DESC:FIELD:
The present disclosure relates to synthesis of thermoplastic polymer using carbon dioxide.

BACKGROUND:
Society is confronted with global warming, which is due to the increasing accumulation of carbon dioxide (CO2) in the atmosphere. This results in climate change and serious environmental problems, which are closely correlated with greenhouse gas emissions from human activities. Among the greenhouse gases, carbon dioxide contributes more than 60% to global warming because of its huge emission amount.
Moreover, the concentration of carbon dioxide in the atmosphere is continuously increasing, thus fueling the already existing public concerns and impact on global warming. Therefore, the absorption/adsorption, utilization and transformation of carbon dioxide into useful chemicals, polymers/copolymers as an alternative feed stock, is an area of great interest.
Remediation strategies that convert carbon dioxide into other materials such as thermoplastic polymer are greatly preferred as they offer the potential to create new commercially viable products from a source of waste.
Thus, there is felt a need to provide a process for the synthesis of thermoplastic polymer using carbon dioxide.
OBJECTS:
Some of the objects of the present disclosure aimed to ameliorate one or more problems of the prior art or to at least provide a useful alternative are listed herein below.
An object of the present disclosure is to provide a simple and economic process for synthesizing thermoplastic polymer using carbon dioxide.
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 provides a process for preparing a thermoplastic polymer from carbon dioxide and at least one diolefin. The process of the present disclosure comprises the following steps.
A dried hermetically sealed reactor is fed with at least one first fluid medium, at least one transition metal catalyst and at least one phosphorus (III) compound. The resultant mixture is cooled to a temperature in a range of -20 ?C to 0 ?C, followed by charging at least one diolefin to the reactor to attain a first predetermined pressure. The reactor is maintained under the first predetermined pressure for 1 to 2 hours, to obtain a first reaction mixture. Carbon dioxide is introduced into the reactor to attain a second predetermined pressure and the reactor is maintained under the second predetermined pressure for 30 to 60 minutes to obtain a second reaction mixture. The second reaction mixture is heated in a predetermined manner to attain a temperature in the range of 60 to 90?C, and further heated for a time period of 4 to 8 hours, followed by cooling the reactor, depressurizing the reactor, and separating the first fluid medium to obtain a lactone. The lactone is polymerized using at least one free radical initiator at a temperature in the range of 80 to 120?C for a time period of 12 to 36 hours to obtain a product mass containing the thermoplastic polymer. The product mass is mixed with at least one second fluid medium and agitated to obtain a suspension comprising a solid mass containing the thermoplastic polymer and a liquid phase. The solid mass is separated from the suspension, washed and dried to obtain the thermoplastic polymer.
In accordance with the embodiments of the present disclosure, the diolefin is selected from the group consisting of butadiene, isoprene, 1,3-octadiene, and 1,3-hexadiene. In accordance with one embodiment of the present disclosure, the diolefin is butadiene.
In accordance with the embodiments of the present disclosure, the polymerization of lactone is carried out along with at least one co-monomer selected from the group consisting of aliphatic monomers containing at least one vinyl functional group and aromatic monomers containing at least one vinyl functional group. The thermoplastic polymer obtained is a co-polymer of lactone and the co-monomer.
In accordance with one embodiment of the present disclosure, the polymerization of lactone is carried out along with styrene as a co-monomer. The ratio of the amount of lactone and the amount of styrene is in the range from 1:1 to 1:9.
In accordance with the embodiments of the present disclosure, the ratio of the amount of carbon dioxide to the amount of the diolefin is 1:2.
In accordance with the embodiments of the present disclosure, the first predetermined pressure is in the range of 0.5 to 2 bar and the second predetermined pressure is in the range of 2 to 5 bar.
In accordance with the embodiments of the present disclosure, the first fluid medium is at least one selected from the group of polar aprotic fluid media consisting of acetonitrile, tetrahydrofuran, and ethylene carbonate. In accordance with the embodiments of the present disclosure, the transition metal catalyst is selected from the group of palladium based catalysts consisting of palladium acetylacetonate, palladium acetate, palladium-Schiff base complexes. The ratio of the amount of transition metal catalyst to the first fluid medium is in the range of 0.05 to 0.2% weight/volume.
In accordance with the embodiments of the present disclosure, the phosphorus (III) compound is at least one selected from the group consisting of triphenylphosphine, and triphenyl phosphite. The molar ratio of the phosphorus (III) compound to the transition metal catalyst is in the range from 1:1 to 1:3.
In accordance with the embodiments of the present disclosure, the step of heating the second reaction mixture in a predetermined manner includes increasing the temperature of the second reaction mixture in steps of 15 ?C after every 20 minutes to attain the temperature in the range of 60 to 90?C.
In accordance with the embodiments of the present disclosure, the lactone is a six membered cyclic d-lactone.
In accordance with the embodiments of the present disclosure, the free radical initiator is selected from a group consisting of azobis(isobutyronitrile) and 1,1'-azobis(cyclohexane-1-carbonitrile). The ratio of the amount of free radical initiator to the amount of the lactone is in the range of 0.001 to 0.1%.
In accordance with the embodiments of the present disclosure, the second fluid medium is at least one selected from the group consisting of methanol, ethanol, and propanol.

