Description:FIELD
The present disclosure relates to a process for the preparation of an elastomeric ionomer.
DEFINITIONS
As used in the present disclosure, the following terms are generally intended to have the meaning as set forth below, except to the extent that the context in which they are used indicates otherwise.
Ionomer: The term “Ionomer” refers to a class of polymers that comprises repeating units of electrically neutral units and a fraction of ionized units that are covalently bonded to the backbone of the polymer.
Nucleophile: The term “Nucleophile” refers to a chemical species which comprises an electron pair and can form a bond by donating the electron pair.
Mooney viscosity: The term “Mooney viscosity” refers to a measurement of the viscosity of a rubber or compound, determined in a Mooney shearing disk viscometer. Mooney viscosity differentiates between different types and grades of polymers in order to ensure a high processing consistency.
Endo–exo isomerism: The term “endo-exo isomerism” refers to a special type of stereoisomerism found in organic compounds with a substituent on a bridged ring system. The prefix “endo” is reserved for the isomer with the substituent located closest, or "syn", to the longest bridge. The prefix “Exo” is reserved for the isomer with the substituent located farthest, or "anti", to the longest bridge.
BACKGROUND
The background information herein below relates to the present disclosure but is not necessarily prior art.
Butyl rubber (IIR) is a copolymer of isobutylene and isoprene. It is obtained by cationic polymerization and contains approximately 1 mol% to 2 mol% of isoprene units. The small amount of isoprene helps in vulcanization due to unsaturation contents, and isobutylene provides high chemical stability and low permeability to the gases in butyl rubber.
However, due to less amount of unsaturation (1 to 2 mol%), butyl rubber (IIR) has a low cure rate, poor adhesion, and compatibility with unsaturated rubber. The isoprene in butyl rubber can be modified through halogenation to form a reactive halide functionality which greatly improves its reactivity towards sulfur and other nucleophiles. Halogenated butyl rubber (HIIR), includes chlorinated IIRs (CIIRs) and brominated IIRs (BIIRs). The BIIR is obtained by introducing bromine atoms near the double bonds of the IIR molecular chain, which greatly increases the cure reactivity of the double bonds and the polarity of the molecular chain simultaneously. BIIR is mainly used in the automotive industry (inner tubes, curing bladders, body mounts) as well as for electrical insulation and roof sheets.
The treatment of brominated butyl rubber (BIIR) with nitrogen based nucleophiles and/or phosphorus based nucleophiles, leads to the generation of butyl rubber-based ionomers. The butyl rubber based ionomers are the elastomeric ionomers which provide many advantages such as exceptional air impermeability, superior oxidative stability, unique dampening characteristics, and the like. However, in the conventional process of preparing butyl rubber based ionomers, the nucleophiles mixed with the halogenated butyl rubber are not utilized completely, resulting in an unreacted nucleophile. The unreacted nucleophile remains present in the ionomer as a residue which reacts with the oxidizing agents to form an oxidative derivative of the nucleophile. This oxidative derivative of the nucleophile adversely affects the properties of the rubber during the vulcanization process. Further, the conventional process for the preparation of butyl rubber based ionomers (ionomeric elastomers) are solvent based processes that are associated with the drawback of additional workup steps which makes the entire process expensive and complex.
Therefore, there is felt a need to provide a simple, efficient, and ecofriendly process for the preparation of elastomeric ionomers that obviates the drawbacks mentioned hereinabove or at least provides an alternative solution.
OBJECTS
Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows.
An object of the present disclosure is to ameliorate one or more problems of the background or to at least provide a useful alternative.
Another object of the present disclosure is to provide a process for the preparation of an elastomeric ionomer.
Still another object of the present disclosure is to provide a simple, efficient and environment friendly process for the preparation of an elastomeric ionomer.
Yet another object of the present disclosure is to provide a process for the preparation of elastomeric ionomer that has improved mechanical properties.
