived from synthetic organic molecules. However, stabilization of polyolefins with synthetic antioxidants can be used only upto a certain concentration, beyond which, if used, they make the polyolefins unfit for food contact applications. Typical hindered phenols tend to migrate to the surfaces of polymeric articles. Plastics that are used for food packaging have come under scrutiny because synthetic antioxidants may contaminate food and serve as a source of unknown cytotoxicity. Few details are known about the toxicity and migration of the transformation products of such antioxidants produced during processing and application. Other environmental concerns arise from the presence of trace levels of heavy metal catalyst used for antioxidant synthesis.
[0005] The aforesaid shortcomings as well as economic and environmental factors have led to growing interest in using greener, sustainable materials in place of synthetic counterparts as feedstocks. Such sustainable molecules provide the benefits of biodegradability, reduce wear to processing equipment, and low cost. In light of these benefits as well as concerns over the use of synthetic antioxidants, numerous bio-based phenols such as caffeic acid, ascorbic acid (vitamin C), C-tocopherol (vitamin E), curcumin, quercetin, and B-carotenes have reportedly been incorporated into different packaging materials as thermal stabilizers. For example, Al-Malaika et al. (Polymer Degradation and Stability 73 (2001) 491–503) examined the efficacy of the commercially-available compound vitamin E as a melt stabilizer for low density polyethylene (LDPE); Tatraalai et al. (European Polymer Journal 49 (2013) 1196-1203) similarly investigated the effect of curcumin, found in turmeric and other roots, on the processing stability of PE, wherein using various characterization techniques, they demonstrated that PE with 0.1 wt % curcumin showed superior thermo-oxidative stability compared to that for PE with 0.1 wt % Pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamate); Cerruti et al. (US Pub. No.: US20170058108A1) used ball milling and solvent extraction to obtain antioxidant fractions from grape seeds and tomato skins, incorporation of such carotenoid antioxidant fractions were reported to have positive effects on PP thermal stability; Maraveas et al. (Polymers 2021, 13(15), 2465; available at https://doi.org/10.3390/polym13152465) briefly described various naturally occurring small molecule or polymers such as lignin, and graft polymers, dopamine, and polydopamine, inulin, quercetin, limonene, and vitamins and their potential application for stabilization of polymers.
[0006] Despite rigorous research done in the technical field of thermo-oxidative stabilization of polyolefins, the conventional anti-oxidants, specifically, the primary anti-oxidants, suffer from one or more shortcomings. Consequently, there is a persistent need in the state of the art for bio-based primary antioxidants for thermal oxidative stabilization of polyolefins. Need is also felt of a process for preparation of bio-based primary antioxidants.
[0007] Each of the documents referred in the background section are incorporated herein, in its entirety, by way of reference. Further, none of the abovementioned documents are to be construed as relevant prior-art for the invention as embodied in the present disclosure. The sole intention of referring to and providing the abovementioned documents is to highlight some of the work already done in the technical field of thermo-oxidative stabilization of polyolefins.

OBJECTS OF THE INVENTION
[0008] An object of the present disclosure is to provide bio-based primary antioxidants for thermo-oxidative stabilization of polyolefins that alleviates one or more shortcomings associated with the conventional antioxidants.
[0009] Another object of the present disclosure is to provide bio-based primary antioxidants that show high thermal stability.
[0010] Another object of the present disclosure is to provide a process for preparation of bio-based primary antioxidants for thermo-oxidative stabilization of polyolefins.
[0011] Further object of the present disclosure is to provide a process for preparation of bio-based primary antioxidants that is economical.
[0012] Still further object of the present disclosure is to provide a process for preparation of bio-based primary antioxidants that is technically and commercially feasible.
[0013] Other objects of the present invention will be apparent from the description of the invention herein below.

SUMMARY
[0014] The present disclosure relates generally to the field of thermo-oxidative stabilization of polyolefins. More particularly, the present disclosure provides bio-based primary antioxidants for thermal oxidative stabilization of polyolefins and a process for preparation thereof.
[0015] An aspect of the present disclosure provides a compound of Formula I,

Formula I
wherein R1 is selected from H and substituted or unsubstituted, linear or branched C1 to C8 alkyl; and R2 is selected from H and substituted or unsubstituted, linear or branched C1 to C8 alkyl.
[0016] In some embodiments, the compound of Formula I is a compound of Formula II

Formula II
wherein R1 is selected from H and substituted or unsubstituted, linear or branched C1 to C8 alkyl; and R2 is selected from H and substituted or unsubstituted, linear or branched C1 to C8 alkyl.
[0017] In some embodiments, the compound of Formula I is a compound of Formula III