DETAILED DESCRIPTION:
The present disclosure provides a process for synthesis of a thermoplastic polymer using carbon dioxide and diolefin.
In an aspect, the present disclosure provides a process for preparing a thermoplastic polymer from carbon dioxide and at least one diolefin. The process involves the following steps.
The process of the present disclosure is carried out using a dried hermetically sealed reactor. The reactor is charged with at least one first fluid medium, at least one transition metal catalyst and at least one phosphorus (III) compound, and the resultant mixture is cooled to a temperature in a range of -20 ?C to 0 ?C. At this temperature, at least one diolefin is charged to the reactor to attain a first predetermined pressure, followed by agitating the reactor under the first predetermined pressure for 1 to 2 hours to obtain a first reaction mixture. During this time period the diolefin dissolves in the first fluid medium.
In accordance with the embodiments of the present disclosure, the diolefin is selected from the group consisting of butadiene, isoprene, 1,3-octadiene, and 1,3-hexadiene. In accordance with one embodiment of the present disclosure, the diolefin is butadiene.
CO2 is introduced into the reactor to attain a second predetermined pressure, followed by agitating the reactor under the second predetermined pressure for 30 to 60 minutes to obtain a second reaction mixture. During this time period CO2 dissolves in the first reaction medium.
In accordance with the embodiments of the present disclosure, the first predetermined pressure is in the range of 0.5 to 2 bar and the second predetermined pressure is in the range of 2 to 5 bar.
In accordance with the embodiments of the present disclosure, the ratio of the amount of carbon dioxide to the amount of the diolefin is 1:2.
The second reaction mixture is heated in a predetermined manner to attain a temperature in the range of 60 to 90?C, followed by heating for a time period of 4 to 8 hours to obtain a mixture containing a lactone. The reactor is depressurized, and the first fluid medium is separated from the mixture to obtain a lactone.
In accordance with one embodiment of the present disclosure, the lactone is a six membered cyclic d-lactone.
In accordance with the embodiments of the present disclosure, the heating in a predetermined manner includes increasing the temperature of the second reaction mixture in steps of 15 ?C after every 20 minutes to attain the temperature in the range of 60 to 90 ?C.
The lactone is polymerized using at least one free radical initiator and at a temperature in the range of 80 to 120 ?C for a time period of 12 to 36 hours to obtain a product mass containing the thermoplastic polymer.
The product mass is mixed with at least one second fluid medium to obtain a suspension comprising a solid mass containing the thermoplastic polymer and a liquid phase. The solid mass is separated from the suspension, washed and dried to obtain the thermoplastic polymer.
In accordance with the embodiments of the present disclosure, the first fluid medium is at least one selected from the group of polar aprotic solvents consisting of acetonitrile, tetrahydrofuran, and ethylene carbonate.
In accordance with one embodiment of the present disclosure, the first fluid medium is acetonitrile.
In accordance with the embodiments of the present disclosure, the transition metal catalyst is selected from the group of palladium based catalysts consisting of palladium acetylacetonate, palladium acetate, and palladium-Schiff base complexes. In accordance with one embodiment of the present disclosure, the catalyst is palladium acetylacetonate.
In accordance with the embodiments of the present disclosure, the ratio of the amount of the transition metal catalyst to the amount of the first fluid medium is in the range of 0.05 to 0.2% weight/volume.
In accordance with the embodiments of the present disclosure, the phosphorus (III) compound is at least one selected from the group consisting of triphenylphosphine, and triphenyl phosphite. In accordance with one embodiment of the present disclosure, the phosphorus (III) compound is triphenylphosphine.
In accordance with the embodiments of the present disclosure, the molar ratio of the phosphorus (III) compound to the transition metal catalyst is in the range from 1:1 to 1:3.
In accordance with the embodiments of the present disclosure, the step of obtaining the lactone optionally involves a purification step. The purification is carried out by a suitable method such as distillation.
In accordance with the embodiments of the present disclosure, the first fluid medium separated from the lactone formation step can be recovered and reused.
In accordance with the embodiments of the present disclosure, the free radical initiator is selected from the group consisting of azobis(isobutyronitrile) and 1,1'-azobis(cyclohexane-1-carbonitrile). The ratio of the amount of free radical initiator to the amount of the lactone is in the range of 0.001 to 0.1%.
In accordance with the embodiments of the present disclosure, the polymerization of lactone is carried out along with at least one co-monomer selected from the group consisting of aliphatic monomers containing at least one vinyl functional group and aromatic monomers containing at least one vinyl functional group. The thermoplastic polymer obtained in this case is a co-polymer of lactone and the co-monomer.
In accordance with one embodiment of the present disclosure, the polymerization of lactone is carried out along with styrene as a co-monomer. The ratio of the amount of lactone and the amount of styrene is in the range from 1:1 to 1:9.
Thermoplastic polymer with requisite thermal properties, mechanical properties, weather resistance and the like can be obtained by incorporating a suitable co-monomer in the polymerization step.
In accordance with the embodiments of the present disclosure, the free radical polymerization process can be carried out in the form of an emulsion process, a solution process or a bulk process.