Another object of the present disclosure is to provide a solvent free process for the preparation of an elastomeric ionomer.
Yet another object of the present disclosure is to provide a solvent free melt mixing process for the preparation of an elastomeric ionomer.
Still another object of the present disclosure is to provide a process for the preparation of an elastomeric ionomer without generating by-products.
Yet another object of the present disclosure is to provide a process for the preparation of an elastomeric ionomer with improved Mooney viscosity.
Still another object of the present disclosure is to provide a process for the preparation of an elastomeric ionomer with improved strength.
Yet another object of the present disclosure is to provide a process for the preparation of an elastomeric ionomer with self-healing characteristics which are required for the long life of tires.
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 process for the preparation of an elastomeric ionomer. The process comprises heating a predetermined amount of halobutyl rubber in a preheated mixer at a first predetermined temperature under stirring at a first predetermined speed for a first predetermined time period to obtain a mass. A predetermined amount of a nucleophile is added to the mass followed by raising the temperature of the mixer to a second predetermined temperature under stirring at a second predetermined speed for a second predetermined time period to obtain the elastomeric ionomer.
In an embodiment of the present disclosure, the halobutyl rubber is at least one selected from the group consisting of bromobutyl rubber, and chlorobutyl rubber.
In an embodiment of the present disclosure, the halobutyl rubber contains exo halide unit in an amount in the range of 1.2 mol% to 1.5 mol%.
In an embodiment of the present disclosure, the conversion of the exo-halobutyl rubber to an endo-halobutyl rubber is in the range of 70 mol% to 95 mol%.
In an embodiment of the present disclosure, the halobutyl rubber is characterized by having:
i) a Mooney viscosity ML(1+3) @127 °C in the range of 25 MU to 60 MU;
ii) an isoprene content in the range of 0.1% to 7.0% unsaturation; and
iii) a halogen content in the range of 0.2 mole% to 7 mole%.
In an embodiment of the present disclosure, the mixer is selected from an internal mixer, an extruder, and a two roll mill.
In an embodiment of the present disclosure, the mixer is preheated at a temperature in the range of 50 °C to 90 °C.
In an embodiment of the present disclosure, the first predetermined temperature is in the range of 50 °C to 90 °C.
In an embodiment of the present disclosure, the first predetermined speed is in the range of 20 rpm to 60 rpm.
In an embodiment of the present disclosure, the first predetermined time period is in the range of 2 minutes to 10 minutes.
In an embodiment of the present disclosure, the nucleophile is a nitrogen containing nucleophile.
In an embodiment of the present disclosure, the nucleophile is at least one selected from the group consisting of pyridine, 4-ethyl pyridine, 2-aminopyridine, nitropyridine, and dimethyl aminopyridine.
In an embodiment of the present disclosure, the mass ratio of said halobutyl rubber to said nucleophile is in the range of 100:0.1 to 100:3.
In an embodiment of the present disclosure, the second predetermined temperature is in the range of 90 °C to 160 °C.
In an embodiment of the present disclosure, the second predetermined speed is in the range of 40 rpm to 80 rpm.
In an embodiment of the present disclosure, the second predetermined time period is in the range of 5 minutes to 20 minutes.
In an embodiment of the present disclosure, the predetermined torque is maintained during the addition of the nucleophile.
In an embodiment of the present disclosure, the predetermined torque is in the range of 15 Nm to 30 Nm.
In an embodiment of the present disclosure, the elastomeric ionomer is a pyridinium based ionomer.
