Description:FIELD
The present disclosure relates to a bimetallic catalyst system and a process for its preparation.
BACKGROUND
The background information herein below relates to the present disclosure but is not necessarily prior art.
Aliphatic polyesters and aromatic-aliphatic polyesters are the preferred choice of polymers to design a material with a balance of mechanical and biodegradable properties. These polymers can be produced by a right choice of monomers in a suitable proportion through a polycondensation process.
Conventionally, a distinct range of metals containing Lewis acid such as Titanium (Ti), Antimony (Sn), Magnesium (Mg), hafnium (Hf) bismuth (Bi) are used as catalyst during polycondensation.
Further, titanium and antimony-based catalyst expected to deliver higher efficiency among these catalytic systems. Antimony has certain limitation due to its toxicity. Titanium tetrabutoxide (TnBT) is a preferred catalyst system for synthesis of polyesters, particularly, biodegradable polyesters such as polybutylene adipate terephthalate (PBAT), polybutylene succinate (PBS), polybutyl acrylate (PBA), and the like due to its good hydrolytic stability. However, the catalysis of a polycondensation reaction have certain limitations such as longer reaction time, moisture sensitivity of catalyst, tendency to deteriorate, discoloration, and the like. Moreover, the catalyst system that provides a faster depletion of hydroxyl numbers in the reaction system resulting in shorter reaction time is desirable.
Therefore, there is, felt a need to provide a bimetallic catalyst system and a process for its preparation that mitigates the drawbacks mentioned herein above or at least provides a useful alternative.

OBJECTS
Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows:
It is an object of the present disclosure to ameliorate one or more problems given in the background or to at least provide a useful alternative.
An object of the present disclosure is to provide a bimetallic catalyst system.
Another object of the present disclosure is to provide a catalyst system for the polycondensation reaction.
Yet another object of the present disclosure is to provide a bimetallic catalyst system that leads to faster depletion of hydroxyl numbers of diol moieties in the reaction system.
Still another object of the present disclosure is to provide a simple, efficient and economic process for the preparation of a bimetallic catalyst system that is used in the preparation of aliphatic polymers.
Yet another object of the present disclosure is to provide a simple, efficient and economic process for the preparation of biodegradable polymers by using the bimetallic catalyst system.
Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure.
SUMMARY
The present disclosure relates to a bimetallic catalyst system, comprising an adduct of a titanium tratraalkoxide and a magnesium salt..
In accordance with the present disclosure, the titanium tetraalkoxide is selected from the group consisting of titanium tetraethoxide, titanium tetraisopropoxide, titanium tetramethoxide, titanium tetrabutoxide, and titanium tetraisobutoxide.
In accordance with the present disclosure, the magnesium salt is selected from the group consisting of magnesium dichloride and magnesium acetate.
In an embodiment of the present disclosure, a weight ratio of the magnesium salt to the titanium tetraalkoxide is in the range of 0.005:1 to 0.1:1.
The present disclosure further relates to a process for the preparation of a bimetallic catalyst system. The process comprises the step of mixing a magnesium salt and a titanium tetraalkoxide in a predetermined weight ratio to obtain a mixture. The mixture is heated to a first predetermined temperature for first predetermined time period to obtain a homogenous mixture. The homogenous mixture is cooled to a temperature in the range of 25 °C to 35 °C under an inert atmosphere to obtain the bimetallic catalyst system comprising an adduct of titanium tetraalkoxide and magnesium salt.
In accordance with the present disclosure, the magnesium salt is selected from the group consisting of magnesium dichloride and magnesium acetate.
In accordance with the present disclosure, the titanium tetraalkoxide is selected from the group consisting of titanium tetraethoxide, titanium tetra isopropoxide, titanium tetramethoxide, titanium tetrabutoxide, and titanium tetraisobutoxide.
In accordance with the present disclosure, the predetermined weight ratio of the magnesium salt to the titanium tetraalkoxide is in the range of 0.005:1 to 0.1:1.
In accordance with the present disclosure, the first predetermined temperature is in the range of 70 °C to 120 °C.
In accordance with the present disclosure, the first predetermined time period is in the range of 3 hours to 10 hours.
The present disclosure furthermore relates to a process for the preparation of a biodegradable polymer. The process comprises the step of mixing a bimetallic catalyst system, and monomers in a predetermined weight ratio at a temperature in the range of 25 °C to 35 °C under stirring to obtain a mixture. The mixture is heated under stirring at a second predetermined temperature for a second predetermined time period to obtain a product mixture. The product mixture is cooled to temperature in the range of 25 °C to 35 °C to obtain the biodegradable polymer.