In accordance with one embodiment of the present disclosure, thermoplastic polymer obtained by the process of the present disclosure can have thermal stability up to 400 °C.
In accordance with the embodiments of the present disclosure, the second fluid medium is at least one selected from the group consisting of methanol, ethanol, and propanol. In accordance with one embodiment of the present disclosure, the second fluid medium is methanol.
The process of the present disclosure provides a simple and economic process for synthesizing thermoplastic polymer using carbon dioxide. Further, the process of the present disclosure provides thermoplastic polymer with high incorporation of carbon dioxide. Furthermore, the process of the present disclosure is carried out at low pressure.
The present disclosure is further illustrated herein below with the help of the following experiments. The experiments used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the experiments should not be construed as limiting the scope of embodiments herein.
These laboratory scale experiments can be extrapolated to industrial/commercial scale.
Experiments
Experiment 1:
A thermoplastic polymer was synthesized using carbon dioxide and butadiene. The ratio of the amount of carbon dioxide to the amount of butadiene was 1:2.
A reactor was dried by simultaneously heating and cooling cycles along with nitrogen (N2) gas purging. The reactor was closed and charged with acetonitrile and Pd(acac)2 with triphenylphosphine. The reactor was cooled to -8oC and charged with butadiene, till a pressure of 1.5 bar was attained in the reactor. The reaction was maintained under this pressure for 1 hour. CO2 was charged into the reactor at -8oC till a pressure of 2.5 bar was attained in the reactor and the reactor was maintained at this pressure for 30 minutes.
The temperature of the reaction mixture was increased in steps of 15 oC at an interval of 20 minutes up to 70 oC while maintaining the reactor pressure at 2.5 bar. The reaction was continued for 5 hours and then the reactor was cooled to room temperature, and depressurized. The product mass was vacuum dried to remove the volatile liquids and obtain the lactone.
The lactone was then mixed with azobisisobutyronitrile (AIBN) in a round bottom flask fitted with a condenser in an oil bath with a magnetic stirrer and heated at 100 oC for 24 hours. The reaction mixture was cooled and 100 ml of methanol was added to the reaction mixture. The precipitate obtained was collected by filtration and washed several times with 100 ml demineralized water and 100 ml methanol. The washed precipitate was then dried under reduced pressure in an oven at 60 oC to obtain the thermoplastic polymer.
Experiment 2:
Copolymerization of Lactone with styrene
Lactone was prepared by the process mentioned in Experiment 1.
In a dried reactor fitted with a condenser, were charged lactone (5.0 g) and styrene (7.0 g) in 1:1 molar ratio, under nitrogen atmosphere. AIBN initiator (0.002 g) was added to the reactor and the reaction mixture was heated up to 120 °C for 12 hours. The reaction mixture was cooled to room temperature and poured in methanol. The precipitate obtained was collected and washed several times with methanol and water. Finally, the product was dried in vacuum oven at 100 °C for 2 hours. The polymer obtained was characterized by Fourier transform- infra red (FT-IR), nuclear magnetic resonance (NMR), X- ray defraction (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and GPC analysis. The characterization confirms the formation of the copolymer of lactone and styrene.
TECHNICAL ADVANCEMENTS AND ECONOMICAL SIGNIFICANCE:
The technical advancements offered by the present disclosure include the realization of a process:
? for synthesizing thermoplastic polymer using carbon dioxide and diolefin in a simple and economic manner;
? which helps in high incorporation of carbon dioxide in the polymer;
? that is carried out at low pressure;
? that provides a thermoplastic polymer having thermal stability up to 400°C.
? that provides a copolymer of lactone with another aliphatic diolefin or aromatic co-monomer.
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 mentioned for the various physical parameters, dimensions or quantities are only approximations and it is envisaged that the values higher/lower than the numerical values assigned to the parameters, dimensions or quantities fall within the scope of the disclosure, unless there is a statement in the specification specific 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:1. A process for preparing a thermoplastic polymer using carbon dioxide and at least one diolefin, the process comprising:
a. providing a dried hermetically sealed reactor, feeding the reactor with at least one first fluid medium, at least one transition metal catalyst and at least one phosphorus (III) compound, and cooling the resultant mixture to a temperature in a range of -20 ?C to 0 ?C, followed by charging at least one diolefin to the reactor to attain a first predetermined pressure and maintaining the reactor under the first predetermined pressure for 1 to 2 hours, to obtain a first reaction mixture;
b. introducing CO2 into the reactor to attain a second predetermined pressure and maintaining the reactor under the second predetermined pressure for 30 to 60 minutes to obtain a second reaction mixture;
c. heating the second reaction mixture in a predetermined manner to attain a temperature in the range of 60 to 90?C, and heating for a time period of 4 to 8 hours, cooling the reactor, depressurizing the reactor, followed by separating the first fluid medium to obtain a lactone; and
d. polymerizing the lactone using at least one free radical initiator at a temperature in the range of 80 to 120?C for a time period of 12 to 36 hours to obtain a product mass containing the thermoplastic polymer; and
e. mixing the product mass with at least one second fluid medium and agitating to obtain a suspension comprising a solid mass containing the thermoplastic polymer and a liquid phase, separating the solid mass from the suspension, washing the separated solid mass followed by drying to obtain the thermoplastic polymer.