In an embodiment of the present disclosure, the elastomeric ionomer is characterized by having:
i) a Mooney viscosity ML(1+3) @127 °C is in the range of 35 MU to 120 MU; and
ii) an ionic content in the range of 0.1 mol% to 0.8 mol%.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
The present disclosure will now be described with the help of the accompanying drawing, in which:
FIGURE 1 illustrates time vs. torque profile for the preparation of pyridinium ionomers by melt mixing process using different phr of 4-dimethylaminopyridine (DMAP) as nucleophile in accordance with the present disclosure;
FIGURE 2 illustrates 1H NMR spectrum of (A) pyridinium bromo butyl ionomer (PyIIR) and (B) brominated butyl rubber (BIIR) showing the formation of elastomeric ionomer in accordance with the present disclosure; and
FIGURE 3 illustrates ionic cluster formation in accordance with the present disclosure.
DETAILED DESCRIPTION
The present disclosure relates a process for the preparation of an elastomeric ionomer.
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.
As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed elements.
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.
Butyl rubber (IIR) is a copolymer of isobutylene and isoprene. It is obtained by the cationic polymerization and contains approximately 1 mol% to 2 mol% of isoprene units. The small amount of isoprene helps in vulcanization due to unsaturation contents, and isobutylene provides high chemical stability and low permeability to the gases in butyl rubber.
However, due to less amount of unsaturation (1 mol% to 2 mol%), butyl rubber (IIR) has a low cure rate, poor adhesion, and compatibility with unsaturated rubber. The isoprene in butyl rubber can be modified through halogenation to form a reactive halide functionality which greatly improves its reactivity towards sulfur and other nucleophiles. Halogenated butyl rubber (HIIR), includes chlorinated IIRs (CIIRs) and brominated IIRs (BIIRs). The BIIR is obtained by introducing bromine atoms near the double bonds of the IIR molecular chain, which greatly increases the cure reactivity of the double bonds and the polarity of the molecular chain simultaneously. BIIR is mainly used in the automotive industry (inner tubes, curing bladders, body mounts) as well as for electrical insulation and roof sheeting.
The treatment of brominated butyl rubber (BIIR) with nitrogen based nucleophiles and/or phosphorus based nucleophiles, leads to the generation of butyl rubber-based ionomers. The butyl rubber based ionomers are the elastomeric ionomers which provide many advantages such as exceptional air impermeability, superior oxidative stability, unique dampening characteristics and the like. However, in the conventional process of preparing butyl rubber based ionomers, the nucleophiles mixed with the halogenated butyl rubber are not utilized completely, resulting in an unreacted nucleophile. The unreacted nucleophile remains present in the ionomer as a residue which reacts with the oxidizing agents to form an oxidative derivative of the nucleophile. This oxidative derivative of the nucleophile adversely affects the properties of the rubber during vulcanization process. Further, the conventional process for the preparation of butyl rubber based ionomers (ionomeric elastomers) are solvent based process that are associated with the drawback of additional workup steps which makes the entire process expensive and complex. The present disclosure provides process for the preparation of an elastomeric ionomer.
The process comprises the following steps:
a) heating a predetermined amount of halobutyl rubber in a preheated mixer at a first predetermined temperature under stirring at a first predetermined speed for a first predetermined time period to obtain a mass; and
b) adding a predetermined amount of a nucleophile to the mass followed by raising the temperature of the mixer to a second predetermined temperature under stirring at a second predetermined speed for a second predetermined time period to obtain the elastomeric ionomer.
The process is described in detail herein below.
In a first step a predetermined amount of halobutyl rubber is heated in a preheated mixer at a first predetermined temperature under stirring at a first predetermined speed for a first predetermined time period to obtain a mass.
In an embodiment of the present disclosure, the halobutyl rubber is at least one selected from the group consisting of bromobutyl rubber and chlorobutyl rubber. In an exemplary embodiment of the present disclosure, the halobutyl rubber is bromobutyl rubber.
In an embodiment of the present disclosure, the halobutyl rubber contains exo- halide unit in an amount in the range of 1.2 mol% to 1.5 mol%. In an exemplary embodiment, the halobutyl rubber contains exo-halide unit of 1.3 mol%.
In an embodiment of the present disclosure, the halobutyl rubber contains 75% to 80% of the exo-halobutyl rubber and 20% to 25% of endo-halobutyl rubber.