In accordance with the present disclosure, the second predetermined temperature is in the range of 150 °C to 280 °C.
In accordance with the present disclosure, the second predetermined time period is in the range of 2 hours to 12 hours.
In accordance with the present disclosure, the monomer is selected from aliphatic acid and its ester derivatives, aromatic acid and its ester derivatives and diol compound.
In an embodiment of the present disclosure, a molar ratio of the aliphatic acid or its ester derivatives, to the aromatic acid or its ester derivatives, is in the range of 1:0.5 to 1:2.
In accordance with the present disclosure, the aliphatic acid is at least one selected from the group consisting of oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, brassylic acid, tetradecanedioic acid, 1,3-cyclopentanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, diglycolic acid, itaconic acid, maleic acid and fumaric acid.
In accordance with the present disclosure, the aliphatic acid ester derivative is at least one selected from the group consisting of methyl, ethyl, propyl and isopropyl ester derivatives of oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, brassylic acid, tetradecanedioic acid, 1,3-cyclopentanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, diglycolic acid, itaconic acid, maleic acid and fumaric acid.
In accordance with the present disclosure, the aromatic acid or its ester derivative is at least one selected from the group consisting of terephthalic acid, dimethyl terephthalate, phthalic acid, phthalic anhydride, isophthalic acid, dimethyl isophthalate, 4-methylphthalic acid, 4-methylphthalic anhydride, dimethyl phthalate, naphthalene dicarboxylic acid and diphenyl ether dicarboxylic acid.
In accordance with the present disclosure, the diol compound is at least one selected from the group consisting of ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2,4-dimethyl-2-ethyl-1,3-hexanediol, 2,2-dimethyl-1,3-propanediol, 2-ethyl-2-butyl-1,3-propanediol, 2-ethyl-2-isobutyl-1,3-propanediol and 2,2,4-trimethyl-1,6-hexanediol, 1,2-cyclopentanediol, 1,2-cyclohexanediol, 1,4-cyclohexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, and 1,4-cyclohexanedimethanol.
In accordance with the present disclosure, the biodegradable polymer is selected from the group consisting of polybutylene adipate terephthalate (PBAT), polybutylene succinate (PBS), poly(butylene adipate) (PBA), polybutylene succinate terephthalate (PBST).
The bimetallic catalyst system is used in an amount in the range of 0.5% to 2% with respect to the total weight of the monomers.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The present disclosure will now be described with the help of the accompanying drawing, in which:
Figure 1 illustrates 1H NMR of polybutylene adipate terephthalate PBAT prepared in accordance with the present disclosure;
Figure 2 illustrates a graphical representation for Hydroxy numbers using TnBT and TnBT.MgCl2 catalyst System with respect to time in accordance with the present disclosure;
Figure 3 illustrates a graphical representation for comparative reaction progress using TnBT and TnBT.MgCl2 with respect to time in accordance with the present disclosure; and
Figure 4 illustrates a graphical representation for percentage increase in progress of reaction using TnBT.MgCl2 with respect to time in accordance with the present disclosure.
DETAILED DESCRIPTION
The present disclosure relates to a bimetallic catalyst system and a process for its preparation.
Embodiments, of the present disclosure, will now be described with reference to the accompanying drawing.
Embodiments are provided so as to thoroughly and fully convey the scope of the present disclosure to the person skilled in the art. Numerous details are set forth, relating to specific components, and methods, to provide a complete understanding of embodiments of the present disclosure. It will be apparent to the person skilled in the art that the details provided in the embodiments should not be construed to limit the scope of the present disclosure. In some embodiments, well-known processes, well-known apparatus structures, and well-known techniques are not described in detail.
The terminology used, in the present disclosure, is only for the purpose of explaining a particular embodiment and such terminology shall not be considered to limit the scope of the present disclosure. As used in the present disclosure, the forms "a,” "an," and "the" may be intended to include the plural forms as well, unless the context clearly suggests otherwise. The terms "comprises," "comprising," “including,” and “having,” are open ended transitional phrases and therefore specify the presence of stated features, integers, steps, operations, elements, modules, units and/or components, but do not forbid the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The particular order of steps disclosed in the method and process of the present disclosure is not to be construed as necessarily requiring their performance as described or illustrated. It is also to be understood that additional or alternative steps may be employed.