Formula III
wherein R1 is selected from H and substituted or unsubstituted, linear or branched C1 to C8 alkyl; and R2 is selected from H and substituted or unsubstituted, linear or branched C1 to C8 alkyl.
[0018] In some embodiments, R1 and R2 are same and are selected from substituted or unsubstituted, linear or branched C3 to C5 alkyl.
[0019] In some embodiments, the compound of Formula I is 3-(3,5-Di-tert-butyl-4-hydroxy-phenyl)-propionic acid 6-[3-(3,5-di-tert-butyl-4-hydroxy-phenyl)-propionyloxy]-hexahydro-furo[3,2-b]furan-3-yl ester represented by the following structure:
.
[0020] The primary anti-oxidants realized in accordance with embodiments of the present disclosure, when used/added in ppm levels during the melt processing of polyethylene, polypropylene and homo-polymers and copolymers thereof, impart excellent thermo-oxidative stabilization for various grades having the melt flow rate (MFR) ranging from 0.5 to 400 g/10 min. The primary anti-oxidants, and particularly, the compound - 3-(3,5-Di-tert-butyl-4-hydroxy-phenyl)-propionic acid 6-[3-(3,5-di-tert-butyl-4-hydroxy-phenyl)-propionyloxy]-hexahydro-furo[3,2-b]furan-3-yl ester, may be used in the concentration range of 100 to 5000 ppm, preferably, 100-3000 ppm, and more preferably 250-2000 ppm for thermo-oxidative stabilization of polyolefins.
[0021] Another aspect of the present disclosure relates to a process for preparation of a compound of Formula I,

Formula I
wherein R1 is selected from H and substituted or unsubstituted, linear or branched C1 to C8 alkyl; and R2 is selected from H and substituted or unsubstituted, linear or branched C1 to C8 alkyl,
the process comprising the steps of:
(a) contacting a premixture comprising a compound of Formula IV with a coupling agent and a base to obtain a reaction mixture; and
(b) mixing a compound of Formula V with the reaction mixture to obtain the compound of Formula I,

Formula IV Formula V
wherein, in Formula IV and Formula V, R1 and R2 are as defined above, and R is selected from H and substituted or unsubstituted, linear or branched C1 to C6 alkyl.
[0022] In some embodiments, the compound of Formula V is (3R,3aR,6S,6aR)-hexahydrofuro[3,2-b]furan-3,6-diol. In some embodiments, R1 and R2 are same and are selected from substituted or unsubstituted, linear or branched C3 to C5 alkyl. In some embodiments, the compound of Formula IV is Methyl 3-(3,5-Di-tert-butyl-4-hydroxyphenyl)propionate. In some embodiments, the coupling agent is selected from N,N'-dicyclohexane carbodiimide, 1-Ethyl-3-(3-dimethyl aminopropyl)carbodiimide, N,N,N′,N′-Tetramethyl-O-(1H-benzotriazol-1-yl)uronium hexafluoro phosphate, (1-Cyano-2-ethoxy-2-oxoethyliden aminooxy)dimethylamino-morpholino-carbenium hexafluorophosphate, 2-(1H-Benzotriazole-1-yl)-1,1,3,3-tetramethylaminium tetrafluoroborate and mixtures thereof. In some embodiments, the base is selected from pyridine, dimethyl amino pyridine, diethyl amine, triethyl amine, metal alkoxide, metal carbonate, metal amide and mixtures thereof.
[0023] In some embodiments, the step of obtaining the reaction mixture comprises the following sub-steps: (a1) dissolving the compound of Formula IV in a solvent to obtain the premixture, (a2) mixing the coupling agent and the solvent to the premixture to obtain the reaction mixture, and (a3) cooling the reaction mixture to a temperature ranging between 2°C to 20°C for a duration ranging between 0.1 hour to 2 hours. In some embodiments, the step (b) is carried out at a temperature ranging between 2°C to 15°C for a duration ranging between 0.1 hour to 2 hours.
[0024] Further aspect of the present disclosure is drawn towards use of a compound of Formula I for thermo-oxidative stabilization of polyolefins

Formula I
wherein R1 is selected from H and substituted or unsubstituted, linear or branched C1 to C8 alkyl; and R2 is selected from H and substituted or unsubstituted, linear or branched C1 to C8 alkyl.
[0025] Still further aspect of the present disclosure provides a composition for thermo-oxidative stabilization of polyolefins, said composition comprising: (a) a compound of Formula I, (b) a secondary anti-oxidant, and (c) an acid scavenger

Formula I
wherein R1 is selected from H and substituted or unsubstituted, linear or branched C1 to C8 alkyl; and R2 is selected from H and substituted or unsubstituted, linear or branched C1 to C8 alkyl.
[0026] In some embodiments, the composition comprises the compound of Formula I and the secondary anti-oxidant in a weight ratio ranging from 10:1 to 1:10. In some embodiments, the secondary anti-oxidant is selected from phosphanite based secondary antioxidant and phosphite based secondary antioxidant. In some embodiments, the weight ratio between the compound of Formula I and the acid scavenger ranges between 5.0:1.0 to 1.0:5.0. In some embodiments, the acid scavenger is selected from hydrotalcite type acid scavengers, metal stearates type acid scavengers and mixtures thereof.