In an embodiment of the present disclosure, a conversion of the exo-halobutyl rubber to the endo-halobutyl rubber is in the range of 70 mol% to 95 mol%. In an exemplary embodiment, the conversion of the exo-bromo butyl rubber to the endo-bromo butyl rubber is 90 mol%.
The conversion of exo-halide unit to endo-halide unit takes place due to the heat supplied (first predetermined temperature) to the mixer and the torque generated during the mixing and thus avoiding the requirement of a catalyst for the conversion.
In an exemplary embodiment of the present disclosure, the conversion of the exo halobutyl rubber to the endo-halobutyl rubber is an in situ conversion.
In an embodiment of the present disclosure, the bromobutyl rubber is exo-bromobutyl rubber characterized by having:
i. a Mooney viscosity ML(1+3) @127 °C in the range of 25 MU to 60 MU;
ii. an isoprene content in the range of 0.1% to 7.0 % unsaturation; and
iii. a halogen content in the range of 0.2 mole% to 7 mole %.
In an exemplary embodiment of the present disclosure, the exo-bromobutyl rubber is characterized by having:
i. the Mooney viscosity ML(1+3) @127 °C of 32 MU;
ii. the isoprene content of 1.8 % unsaturation; and
iii. the bromine content of 1.6 mole%.
In an embodiment of the present disclosure, the mixer is selected from an internal mixer, extruder, and two roll mill. In an exemplary embodiment of the present disclosure, the mixer is an internal mixer.
In an embodiment of the present disclosure, the mixer is preheated at a temperature in the range of 50 °C to 90 °C to obtain a preheated mixer. In an exemplary embodiment, the mixer is preheated to 70 °C to obtain a preheated mixer.
In an embodiment of the present disclosure, the first predetermined temperature is in the range of 50 °C to 90 °C. In an exemplary embodiment of the present disclosure, the first predetermined temperature is 70 °C.
In an embodiment of the present disclosure, the first predetermined speed is in the range of 20 rpm to 60 rpm. In an exemplary embodiment of the present disclosure, the first predetermined speed is 40 rpm.
In an embodiment of the present disclosure, the first predetermined time period is in the range of 2 minutes to 10 minutes. In an exemplary embodiment of the present disclosure, the first predetermined time period is 3 minutes.
In the last step, a predetermined amount of a nucleophile is added to the mass followed by raising the temperature of the mixer to a second predetermined temperature under stirring at a second predetermined speed for a second predetermined time period to obtain the elastomeric ionomer.
In an embodiment of the present disclosure, the nucleophile is a nitrogen containing nucleophile.
In an embodiment of the present disclosure, the nitrogen containing nucleophile is at least one selected from the group consisting of pyridine, 4-ethyl pyridine, 2-aminopyridine, nitropyridine, and dimethyl aminopyridine (DMAP). In an exemplary embodiment, the nitrogen containing nucleophile is dimethyl aminopyridine (DMAP). In another exemplary embodiment, the nitrogen containing nucleophile is ethyl pyridine. In still another exemplary embodiment, the nitrogen containing nucleophile is 2-aminopyridine.
Dimethyl aminopyridine (DMAP) is a very strong and reactive nucleophile. It results in a faster reaction with endo-BIIR even at very low concentrations. Moreover, the incorporation of a small amount of ionic functionality (nucleophile) into butyl rubber improves the strength and mechanical properties of the elastomeric ionomer.
In an embodiment of the present disclosure, the nucleophile is used in an amount in the range of 0.1 phr to 5 phr, more preferably in the range of 0.1 phr to 3 phr. In an exemplary embodiment, the predetermined amount of the nucleophile is 0.35 phr. In another exemplary embodiment, the predetermined amount of the nucleophile is 0.75 phr.