The terms first, second, third, etc., should not be construed to limit the scope of the present disclosure as the aforementioned terms may be only used to distinguish one element, component, region, layer or section from another component, region, layer or section. Terms such as first, second, third etc., when used herein do not imply a specific sequence or order unless clearly suggested by the present disclosure.
Aliphatic polyesters and aromatic-aliphatic polyesters are the preferred choice of polymers to design a material with a balance of mechanical and biodegradable properties. These polymers can be produced by a right choice of monomers in a suitable proportion through a polycondensation process.
Conventionally a distinct range of metals containing Lewis acid such as Titanium (Ti), Antimony (Sn), Magnesium (Mg), hafnium (Hf) bismuth (Bi) are used as catalyst during polycondensation.
Further, titanium and antimony-based catalyst expected to deliver higher efficiency among these catalytic systems. Antimony has certain limitation due to its toxicity. Titanium tetrabutoxide (TnBT) is a preferred catalyst system for synthesis of polyesters, particularly, biodegradable polyesters such as polybutylene adipate terephthalate (PBAT), polybutylene succinate (PBS), poly(butyl acrylate) (PBA), and the like due to its good hydrolytic stability. However, the catalysis of a polycondensation reaction have certain limitations such as longer reaction time, moisture sensitivity of catalyst, tendency to deteriorate, discoloration, and the like. Moreover, the catalyst system that provides a faster depletion of hydroxyl numbers in the reaction system resulting in shorter reaction time is needed.
The present disclosure provides a bimetallic catalyst and a process for the preparation of bimetallic catalyst.
In one aspect, the present disclosure provides a bimetallic catalyst system. The bimetallic catalyst system comprises an adduct of a titanium tetraalkoxide and a magnesium salt.
In accordance with the present disclosure, the titanium tetraalkoxide is selected from the group consisting of titanium tetraethoxide, titanium tetraisopropoxide, titanium tetramethoxide, titanium tetrabutoxide, and titanium tetraisobutoxide. In an exemplary embodiment of the present disclosure, the titanium tetraalkoxide is titanium tetrabutoxide.
In accordance with the present disclosure, the magnesium salt is selected from the group consisting of magnesium dichloride and magnesium acetate. In an exemplary embodiment of the present disclosure, the magnesium salt is magnesium dichloride.
In an embodiment of the present disclosure, a weight ratio of the magnesium salt to the titanium tetraalkoxide is in the range of 0.005:1 to 0.1:1. In an exemplary embodiment of the present disclosure, the weight ratio of the magnesium salt to the titanium tetraalkoxide is 0.02:1.
In another aspect, the present disclosure provides a process for the preparation of a bimetallic catalyst system. The process comprises the following steps:
mixing a magnesium salt and a titanium tetraalkoxide in a predetermined weight ratio to obtain a mixture;
heating the mixture to a first predetermined temperature for a first predetermined time period to obtain a homogenous mixture; and
cooling the homogenous mixture to a temperature in the range of 25 °C to 35 °C under an inert atmosphere to obtain the bimetallic catalyst system comprising an adduct of titanium tetraalkoxide and magnesium salt.
The process is described in detail herein below.
In a first step, magnesium salt and titanium tetraalkoxide are mixed in a predetermined weight ratio to obtain a mixture.
In accordance with the present disclosure, the titanium tetra alkoxide is selected from the group consisting of titanium tetraethoxide, titanium tetra isopropoxide, titanium tetramethoxide, titanium tetrabutoxide, titanium tetra isobutoxide. In an exemplary embodiment of the present disclosure, the titanium tetra alkoxide is titanium tetrabutoxide.
In accordance with the present disclosure, the magnesium salt is selected from the group consisting of magnesium dichloride and magnesium acetate. In an exemplary embodiment of the present disclosure, the magnesium salt is magnesium dichloride.
In accordance with the present disclosure, the predetermined weight ratio of the magnesium salt to the titanium tetraalkoxide is in the range of 0.005:1 to 0.1:1. In an exemplary embodiment of the present disclosure, the predetermined weight ratio of magnesium dichloride to titanium tetrabutoxide is 0.02:1.
In a second step, the mixture is heated to a first predetermined temperature for first predetermined time period to obtain a homogenous mixture.