BRIEF DESCRIPTION OF DRAWINGS
[0027] FIGs. 1-5 illustrate exemplary 1H NMR spectra, 13C NMR spectra, FT-IR spectrum, DSC curve and TGA curve of 3-(3,5-Di-tert-butyl-4-hydroxy-phenyl)-propionic acid 6-[3-(3,5-di-tert-butyl-4-hydroxy-phenyl)-propionyloxy]-hexahydro-furo[3,2-b]furan-3-yl ester respectively as a compound of Formula I, in accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION
[0028] The following is a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.
[0029] Each of the appended claims defines a separate invention, which for infringement purposes is recognized as including equivalents to the various elements or limitations specified in the claims. Depending on the context, all references below to the “invention” may in some cases refer to certain specific embodiments only. In other cases it will be recognized that references to the “invention” will refer to subject matter recited in one or more, but not necessarily all, of the claims.
[0030] As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
[0031] All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.
[0032] Various terms as used herein are shown below. To the extent a term used in a claim is not defined below, it should be given the broadest definition persons in the pertinent art have given that term as reflected in printed publications and issued patents at the time of filing.
[0033] The present disclosure relates generally to the field of thermo-oxidative stabilization of polyolefins. More particularly, the present disclosure provides bio-based primary antioxidants for thermal oxidative stabilization of polyolefins and a process for preparation thereof.
[0034] An aspect of the present disclosure provides a compound of Formula I,

Formula I
wherein R1 is selected from H and substituted or unsubstituted, linear or branched C1 to C8 alkyl; and R2 is selected from H and substituted or unsubstituted, linear or branched C1 to C8 alkyl.
[0035] In some embodiments, the compound of Formula I is a compound of Formula II

Formula II
wherein R1 is selected from H and substituted or unsubstituted, linear or branched C1 to C8 alkyl; and R2 is selected from H and substituted or unsubstituted, linear or branched C1 to C8 alkyl.
[0036] In some embodiments, the compound of Formula I is a compound of Formula III

Formula III
wherein R1 is selected from H and substituted or unsubstituted, linear or branched C1 to C8 alkyl; and R2 is selected from H and substituted or unsubstituted, linear or branched C1 to C8 alkyl.
[0037] In some embodiments, R1 and R2 are same and are selected from substituted or unsubstituted, linear or branched C3 to C5 alkyl. In some embodiments, both R1 and R2 is C4 alkyl or butyl.
[0038] In some embodiments, the compound of Formula I is 3-(3,5-Di-tert-butyl-4-hydroxy-phenyl)-propionic acid 6-[3-(3,5-di-tert-butyl-4-hydroxy-phenyl)-propionyloxy]-hexahydro-furo[3,2-b]furan-3-yl ester, represented by the following structure:
.
[0039] Another aspect of the present disclosure relates to a process for preparation of a compound of Formula I,

Formula I
wherein R1 is selected from H and substituted or unsubstituted, linear or branched C1 to C8 alkyl; and R2 is selected from H and substituted or unsubstituted, linear or branched C1 to C8 alkyl,
[0040] In some embodiments, the process includes the steps of:
(a) contacting a premixture comprising a compound of Formula IV with a coupling agent and a base to obtain a reaction mixture; and
(b) mixing a compound of Formula V with the reaction mixture to obtain the compound of Formula I,