In an embodiment of the present disclosure, the mass ratio of the halobutyl rubber to the nucleophile is in the range of 100:0.1 to 100:3. In an exemplary embodiment of the present disclosure, the mass ratio of the halobutyl rubber to the nucleophile is 100:0.35. In another exemplary embodiment of the present disclosure, the mass ratio of the halobutyl rubber to the nucleophile is 100:0.75.
The bromobutyl rubber is completely mixed and reacted with the nucleophile in an internal mixture/extruder/two roll mill which results in an elastomeric ionomer.
The increase in the BIIR/nucleophile ratio increases the strength of the elastomeric ionomer with increasing Mooney viscosity. A significant improvement in the strength of the elastomeric ionomer with desired Mooney viscosity is observed with 0.25 to 0.5 phr nucleophile (DMAP). While using a high phr of nucleophile results in a hard material which is difficult to process.
In an embodiment of the present disclosure, the second predetermined temperature is in the range of 90 °C to 160 °C. In an exemplary embodiment, the second predetermined temperature is 135 °C.
In an embodiment of the present disclosure, the second predetermined speed is in the range of 40 rpm to 80 rpm. In an exemplary embodiment, the second predetermined speed is 50 rpm.
In an embodiment of the present disclosure, the second predetermined time period is in the range of 5 minutes to 20 minutes. In an exemplary embodiment, the second predetermined time period is 12 minutes.
In an embodiment of the present disclosure, a predetermined torque is maintained during the addition of the nucleophile.
In an embodiment of the present disclosure, the predetermined torque is in the range of 15 Nm to 30 Nm at 5 minutes. In an exemplary embodiment, the predetermined torque is 17.8 Nm at 5 minutes. In another exemplary embodiment, the predetermined torque is 26.5 Nm at 5 minutes.
In an embodiment of the present disclosure, the elastomeric ionomer is a pyridinium based ionomer. In an exemplary embodiment, the elastomeric ionomer is a pyridinium based bromo butyl ionomer.
In an exemplary embodiment of the present disclosure, the process for the preparation of the elastomeric ionomer is represented as scheme I.

In accordance with the present disclosure, the synthesis of the elastomeric ionomers is by one step solvent free melt mixing process.
The solvent free process saves the solvent cost which is required for dissolution of rubber and its coagulations. Further, the absence of solvent eliminates the need for product workup steps.
The exo-bromobutyl rubber is in-situ converted into the reactive endo-bromobutyl rubber, which reacts with the nucleophile (DMAP) and results into polar elastomeric ionomer. During the reaction the temperature and torque of the internal mixture increases. The elastomeric ionomer is formed by the displacement of the halide group from the halo butyl rubber with a strong nitrogen based nucleophile (DMAP). A series of elastomeric ionomers are prepared by solvent free melt mixing process of the halobutyl rubber and the nucleophile (DMAP). The series of elastomeric ionomers indicates the ionomers of bromobutyl rubber by using different concentrations of DMAP nucleophile in an amount in the range of 0.2 phr to 2.5 phr and different nucleophiles such as 2-aminopyridine and 4-ethyl pyridine.
During conversion, the processability of the elastomeric ionomer is improved by optimizing the concentration of nucleophile in the range of 0.2 phr to 2.5 phr to achieve the pyridinium based ionomer (elastomeric ionomer) having Mooney viscosity Mooney viscosity ML(1+3) @127 °C in the desired range of 40 MU to 95 MU.
The ionic clusters in the elastomeric ionomer act as physical crosslinkers and resulted in higher Mooney viscosity. Elastomeric ionomers were formed by the ionic interactions between the pyridinium ion and bromide ion of the endo-bromo butyl ionomer. These ions together forms the ionic cluster, the same is illustrated in Figure 3.
The pyridinium based ionomer having ionic content in the range of 0.1 mol% to 0.8 mol%, preferably in the range of 0.1 mol% to 0.4 mol%.