In accordance with the present disclosure, the first predetermined temperature is in the range of 70 °C to 120 °C. In an exemplary embodiment, the first predetermined temperature is 90 °C.
In accordance with the present disclosure, the first predetermined time period is in the range of 3 hours to 10 hours. In an exemplary embodiment, the first predetermined time period is 5 hours.
In a third step, the homogenous mixture is cooled to a temperature in the range of 25 °C to 35 °C under an inert atmosphere to obtain the bimetallic catalyst system comprising an adduct of titanium tetraalkoxide and magnesium salt.
In an exemplary embodiment, the homogenous mixture is cooled to 30 °C.
In an embodiment, the inert atmosphere is nitrogen atmosphere.
In still another aspect, the present disclosure provides a process for the preparation of a biodegradable polymer using a bimetallic catalyst system.
The process comprises the following steps:
mixing the bimetallic catalyst system of the present disclosure, and monomers in a predetermined weight ratio at a temperature in the range of 25 °C to 35 °C under stirring to obtain a mixture;
heating the mixture under stirring at a second predetermined temperature for a second predetermined time period to obtain a product mixture; and
cooling the product mixture to temperature in the range of 25 °C to 35 °C to obtain the biodegradable polymer.
In accordance with the present disclosure, the second predetermined temperature is in the range of 150 °C to 280 °C. In an exemplary embodiment, the second predetermined temperature is 200 °C.
In accordance with the present disclosure, the second predetermined time period is in the range of 2 hours to 12 hours. In an exemplary embodiment, the second predetermined time period is 6 hours.
In accordance with the present disclosure, the monomer is selected from aliphatic acid and its ester derivatives, aromatic acid and its ester derivatives and diol compound.
In an embodiment of the present disclosure, a molar ratio of the aliphatic acid or its ester derivatives to the aromatic acid or its ester derivatives is in the range of 1:0.5 to 1:2. In an exemplary embodiment of the present disclosure, the molar ratio of the aliphatic acid to the aromatic acid is 1:1.
In accordance with the present disclosure, the aliphatic acid is at least one selected from the group consisting of oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, brassylic acid, tetradecanedioic acid, 1,3-cyclopentanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, diglycolic acid, itaconic acid, maleic acid and fumaric acid.
In accordance with the present disclosure, the aliphatic acid ester derivative is at least one selected from the group consisting of methyl, ethyl, propyl and isopropyl ester derivatives of oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, brassylic acid, tetradecanedioic acid, 1,3-cyclopentanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, diglycolic acid, itaconic acid, maleic acid and fumaric acid. In an exemplary embodiment, the aliphatic acid ester derivative is dimethyl adipate (DMA).
In accordance with the present disclosure, the aromatic acid or its ester derivative is at least one selected from the group consisting of terephthalic acid, dimethyl terephthalate, phthalic acid, phthalic anhydride, isophthalic acid, dimethyl isophthalate, 4-methylphthalic acid, 4-methylphthalic anhydride, dimethyl phthalate, naphthalene dicarboxylic acid and diphenyl ether dicarboxylic acid. In an exemplary embodiment, the aromatic acid ester is dimethyl terephthalate (DMT).
In accordance with the present disclosure, the diol compound is at least one selected from the group consisting of ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2,4-dimethyl-2-ethyl-1,3-hexanediol, 2,2-dimethyl-1,3-propanediol, 2-ethyl-2-butyl-1,3-propanediol, 2-ethyl-2-isobutyl-1,3-propanediol and 2,2,4-trimethyl-1,6-hexanediol, 1,2-cyclopentanediol, 1,2-cyclohexanediol, 1,4-cyclohexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, and 1,4-cyclohexanedimethanol. In an exemplary embodiment, the aliphatic diol is 1,4 butanediol.
In an embodiment of the present disclosure, a bifunctional/multifunctional compound is added at the initial stage of polymerization.
The bifunctional/multifunctional compound is selected from the group consisting of glycerol, pentaerythritol, 1,1,1-trimethylolethane, 1,2,4-butanetriol, trimellitic acid, pyromellitic acid, trimethylolethane, polyethertriols, trimesic acid, pyromellitic acid and hydroxyisophthalic acid.
In another embodiment of the present disclosure, a bifunctional/multifunctional compound is added after polymerization.
The bifunctional/multifunctional compound is selected from the group consisting of diisocyanate compounds such as tolylene 2,4 diisocyanate, tolylene 2,6 diisocyanate, 2,2 diphynyl methane diisocyanate, hexamethyl 1,6 diisocyanate. Epoxy compounds such as 1,4-Butanediol diglycidyl ether, 1,2-Ethanediol diglycidyl ether.