Formula IV Formula V
wherein, in Formula IV and Formula V, R1 and R2 are as defined above, and R is selected from H and substituted or unsubstituted, linear or branched C1 to C6 alkyl.
[0041] In some embodiments, the compound of Formula V is (3R,3aR,6S,6aR)-hexahydrofuro[3,2-b]furan-3,6-diol (common name: Isosrbide). In some embodiments, R1 and R2 are same and are selected from substituted or unsubstituted, linear or branched C3 to C5 alkyl. In some embodiments, both R1 and R2 is C4 alkyl or butyl.
[0042] In some embodiments, the compound of Formula IV is Methyl 3-(3,5-Di-tert-butyl-4-hydroxyphenyl)propionate.
[0043] In some embodiments, the coupling agent is selected from N,N'-dicyclohexane carbodiimide, 1-Ethyl-3-(3-dimethyl aminopropyl)carbodiimide (EDC), N,N,N′,N′-Tetramethyl-O-(1H-benzotriazol-1-yl)uronium hexafluorophosphate (HATU), (1-Cyano-2-ethoxy-2-oxoethyliden aminooxy)dimethylamino-morpholino-carbenium hexafluorophosphate, 2-(1H-Benzotriazole-1-yl)-1,1,3,3-tetramethylaminium tetrafluoroborate and mixtures thereof.
[0044] In some embodiments, the base is selected from pyridine, dimethyl amino pyridine, diethyl amine, triethyl amine, metal alkoxide, metal carbonate, metal amide and mixtures thereof.
[0045] In some embodiments, metal alkoxide includes but not limited to sodium alkoxide, potassium alkoxide, aluminum alkoxide and magnesium alkoxide. However, any other metal alkoxide(s), as known to or appreciated by a person skilled in the art can be used to serve the intended purpose.
[0046] In some embodiments, metal carbonate includes but not limited to sodium carbonate, potassium carbonate, calcium carbonate and magnesium carbonate. However, any other metal carbonate(s), as known to or appreciated by a person skilled in the art can be used to serve the intended purpose.
[0047] In some embodiments, metal amide includes but not limited to lithium amide, sodium amide, and potassium amide. However, any other metal amide(s), as known to or appreciated by a person skilled in the art can be used to serve the intended purpose.
[0048] In some embodiments, the step of obtaining the reaction mixture comprises the following sub-steps: (a1) dissolving the compound of Formula IV in a solvent to obtain the premixture, (a2) mixing the coupling agent and the solvent to the premixture to obtain the reaction mixture, and (a3) cooling the reaction mixture to a temperature ranging between 2°C to 20°C for a duration ranging between 0.1 hour to 2 hours. In some embodiments, the reaction mixture is cooled to a temperature ranging between 2°C to 15°C, preferably, 5°C to 10°C for a duration ranging between 0.1 hour to 1 hour.
[0049] In some embodiments, the solvent is selected from a group consisting of: dichloromethane, dichloroethane, dimethylformamide, dimethylacetamide, acetone, methyl ethyl ketone, 2-Methyltetrahydrofuran (2-MeTHF), and Tetrahydrofuran. However, any other solvent(s), as known to or appreciated by a person skilled in the art can be used to serve the intended purpose.
[0050] In some embodiments, the step (b) is carried out at a temperature ranging between 2°C to 15°C for a duration ranging between 0.1 hour to 2 hours. In some embodiments, the step (b) is carried out at a temperature ranging between 5°C to 10°C for a duration ranging between 0.1 hour to 1 hour.
[0051] In one embodiment, the process described herein has the following temporal sequence of steps: (a1)  (a2)  (a3)  (b).
[0052] Further aspect of the present disclosure is drawn towards use of a compound of Formula I for thermo-oxidative stabilization of polyolefins

Formula I
wherein R1 is selected from H and substituted or unsubstituted, linear or branched C1 to C8 alkyl; and R2 is selected from H and substituted or unsubstituted, linear or branched C1 to C8 alkyl.
[0053] The embodiments pertaining to the compound of Formula I, as disclosed hereinabove, are applicable here as well.
[0054] Still further aspect of the present disclosure provides a composition for thermo-oxidative stabilization of polyolefins, said composition comprising: (a) a compound of Formula I, (b) a secondary anti-oxidant, and (c) an acid scavenger