In an embodiment of the present disclosure, the elastomeric ionomer is characterized by:
i) a Mooney viscosity ML(1+3) @127 °C in the range of 35 MU to 120 MU; and
ii) an ionic content in the range of 0.1 mol% to 0.8 mol%
In an exemplary embodiment of the present disclosure, the elastomeric ionomer is characterized by:
i) the Mooney viscosity ML(1+3) @127 °C of 66.5 MU; and
ii) the ionic content of 0.29 mol%.
In an embodiment of the present disclosure, the process is a solvent free process.
The solvent free process saves the solvent cost which is required for dissolution of rubber and its coagulations. Further, the absence of solvent eliminates the need for product workup steps.
The process of the present disclosure is a simple, efficient and ecofriendly to convert bromobutyl rubber to elastomeric ionomer in a single step process.
The elastomeric ionomer can be used in tire industries (tire inner liner) and pharmaceutical caps. The elastomeric ionomer is also used as sealants such as tire sealant, construction sealants, crack sealants and the like.
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 elastomeric ionomer (pyridinium based bromobutyl ionomer) (PyIIR) by melt mixing process by using dimethyl aminopyridine (DMAP) (nucleophile) in accordance with the present disclosure.
Hake internal mixer was preheated to 70°C to obtain a preheated internal mixer. 60 gm of bromobutyl rubber (halobutyl rubber) was added to the preheated internal mixer at 70°C (first predetermined temperature) at 40 rpm (first predetermined speed) for 3 minutes (first predetermined time period) to obtain a mass.
0.21 gm of dimethyl aminopyridine (DMAP) (nucleophile) was added to the mass followed by raising the temperature to 135 °C (second predetermined temperature) and maintaining a torque of 17.8 Nm at 50 rpm (second predetermined speed) for 5 minutes (second predetermined time period) to obtain the pyridinium based bromobutyl ionomer (PyIIR) (elastomeric ionomer).
The so obtained pyridinium based bromobutyl ionomer was passed through a two roll mill for preparing the elastomeric ionomer sheet.
The formation of pyridinium based bromobutyl ionomer is evident from figure 2. Figure 2 illustrates (A) 1H NMR spectrum of pyridinium based bromobutyl ionomer and (B) 1H NMR spectrum of brominated butyl rubber (BIIR). The reduction in exo-BIIR signal with an increase in endo-BBIR signal clearly indicated the formation of pyridinium based bromobutyl ionomer. During ionomer synthesis, first exo-BIIR is converted into endo-BIIR which reacts with a nucleophile to form pyridinium based bromobutyl ionomer.
Characterization of the pyridinium based bromo butyl rubber (PyIIR) (elastomeric ionomer) prepared in accordance with the present disclosure.
(a) Temperature or torque vs. time profile during the preparation of pyridinium based brominated butyl rubber (PyIIR) (elastomeric ionomer) by melt mixing process in accordance with the present disclosure.
Table 1 illustrates the brominated butyl rubber (BIIR)/DMAP (nucleophile) ratio for the preparation of pyridinium based brominated butyl rubber (PyIIR) (elastomeric ionomer).
Sample DMAP (phr) Mixing time Torque (Nm) at 5 min
BIIR 0 30 21.6
PyIIR-0.35 0.35 9 17.8
PyIIR-0.75 0.75 6 26.5
PyIIR-2.5 2.5 5 33.7

From table 1 it was evident that in case of a higher concentration of DMAP (nucleophile), the reaction temperature and torque increased rapidly which indicated that the reaction of BIIR with DMAP was very fast. In PyIIR-2.5 the torque of the internal mixer at 5 min was increased to 33.7 Nm which resulted in a hard material which was difficult to be processed. To control the temperature and torque of the internal mixture the concentration of DMAP was reduced to 0.75 phr and 0.35 phr. At this concentration, the reaction was softer and the material was processible. This indicated that the reaction become faster on increasing the DMAP content in the reaction.