Generally, the polyesters are linear polymers. The addition of bifunctional/multifunctional compounds in the polymerization reaction facilitates the polymer chain to have side branch that leads to an improved melt-strength in the polymer due to entanglement of the polymer chains.
In accordance with the present disclosure, the biodegradable polymer is selected from the group consisting of polybutylene adipate terephthalate (PBAT), polybutylene succinate (PBS), poly(butyl adipate) (PBA), polybutylene succinate terephthalate (PBST). In an exemplary embodiment, the biodegradable polymer is polybutylene adipate terephthalate (PBAT).
The bimetallic catalyst system is used in an amount in the range of 0.5% to 2% with respect to the total weight of the monomers. In an exemplary embodiment, the amount of the bimetallic catalyst system is 1.3% with respect to the total weight of the monomers.
The present disclosure provides a bimetallic catalyst which is an adduct of titanium tetraalkoxide and magnesium salt. The presence of magnesium moiety in the catalyst system has a positive effect to enhance the lewis acidity of titanium moiety.
The bimetallic catalyst of the present disclosure provides a faster depletion of hydroxyl numbers of diol moieties in the reaction system as compared to monometallic catalyst system. It effects an overall faster rate of reaction that can be monitored by measuring the depletion of monomer concentration with respect to time. This provides a robust catalyst system for the polymerization.
The bimetallic catalyst system and the process of the present disclosure can be easily adopted in the existing commercial aliphatic and aromatic-aliphatic polymers production, particularly, biodegradable polyesters such as polybutylene adipate terephthalate (PBAT), polybutylene succinate (PBS) and poly(butylene adipate) (PBA).
The foregoing description of the embodiments has been provided for purposes of illustration and not intended to limit the scope of the present disclosure. Individual components of a particular embodiment are generally not limited to that particular embodiment, but, are interchangeable. Such variations are not to be regarded as a departure from the present disclosure, and all such modifications are considered to be within the scope of the present disclosure.
The present disclosure is further described in light of the following experiments which are set forth for illustration purpose only and not to be construed for limiting the scope of the disclosure. The following experiments can be scaled up to industrial/commercial scale and the results obtained can be extrapolated to industrial scale.
Experimental details:
Experiment 1: Process for the preparation of the bimetallic catalyst (TnBT.MgCl2) system in accordance with the present disclosure
An experimental set up was used consisting of dried and nitrogen purged cylindrical glass reactor.
20.0 mg of anhydrous magnesium dichloride and 1000 mg of titanium tetrabutoxide were mixed in a cylindrical glass reactor to obtain a mixture. The mixture was heated to 90 °C and maintained for 5 hours to obtain a homogeneous mixture. The homogeneous mixture was cooled to 30 °C under inert atmosphere (nitrogen) to obtain the bimetallic catalyst system comprising an adduct of titanium tetrabutoxide and magnesium dichloride (TnBT.MgCl2).
Experiment 2: Process for the preparation of the polybutylene adipate terephthalate (PBAT)
Example A: Process for the preparation of the polybutylene adipate terephthalate (PBAT) by using the bimetallic catalyst system (TnBT:MgCl2) in accordance with the present disclosure.
An experimental set up was used consisting of cylindrical glass reactor fitted with a Dean Stark apparatus and a condenser along with nitrogen purging.
1.02 g of bimetallic catalyst (TnBT.MgCl2) obtained in Experiment 1, 25.61 g of dimethyl adipate (DMA), 28.55 g of dimethyl terephthalate (DMT), and 25.61 g of 1,4 butanediol (BDO) were mixed at 30 °C in a cylindrical glass reactor to obtain a mixture. The mixture was heated under stirring at 200 °C for 6 hours to obtain a product mixture. The obtained product mixture was cooled at 30 °C to obtain a polybutylene adipate terephthalate (PBAT).
Figure 1 illustrates 1H NMR of polybutylene adipate terephthalate (PBAT) in CDCl3.
Comparative Example B
Process for the preparation of the polybutylene adipate terephthalate (PBAT) (using monometallic TnBT as a catalyst)
An experimental set up was used consisting of cylindrical glass reactor fitted with a Dean Stark apparatus and a condenser along with nitrogen purging.