Formula I
wherein R1 is selected from H and substituted or unsubstituted, linear or branched C1 to C8 alkyl; and R2 is selected from H and substituted or unsubstituted, linear or branched C1 to C8 alkyl.
[0055] The embodiments pertaining to the compound of Formula I, as disclosed hereinabove, are applicable here as well.
[0056] In some embodiments, the composition comprises the compound of Formula I and the secondary anti-oxidant in a weight ratio ranging from 10:1 to 1:10. In some embodiments, the weight ratio ranging from 8:1 to 1:10 or 5:1 to 1:8 or 5:1 to 1:5 or 3:1 to 1:4.
[0057] In some embodiments, the secondary anti-oxidant is selected from phosphanite based secondary antioxidant and phosphite based secondary antioxidant. In some embodiments, the phosphanite based antioxidant is Tetrakis(2,4-di-tert-butylphenyl)[1,1'-biphenyl]-4,4'-diylbisphosphonite. However, any other phosphanite(s), as known to or appreciated by a person skilled in the art can be used to serve the intended purpose. In some embodiments, the phosphite based antioxidant is selected from any or a combination of Tris(2,4-di-tert-butylphenyl) phosphite, 3,9-Bis(octadecyloxy)-2,4,8,10-tetraoxa-3,9diphosphaspiro[5.5]undecane, 3,9-Bis(2,6-di-tert-butyl-4-methylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane, 2,2'-Methylenebis(4,6-di-tert-butylphenyl) 2-ethylhexyl phosphite, Tris(nonylphenyl) phosphite, Tetra-C12-15-alkyl (propane-2,2-diylbis(4,1-phenylene)) bis(phosphite), 2-Ethylhexyl diphenyl phosphite, Triphenyl phosphite, and Triisodecylphosphite. However, any other phosphite(s), as known to or appreciated by a person skilled in the art can be used to serve the intended purpose.
[0058] In some embodiments, the weight ratio between the compound of Formula I and the acid scavenger is in the range of 5.0:1.0 to 1.0:5.0. In some embodiments, the weight ratio ranges between 4.0:1.0 to 1.0:4.0 or 3.0:1.0 to 1.0:4.0 or 3.0:1.0 to 1.0:3.0 or 2.0:1.0 to 1.0:3.0.
[0059] In some embodiments, the acid scavenger is selected from hydrotalcite type acid scavengers, metal stearates type acid scavengers and mixtures thereof. In some embodiments, hydrotalcite type acid scavengers includes but not limited to magnesium-aluminium oxide, magnesium-aluminum hydroxycarbonate. However, any other hydrotalcite(s), as known to or appreciated by a person skilled in the art can be used to serve the intended purpose. In some embodiments, metal stearates type acid scavengers include but not limited to, aluminum stearate, potassium stearate calcium stearate, magnesium stearate, barium stearate, copper stearate and zinc stearate. However, any other metal stearate(s), as known to or appreciated by a person skilled in the art can be used to serve the intended purpose.
[0060] While the foregoing describes various embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. The scope of the invention is determined by the claims that follow. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.
EXAMPLES
[0061] EXAMPLE 1 – Preparation of 3-(3,5-Di-tert-butyl-4-hydroxy-phenyl)-propionic acid 6-[3-(3,5-di-tert-butyl-4-hydroxy-phenyl)-propionyloxy]-hexahydro-furo[3,2-b]furan-3-yl ester
[0062] In a 3 neck 1000 mL round bottom flask, 3-(3,5-Di-tert-butyl-4-hydroxyphenyl)propionic acid (0.0371 mmol) was dissolved in dry dichloromethane (400 mL) at room temperature (~30°C) under nitrogen atmosphere. N, N’-dicyclohexylcarbodiimide (0.461 mmol) and 4-(Dimethylamino)pyridine (0.00923 mmol) were added into the reaction mixture under stirring condition. The resultant mixture was cooled to 5-10 ºC and maintained for 30 minutes. Isosorbide (0.184 mmol) was added to reaction mixture at the same temperature and stirred for 15 min at 5-10 ºC. Later, the temperature was slowly warmed up to room temperature (~30°C) and maintained for 12 hours under N2 atmosphere. After completion of the reaction, the reaction mixture was filtered to remove dicyclohexylurea (DCU). The solvent was evaporated under vacuum. The resultant yellow solid was recrystallized using diethyl ether and hexane to obtain a white solid with yield of about 90.5 %. Melting point was found to be 42 - 47 ºC. FIGs. 1-5 illustrate exemplary 1H NMR spectra, 13C NMR spectra, FT-IR spectrum, DSC curve and TGA curve of 3-(3,5-Di-tert-butyl-4-hydroxy-phenyl)-propionic acid 6-[3-(3,5-di-tert-butyl-4-hydroxy-phenyl)-propionyloxy]-hexahydro-furo[3,2-b]furan-3-yl ester, respectively.
[0063] EXAMPLE 2 - Preparation of 3-(3,5-Di-tert-butyl-4-hydroxy-phenyl)-propionic acid 6-[3-(3,5-di-tert-butyl-4-hydroxy-phenyl)-propionyloxy]-hexahydro-furo[3,2-b]furan-3-yl ester
[0064] In a 3 neck 1000 mL round bottom flask, 3-(3,5-Di-tert-butyl-4-hydroxyphenyl)propionic acid (0.0371 mmol) was dissolved in dry dichloromethane (400 mL) at room temperature (~30°C) under nitrogen atmosphere. EDC (0.461 mmol) and 4-(Dimethylamino)pyridine (0.00923 mmol) were added into reaction mixture under stirring condition. The resultant mixture was cooled to 5-10 ºC and maintained for 30 min. Isosorbide (0.184 mmol) was added to reaction mixture at the same temperature and stirred for 15 min at 5-10 ºC. Later, the temperature was slowly warmed up to room temperature (~30°C) and maintained for 24 hours under N2 atmosphere. The solvent was evaporated under vacuum. The resulted yellow solid was recrystallized using diethyl ether and hexane to obtain a white solid with a yield of about 92.1 %. Melting point was found to be 42 - 47 ºC.
[0065] EXAMPLE 3 - Preparation of 3-(3,5-Di-tert-butyl-4-hydroxy-phenyl)-propionic acid 6-[3-(3,5-di-tert-butyl-4-hydroxy-phenyl)-propionyloxy]-hexahydro-furo[3,2-b]furan-3-yl ester
[0066] In a 3 neck 1000 mL round bottom flask, 3-(3,5-Di-tert-butyl-4-hydroxyphenyl)propionic acid (0.0371 mmol) was dissolved in dry dichloromethane (400 mL) at room temperature (~30°C) under nitrogen atmosphere. HATU (0.461 mmol) and 4-(Dimethylamino)pyridine (0.00923 mmol) were added into reaction mixture under stirring condition. The resultant mixture was cooled to 5-10 ºC and maintained for 30 min. Isosorbide (0.184 mmol) was added to the reaction mixture at the same temperature and stirred for 15 min at 5-10 ºC. Later, the temperature was slowly warmed up to room temperature (~30°C) and maintained for 12 h under N2 atmosphere. The solvent was evaporated under vacuum. The resultant yellow solid was recrystallized using diethyl ether and hexane to obtain a white solid with a yield of about 87.5 g. Melting point was found to be 42 - 47 ºC.
[0067] STABILITY OF THE ANTI-OXIDANT AT ELEVATED TEMPERATURES
[0068] The stability of the anti-oxidant compound prepared in Example 1 above was investigated by thermogravimetric (TGA) analysis from a range of 20-600 ºC at a rate of 10 ºC/min. FIG. 5 illustrates an exemplary TGA curve of the compound. Usually, the polymer oxidative stability is a major concern during processing and application at higher temperatures. The thermal stability of the antioxidant is important at polymer process temperatures. 5 wt% and 50 wt % weight loss could be observed at 270 ºC and 381 ºC, respectively under N2 atmosphere, making it evident that the antioxidant compound is able to sustain higher temperatures.
[0069] EXAMPLE 4 – COMPOSITION FOR STABILIZATION OF POLYOLEFINS
[0070] 3-(3,5-Di-tert-butyl-4-hydroxy-phenyl)-propionic acid 6-[3-(3,5-di-tert-butyl-4-hydroxy-phenyl)-propionyloxy]-hexahydro-furo[3,2-b]furan-3-yl ester (code: “HP-AO”) as a primary anti-oxidant or reference/standard anti-oxidant (commercially available) - pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamate) (code: “Reference-AO”), a secondary antioxidant - Tris(2,4-di-tert-butylphenyl) phosphate (code: “Secondary-AO”), and an acid scavenger – DHT-4A® were added to polypropylene to prepare PP compositions. The PP compositions were prepared by mixing the polypropylene powder along with the HP-AO as a primary antioxidant, phosphite/phosphonite as a secondary antioxidant, and acid scavenger in requisite amounts in a high-speed mixer. Composition details are provided in Table 1 below:
Table 1: Polypropylene compositions
Sr. No. Sample Name HP-AO (ppm) Reference- AO (ppm) Secondary AO (ppm) DHT-4A® (ppm)
1. HP-AO 600 - 1200 500
2. Ref -01 - 600 1200 500