Figure 1 illustrates the time vs. torque profile for the preparation of pyridinium based brominated butyl rubber (PyIIR) (elastomeric ionomer) by melt mixing process using different phr of DMAP as the nucleophile. From Figure 1 it was confirmed that in case of a higher concentration of DMAP (nucleophile), the reaction temperature and torque increased rapidly which indicated that the reaction of BIIR with DMAP was very fast.
(b) Gel Content
The gel content of PyIIR with different concentrations of DMAP was determined in toluene.
0.025 g of the elastomeric ionomer obtained in experiment 1 was dissolved in 25 ml of toluene and kept undisturbed for 24 hours to obtain a gel mixture. The gel mixture was filtered using a 325 mesh metal sieve to obtain the gel which was not dissolved in the toluene. The so obtained gel was dried and weighed. The results are summarized in Table 2.
Table 2: Pyridinium based brominated butyl rubber (PyIIR) (elastomeric ionomer) with different BIIR/DMAP ratios, Gel content, Mooney viscosity and microstructure (endo, exo, and ionomer mole%) by 1H NMR.
Sr.No Sample DMAP (phr) Gel content in Toluene (%) Mooney (ML1+3@127 °C) Microstructure by 1H NMR analysis
Exo (mol%) Endo (mol%) Ionomers (mol%)
1 BIIR 0 0.1 32
2 PyIIR-0.20 0.2 1.5 57.5 0.31 0.72 0.25
3 PyIIR-0.25 0.25 1.8 61.3 0.20 0.71 0.27
4 PyIIR-0.35 0.35 2.0 66.5 0.25 0.67 0.29
5 PyIIR-0.40 0.4 2.5 72.5 0.27 0.76 0.30
6 PyIIR-0.50 0.5 2.0 76 0.31 0.62 0.33
7 PyIIR-0.75 0.75 2.8 86 0.28 0.67 0.36
8 PyIIR-2.5 2.5 5.1 95.9 0.35 0.21 0.78
9 EtPyIIR-2.0 2.2 4.8 91 0.69 0.61 0.17
10 NH2PyIIR-0.9 0.9 4.8 81 0.46 0.57 0.14
EtPy = 4-ethyl pyridine, NH2Py = 2- aminopyridine

From table 2 it was observed that the ionic interactions increases with increasing DMAP (nucleophile) concentration and results in a higher gel content in PyIIR ionomers as compared to bromo butyl rubber (BIIR).
Further from table 2 it was observed that the gel content, Mooney viscosity and ionomer mol% increased with the increase in the DMAP concentration. The gel content, Mooney viscosity and ionomer mol% increased due to the increase in the elastomeric ionomer formation with the increase in the DMAP concentration. The gel content, Mooney viscosity, and ionomer mol% obtained by using the other nucleophile such as 4-ethyl pyridine and 2- aminopyridine was less which indicated that the elastomeric ionomer formation was less as compared to elastomeric ionomer formed by using DMAP (nucleophile).
(c) Mooney viscosity
The Mooney Viscosity of the elastomeric ionomer was measured by Mooney viscometer. It was observed that the ionic clusters in the elastomeric ionomer act as physical crosslinks and result in higher Mooney viscosity.
Further, from table 2 it was observed that the Mooney viscosity of PyIIR ionomers increases on increasing the DMAP ratio due to the presence of more ionic molecules and stronger ionic clusters.
(d) Mechanical properties
The mechanical properties such as self healing time, tensile strength, elongation at break, and hardness of the pyridinium based brominated butyl rubber (PyIIR) (elastomeric ionomer) was measured.
The tensile and elongation at break strength were measured by using ASTM D412, and hardness was measured by using ASTM D2240.
Table 3 illustrates the mechanical properties of the pyridinium based brominated butyl rubber (PyIIR) (elastomeric ionomer).