1 g of Titanium tetrabutoxide (TnBT), 25.61 g of dimethyl adipate (DMA), 28.55 g of dimethyl terephthalate (DMT), and 25.61 g butanediol (BDO) were mixed at 30 °C in a glass reactor to obtain a mixture. The mixture was heated under stirring at 200 °C for 6 hours to obtain a product mixture. The obtained product mixture was cooled at 30 °C to obtain a polybutylene adipate terephthalate (PBAT).
Experiment 3: Determination of hydroxyl value
Hydroxyl values (HV) were determined using a titration method.
While carrying out the above procedures according to Experiment 2 i.e. process for the preparation of the PBAT by using bimetallic catalyst (Example A) and monometallic catalyst (Comparative Example B) the samples were collected for Hydroxyl value determination every consecutive 2 hours (0 hour, 2 hours, 4 hours and 6 hours).
Sample preparation for hydroxyl value determination: The collected samples were dissolved in a 1:1 mixture of phthalic anhydride solution (25 ml) and toluene (25 ml) in 250 ml conical flask. The conical flask was numbered accordingly as sample no. 1, 2, 3 and 4.
Procedure: The conical flask was connected to a condenser and was heated to reflux at 115 °C for 2.5 hours to obtain a reaction mixture. The reaction mixture was cooled and 6 ml water was added to obtain a cooled reaction mixture. The cooled reaction mixture was heated to 115 °C and refluxed for 1.5 hour to obtain a heated reaction mixture. The heated reaction mixture was allowed to cool and was titrated with a 1 N NaOH solution and phenolphthalein indicator till the pink colour persist for at least 15 seconds.
The procedure was repeated for all the samples- sample no. 1, 2, 3 and 4.
The hydroxyl value (HV) is proportional to the carboxylic acid concentration present after reaction and is defined as milligrams of potassium hydroxide (KOH) required to neutralize one gram of sample.
The HV (in mg KOH/g) was calculated via the formula:

Hydroxyl Value (HV)=(B-A×56.1×N)/W

wherein:
A = NaOH solution required for titration of the sample, ml,
B = NaOH solution required for titration of the blank, ml,
N = normality of the NaOH solution, and
W = sample used, (g)
From Figure 2, it is clear that the use of TnBT.MgCl2 catalyst results in lesser hydroxyl values than TnBT catalyst.
The depletion of hydroxyl moiety in the reaction mixture with respect to time was measured through hydroxyl number determination method.
The progress of the esterification reaction was shown in terms of the depletion of one monomer i.e butanediol and the depletion of hydroxyl groups of butanediol was measured.
Table 1: the reaction progress of Example A in accordance with the present disclosure and comparative example B at consecutive 2 hours. (0 hr, 2 hours, 4 hours, 6 hours)
Sample No. Time
(Hours) TnBT.MgCl2 Hydroxyl value (mg KOH/g TnBT Hydroxyl value (mg KOH/g TnBT.MgCl2 % Depletion of hydroxyl number TnBT % Depletion of hydroxyl number Percentage (%) increase in progress of reaction in TnBT.MgCl2

1 0 1166 1166 0 0 0.00
2 2 487 505 58.23 56.69 1.54
3 4 156 200 86.62 82.85 3.77
4 6 110 164 90.57 85.93 4.63

The % increase in progress of reaction carried out using TnBT.MgCl2 and TnBT was calculated based on % depletion of hydroxyl number with respect to time, during the course of reaction.
p = No – N/No
P = extent of reaction or conversion to polymer
No = Total hydroxyl number at the start of reaction
N = Total hydroxy number at time t
For example, at time = 6 hour
No = 1166 (Calculated by Hydroxyl method that was given in main text)
N = 110 (Calculated by Hydroxyl method that was given in main text)
[ (1166-110)/1166 ] x 100
= 90.567
From Table 1 and Figure 3, it is clear that the rate of reaction is faster with the use of bimetallic TnBT.MgCl2 catalyst as compared to monometallic TnBT catalyst.
From Figure 4, it is clear that the use of TnBT.MgCl2 catalyst results in 4.63 % increase in rate of reaction as compared to TnBT catalyst.
Experiment 4: Determination of molecular weight
While carrying out the procedures according to Experiment 2 i.e. process for the preparation of the PBAT using bimetallic catalyst (Example A) and monometallic catalyst (Comparative Example B) the sample were collected at a predetermined time interval (i.e. 2 hours, 5 hours and 7 hours) for molecular weight determination.