2. The process as claimed in claim 1, wherein the diolefin is selected from the group consisting of butadiene, isoprene, 1,3-octadiene, and 1,3-hexadiene.

3. The process as claimed in claim 1, wherein the polymerization of lactone is carried out along with at least one co-monomer selected from the group consisting of aliphatic monomers containing at least one vinyl functional group, and aromatic monomers containing at least one vinyl functional group, and the thermoplastic polymer obtained is a co-polymer of lactone and the co-monomer.

4. The process as claimed in claim 3, wherein the polymerization of lactone is carried out along with styrene as a co-monomer, and the ratio of the amount of lactone and the amount of styrene is in the range from 1:1 to 1:9.

5. The process as claimed in claim 1, wherein the ratio of the amount of carbon dioxide to the amount of the diolefin is 1:2.
6. The process as claimed in claim 1, wherein the first predetermined pressure is in the range of 0.5 to 2 bar and the second predetermined pressure is in the range of 2 to 5 bar.

7. The process as claimed in claim 1, wherein the first fluid medium is at least one selected from the group consisting of acetonitrile, tetrahydrofuran, and ethylene carbonate.

8. The process as claimed in claim 1, wherein the transition metal catalyst is selected from the group of palladium based catalysts consisting of palladium acetylacetonate, palladium acetate, and palladium-Schiff base complexes and the ratio of the amount of transition metal catalyst to the amount of the first fluid medium is in the range of 0.05 to 0.2% weight/volume.

9. The process as claimed in claim 1, wherein the phosphorus (III) compound is at least one selected from the group consisting of triphenylphosphine, and triphenyl phosphite, and the molar ratio of the phosphorus (III) compound to the transition metal catalyst is in the range from 1:1 to 1:3.

10. The process as claimed in claim 1, wherein the step of heating the second reaction mixture in a predetermined manner includes increasing the temperature of the second reaction mixture in steps of 15 ?C after every 20 minutes to attain the temperature in the range of 60 to 90?C.
11. The process as claimed in claim 1, wherein the lactone is a six membered cyclic d-lactone.

12. The process as claimed in claim 1, wherein the free radical initiator is selected from a group consisting of azobis(isobutyronitrile) and 1,1'-azobis(cyclohexane-1-carbonitrile), and the ratio of the amount of free radical initiator to the amount of the lactone is in the range of 0.001 to 0.1%.

13. The process as claimed in claim 1, wherein the second fluid medium is at least one selected from the group consisting of methanol, ethanol, and propanol.