[0071] STUDIES TO ASSESS THERMO-OXIDATIVE STABILIZATION OF POLYPROPYLENE
[0072] The performance of the Polypropylene compositions (“HP-AO” and “Ref-01”) prepared in Example 4 above was evaluated using twin-screw extruder. Temperature profile maintained in the extruder (Omega 25, Screw dia.: 25 mm, L/D: 44) was from 150 to 250 °C and screw rotation was 50-150 rpm. Table 2 below provides temperature profile of Twin-Screw extruder during extrusion.
Table 2: Temperature profile of Twin-Screw extruder during extrusion
Barrel Temperature 150-250 ºC Out put 15 kg/hr
Die Temperature 200-210 ºC RPM 300
Melt Temperature 212-250 ºC - -

[0073] Five repetitive extrusions were done and coded as I pass, II pass, III pass, IV pass and V pass. After each extrusion, all the properties were measured such as melt flow index (MFI), yellowness index (YI), and thermal ageing. Thermal ageing was performed at 150 ºC in air circulated oven from 0 to 72 hours. After thermal aging, the mechanical properties and yellowness index were measured at each 24 hour time intervals.
[0074] In order to understand the melt flow rate (MFR) of PP compositions viz. Ref-1 and HP-AO, MFR for all five repetitive extrusions were determined keeping other parameters identical, results wherefor are provided in Table 3 below.
Table 3: MFR of PP compositions after each extrusion and difference of I and V pass
Sample Name Change in MFR (g/10 min) MFR Difference V and I pass
I Pass II Pass III Pass IV Pass V Pass
Ref-01 3.8 4.0 4.1 4.6 5.2 1.4
HP-AO 3.8 4.4 4.7 5.1 5.3 1.5