Molecular weight was determined by Gel Permeation Chromatography (GPC) method.
GPC measurements were carried on a PL GPC 220 at 40 oC using (tetrahydrofuran) THF, as the mobile phase. The analysis were carried out at a flow rate of 1 mL/min using a set of three PL-gel (10u) Mixed-B column with a linear molecular weight operating range of 500-10,000,000g/mol (PS equiv) along with a guard column and a Refractive Index (RI) detector. Columns were calibrated with Polystyrene standards and the molecular weights reported are wrt to Polystyrene.
Table 2: GPC data for the analyzed examples
Sample No. Time (Hours) Mn (g/mol) Mw (g/mol) PDI (Mn/Mw) Mn (g/mol) Mw (g/mol) PDI (Mn/Mw)
Example Comparative Example
1 2 hours 869 1497 1.7 831 1322 1.6
2 5hours 1269 2285 1.8 999 1820 1.8
3 7 hours 1312 2335 1.7 1083 1923 1.8
Mn-Number average molecular weight
Mw-Weight average molecular weight
PDI-Polydispersity index (Mw/Mn)
The polydispersity index (PI) is a measure of the heterogeneity of a sample based on size.
The mechanical strength and properties of a biodegradable polymer depend on the molecular weight and polydispersity index of the polymer.
Polydispersity index = Mw/Mn
Polymers with low polydispersity indices (PDIs) have a relatively narrow distribution of molecular weights, meaning that the sizes of their polymer chains are more uniform. Such polymers are often desired in various applications because they offer more predictable and consistent properties.
From Table 2, it is depicted that the average polydispersity index of the polymer obtained by the experimental Example in accordance with the present disclosure is same as the average polydispersity index of the polymer obtained by comparative example. Therefore, the polymer obtained by condensation polymerization using bimetallic TnBT.MgCl2 catalyst and monometallic TnBT catalyst has similar polymeric properties i.e. narrow distribution of molecular weight, uniform sizes of polymer chains as desired for commercial application. However, the use of bimetallic TnBT.MgCl2 catalyst results in increase in rate of reaction and faster depletion of hydroxyl numbers of diol compound in the reaction system as compared to monometallic catalyst system i.e. TnBT catalyst.
TECHNICAL ADVANCEMENTS
The present disclosure described herein above has several technical advantages including, but not limited to, the realization of:
a bimetallic catalyst for the preparation of a biodegradable polymer that;
increases the rate of reaction; and
leads to faster depletion of hydroxyl numbers of diol compound in the reaction system; and
a process for the preparation of a bimetallic catalyst system that;
is simple, efficient and economic;
a process for the preparation of a biodegradable polymer that:
is simple, efficient and economic.
Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the invention to achieve one or more of the desired objects or results. While certain embodiments of the inventions have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Variations or modifications to the formulation of this invention, within the scope of the invention, may occur to those skilled in the art upon reviewing the disclosure herein. Such variations or modifications are well within the spirit of this invention.
The numerical values given for various physical parameters, dimensions, and quantities are only approximate values and it is envisaged that the values higher than the numerical value assigned to the physical parameters, dimensions and quantities fall within the scope of the invention unless there is a statement in the specification to the contrary.
While considerable emphasis has been placed herein on the specific features of the preferred embodiment, it will be appreciated that many additional features can be added and that many changes can be made in the preferred embodiment without departing from the principles of the disclosure. These and other changes in the preferred embodiment of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation. ,
Claims:WE CLAIM:
1. A bimetallic catalyst system comprising an adduct of a titanium tetraalkoxide and a magnesium salt.
2. The bimetallic catalyst system as claimed in claim 1, wherein said titanium tetraalkoxide is selected from the group consisting of titanium tetraethoxide, titanium tetraisopropoxide, titanium tetramethoxide, titanium tetrabutoxide, and titanium tetraisobutoxide.
3. The bimetallic catalyst system as claimed in claim 1, wherein said magnesium salt is selected from the group consisting of magnesium dichloride and magnesium acetate.
4. The bimetallic catalyst system as claimed in claim 1, wherein a weight ratio of said magnesium salt to said titanium tetraalkoxide is in the range of 0.005:1 to 0.1:1.