[0075] Notably, the MFR difference between I and V pass for both the cases was found to be almost same, which confirmed that the synthesized anti-oxidant has similar influence on overall MFR like that of the reference/standard anti-oxidant.
[0076] Yellowness index (YI) values of PP composites after each extrusion and its difference of I and V pass for both Ref-1 and HP-AO were determined using spectrophotometer, results wherefor are provided in Table 4 below.
Table 4: YI values of PP compositions after each extrusion and difference of I and V pass
Sample Name Change in Yellowness index with multiple pass YI Difference between V and I pass
I Pass II Pass III Pass IV Pass V Pass
Ref-01 5.9 9.4 12.8 14.6 15.6 9.6
HP-AO 5.7 9.9 12.9 14.1 15.7 10.0

[0077] The results revealed that YI difference between I and V pass for both Ref-1 and HP-AO is 9.6 and 10.0, respectively.
[0078] To check whether the YI changes after heat ageing treatment for different time intervals, both Ref-1 and HP-AO was heated at 150 oC for 24, 48, and 72 hours in air circulated oven. Surprisingly, after heat ageing, HP-AO showed lower YI difference as compared to Ref-01. Results for the change in Yellowness Index after thermal ageing in air circulated oven at 150 ºC are provided in Table 5 below.
Table 5: Change in Yellowness Index after thermal ageing in air circulated oven at 150 ºC
Sample Name Yellowness index Change in YI
Before ageing After 24 h After 48 h After 72 h (Before ageing - after 72 h)
Ref-01 5.9 11.7 19.0 23.6 17.7
HP-AO 5.7 10.3 17.9 23.2 17.5

[0079] Heat aged specimen of both Ref-1 and HP-AO were investigated for mechanical properties, results wherefor are provided in Table 6 below.

Table 6: Mechanical Analysis after heating at 150 C for 0 h and 72 h
Heat Aging Unit Ref-01 HP-AO

0 h Tensile Yield Strength MPa 34.3 35.1
Elongation at Yield % 9.6 9.9
Tensile Strength at Break MPa 21.8 21.9
Elongation at Break % 164 170

72 h Tensile Yield Strength MPa 33.8 34.8
Elongation at Yield % 6.7 7.1
Tensile Strength at Break MPa 34.7 35.0
Elongation at Break % 117 120

[0080] It could be noted that all the mechanical properties like tensile yield strength, elongation at yield, tensile strength at break, and elongation back for both Ref-1 and HP-AO are comparable even after 72 hours heat aging.
[0081] Although the subject matter has been described herein with reference to certain preferred embodiments thereof, other embodiments are possible. As such, the spirit and scope of the appended claims should not be limited to the description of the preferred embodiment contained therein. Furthermore, precise and systematic details on all above aspects are currently being made. Work is still underway on this invention. It will be obvious to those skilled in the art to make various changes, modifications and alterations to the invention described herein. To the extent that these various changes, modifications and alterations do not depart from the scope of the present invention, they are intended to be encompassed therein.

ADVANTAGES
[0082] The present disclosure provides bio-based primary antioxidants for thermo-oxidative stabilization of polyolefins that alleviates one or more shortcomings associated with the conventional antioxidants.
[0083] The present disclosure provides bio-based primary antioxidants that shows high thermal stability.
[0084] The present disclosure provides a process for preparation of bio-based primary antioxidants for thermo-oxidative stabilization of polyolefins that is economical.
[0085] The present disclosure provides a process for preparation of bio-based primary antioxidants for thermo-oxidative stabilization of polyolefins that is technically and commercially feasible.
, Claims:1. A compound of Formula I

Formula I
wherein R1 is selected from H and substituted or unsubstituted, linear or branched C1 to C8 alkyl; and R2 is selected from H and substituted or unsubstituted, linear or branched C1 to C8 alkyl.
2. The compound as claimed in claim 1, wherein the compound of Formula I is a compound of Formula II

Formula II
wherein R1 is selected from H and substituted or unsubstituted, linear or branched C1 to C8 alkyl; and R2 is selected from H and substituted or unsubstituted, linear or branched C1 to C8 alkyl.
3. The compound as claimed in claim 1, wherein the compound of Formula I is a compound of Formula III

Formula III
wherein R1 is selected from H and substituted or unsubstituted, linear or branched C1 to C8 alkyl; and R2 is selected from H and substituted or unsubstituted, linear or branched C1 to C8 alkyl.
4. The compound as claimed in one or more of claims 1 to 3, wherein R1 and R2 are same and are selected from substituted or unsubstituted, linear or branched C3 to C5 alkyl.
5. The compound as claimed in any of claims 1-3, wherein the compound of Formula I is 3-(3,5-Di-tert-butyl-4-hydroxy-phenyl)-propionic acid 6-[3-(3,5-di-tert-butyl-4-hydroxy-phenyl)-propionyloxy]-hexahydro-furo[3,2-b]furan-3-yl ester
.
6. A process for preparation of a compound of Formula I,

Formula I
wherein R1 is selected from H and substituted or unsubstituted, linear or branched C1 to C8 alkyl; and R2 is selected from H and substituted or unsubstituted, linear or branched C1 to C8 alkyl,
the process comprising the steps of:
(a) contacting a premixture comprising a compound of Formula IV with a coupling agent and a base to obtain a reaction mixture; and
(b) mixing a compound of Formula V with the reaction mixture to obtain the compound of Formula I,

Formula IV Formula V
wherein R1 and R2 are as defined above, and R is selected from H and substituted or unsubstituted, linear or branched C1 to C6 alkyl.
7. The process as claimed in claim 6, wherein the compound of Formula V is (3R,3aR,6S,6aR)-hexahydrofuro[3,2-b]furan-3,6-diol.
8. The process as claimed in claim 6 or 7, wherein R1 and R2 are same and are selected from substituted or unsubstituted, linear or branched C3 to C5 alkyl.
9. The process as claimed in one or more of claims 6 to 8, wherein the compound of Formula IV is Methyl 3-(3,5-Di-tert-butyl-4-hydroxyphenyl)propionate.
10. The process as claimed in one or more of claims 6 to 9, wherein the coupling agent is selected from N,N'-dicyclohexane carbodiimide, 1-Ethyl-3-(3-dimethyl aminopropyl)carbodiimide, N,N,N′,N′-Tetramethyl-O-(1H-benzotriazol-1-yl)uronium hexafluoro phosphate, (1-Cyano-2-ethoxy-2-oxoethyliden aminooxy)dimethylamino-morpholino-carbenium hexafluorophosphate, 2-(1H-Benzotriazole-1-yl)-1,1,3,3-tetramethylaminium tetrafluoroborate and mixtures thereof.
11. The process as claimed in one or more of claims 6 to 10, wherein the base is selected from pyridine, dimethyl amino pyridine, diethyl amine, triethyl amine, metal alkoxide, metal carbonate, metal amide and mixtures thereof.
12. The process as claimed in claims 6-11, wherein the step of obtaining the reaction mixture comprises the following sub-steps:
(a1) dissolving the compound of Formula IV in a solvent to obtain the premixture,
(a2) mixing the coupling agent and the solvent to the premixture to obtain the reaction mixture, and
(a3) cooling the reaction mixture to a temperature ranging between 2°C to 20°C for a duration ranging between 0.1 hour to 2 hours.
13. The process as claimed in claims 6-12, wherein the step (b) is carried out at a temperature ranging between 2°C to 15°C for a duration ranging between 0.1 hour to 2 hours.
14. Use of a compound of Formula I for thermo-oxidative stabilization of polyolefins

Formula I
wherein R1 is selected from H and substituted or unsubstituted, linear or branched C1 to C8 alkyl; and R2 is selected from H and substituted or unsubstituted, linear or branched C1 to C8 alkyl.
15. A composition for thermo-oxidative stabilization of polyolefins, said composition comprising:
(a) a compound of Formula I,

Formula I
wherein R1 is selected from H and substituted or unsubstituted, linear or branched C1 to C8 alkyl; and R2 is selected from H and substituted or unsubstituted, linear or branched C1 to C8 alkyl;
(b) a secondary anti-oxidant; and
(c) an acid scavenger.
16. The composition as claimed in claim 15, wherein the composition comprises the compound of Formula I and the secondary anti-oxidant in a weight ratio ranging from 10:1 to 1:10.
17. The composition as claimed in claim 15 or 16, wherein the secondary anti-oxidant is selected from phosphanite based secondary antioxidant and phosphite based secondary antioxidant.
18. The composition as claimed in one or more of claims 15 to 17, wherein the weight ratio between the compound of Formula I and the acid scavenger ranges between 5.0:1.0 to 1.0:5.0.
19. The composition as claimed in one or more of claims 15 to 18, wherein the acid scavenger is selected from hydrotalcite type acid scavengers, metal stearates type acid scavengers and mixtures thereof.