5. A process for the preparation of a bimetallic catalyst system, said process comprising the following steps:
i. mixing a magnesium salt and a titanium tetraalkoxide in a predetermined weight ratio to obtain a mixture;
ii. heating said mixture to a first predetermined temperature for a first predetermined time period to obtain a homogenous mixture; and
iii. cooling said homogenous mixture to a temperature in the range of 25 °C to 35 °C under an inert atmosphere to obtain said bimetallic catalyst system comprising an adduct of titanium tetraalkoxide and magnesium salt.
6. The process as claimed in claim 5, wherein said magnesium salt is selected from the group consisting of magnesium dichloride and magnesium acetate.
7. The process as claimed in claim 5, wherein said titanium tetraalkoxide is selected from the group consisting of titanium tetraethoxide, titanium tetraisopropoxide, titanium tetramethoxide, titanium tetrabutoxide, and titanium tetraisobutoxide.
8. The process as claimed in claim 5, wherein said predetermined weight ratio of said magnesium salt to said titanium tetraalkoxide is in the range of 0.005:1 to 0.1:1.
9. The process as claimed in claim 5, wherein said first predetermined temperature is in the range of 70 °C to 120 °C.
10. The process as claimed in claim 5, wherein said first predetermined time period is in the range of 3 hours to 10 hours.
11. A process for the preparation of a biodegradable polymer, said process comprising the following steps:
a) mixing a bimetallic catalyst system as claimed in claim 1 and monomers in a predetermined weight ratio at a temperature in the range of 25 °C to 35 °C under stirring to obtain a mixture;
b) heating said mixture under stirring at a second predetermined temperature for a second predetermined time period to obtain a product mixture; and
c) cooling said product mixture to a temperature in the range of 25 °C to 35 °C to obtain said biodegradable polymer.
12. The process as claimed in claim 11, wherein said second predetermined temperature is in the range of 150 °C to 280 °C.
13. The process as claimed in claim 11, wherein said second predetermined time period is in the range of 2 hours to 12 hours.
14. The process as claimed in claim 11, wherein said monomer is selected from aliphatic acid and its ester derivatives, aromatic acid and its ester derivatives and diol compound.
15. The process as claimed in claim 14, wherein a molar ratio of said aliphatic acid or its ester derivatives, to said aromatic acid or its ester derivatives is in the range of 1:0.5 to 1:2.
16. The process as claimed in claim 14, wherein
• said aliphatic acid is at least one selected from the group consisting of oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, brassylic acid, tetradecanedioic acid, 1,3-cyclopentanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, diglycolic acid, itaconic acid, maleic acid and fumaric acid;
• said aliphatic acid ester derivative is at least one selected from the group consisting of methyl, ethyl, propyl and isopropyl ester derivatives of oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, brassylic acid, tetradecanedioic acid, 1,3-cyclopentanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, diglycolic acid, itaconic acid, maleic acid and fumaric acid.
17. The process as claimed in claim 14, wherein said aromatic acid or its ester derivative is at least one selected from the group consisting of terephthalic acid, dimethyl terephthalate, phthalic acid, phthalic anhydride, isophthalic acid, dimethyl isophthalate, 4-methylphthalic acid, 4-methylphthalic anhydride, dimethyl phthalate, naphthalene dicarboxylic acid and diphenyl ether dicarboxylic acid.
18. The process as claimed in claim 14, wherein said diol compound is at least one selected from the group consisting of ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2,4-dimethyl-2-ethyl-1,3-hexanediol, 2,2-dimethyl-1,3-propanediol, 2-ethyl-2-butyl-1,3-propanediol, 2-ethyl-2-isobutyl-1,3-propanediol and 2,2,4-trimethyl-1,6-hexanediol, 1,2-cyclopentanediol, 1,2-cyclohexanediol, 1,4-cyclohexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol and 1,4-cyclohexanedimethanol.
19. The process as claimed in claim 11, wherein said biodegradable polymer is selected from the group consisting of polybutylene adipate terephthalate (PBAT), polybutylene succinate (PBS), poly(butyl adipate) (PBA), polybutylene succinate terephthalate (PBST).
20. The process as claimed in claim 11, wherein an amount of said bimetallic catalyst system is in the range of 0.5% to 2% with respect to the total weight of said monomers.
Dated this 20th day of April, 2024

_______________________________
MOHAN RAJKUMAR DEWAN, IN/PA – 25
of R.K.DEWAN & CO.
Authorized Agent of Applicant

TO,
THE CONTROLLER OF PATENTS
THE PATENT OFFICE, AT MUMBAI