Sr. No Sample Self Healing time @100 ?C Tensile Strength, MPa Elongation at Break, % Hardness, Shore A
1 PyIIR-0.25 4 hours 1.2 >1500 27
2 BIIR Not healed 0.3 >1500 22
3 PyIIR-0.75 2 hours 4.2 1200 29
4 PyIIR-S-0.25 5 hour 1.0 1500 26
PyIIR-S: elastomeric ionomer obtained by solution process
From table 3 it was observed that the pyridinium based brominated butyl rubber (PyIIR) obtained by the process of the present disclosure has higher tensile strength and hardness as compared to the BIIR. Further, the self healing time @100 °C of pyridinium based brominated butyl rubber (PyIIR) obtained by the process of the present disclosure was 4 hours whereas the BIIR there was no healing observed.
Comparative examples
(a) Process for the preparation of the elastomeric ionomer by solution process.
100 gm of bromobutyl rubber (halobutyl rubber) was dissolved in 1 l of toluene (solvent) to make 10% solution followed by heating at 100 °C for 4 hours to obtain a first reaction mixture.
0.35 gm of dimethyl aminopyridine (DMAP) (nucleophile) was dissolved in 0.02 l of toluene (solvent) to obtain dissolved dimethyl aminopyridine. The dissolved dimethyl aminopyridine was added to the first reaction mixture followed by stirring at 400 rpm at 100 °C for 4 hours to complete the reaction and to obtain a second reaction mixture. The second reaction mixture was allowed to cool to room temperature (25 to 30 °C) to obtain a cooled second reaction mixture. The elastomeric ionomer was obtained by adding 800 ml of acetone in the so obtained cooled second reaction mixture for coagulation followed by drying under vacuum at 80 °C.
(b) Process for the preparation of the elastomeric ionomer using triphenylphosphine (PPh3).
The elastomeric ionomer was prepared by the same procedure as experiment no 1 except triphenylphosphine (PPh3) nucleophile was used. The elastomeric ionomer obtained was phosphonium bromo butyl ionomer (having triphenylphosphine content in the range of 0.2 phr – 2.5 phr).
It was observed that the elastomeric ionomer prepared by using triphenylphosphine nucleophile required a higher amount of PPh3 to reach the desired Mooney viscosity. Further, it was observed that by using 2.7 phr PPh3 either in solution or in melt mixing process the Mooney viscosity ML(1+3) @127 °C was 53 MU, while by using DMAP (in accordance with the present disclosure) the Mooney viscosity ML(1+3) @127 °C with 2.5 phr was 95 MU which was higher than the Mooney viscosity obtained by using 2.7 phr PPh3.
Table 4 demonstrates the torque of the elastomeric ionomer with different Nucleophile content.
Sr No Sample Nucleophile Nucleophile (phr) Mixing time (min) Max Torque (Nm)
1 BIIR - 0 30 21.6
2 PyIIR-0.35 DMAP 0.35 9 17.8
3 PyIIR-0.75 DMAP 0.75 6 26.5
4 PyIIR-2.5 DMAP 2.5 5 33.7
5 PPh3-IIR-2.7 PPh3 2.7 25 23.2
6 EtPyIIR-2.0 4-ethylpyridine 2.2 9 29
7 NH2PyIIR-0.9 2-aminopyridine 0.9 9 26
EtPy = 4-ethyl pyridine, NH2Py = 2- aminopyridine
From table 4 it was observed that by using DMAP based ionomer the torque increased significantly at lower concentrations. While other nucleophiles such as PPh3, 4-ethyl pyridine, and 2- aminopyridine requires high concentration to reach the same torque value. This indicates that the DMAP nucleophile results in a significant ionomeric conversion, leading to a higher torque compared to the other nucleophile.
(c) Process for the preparation of the elastomeric ionomer by using DMAP (nucleophile) in the range of 0.25 phr to 2.7 phr by solution process.
The elastomeric ionomer was prepared by the same procedure as comparative example (a) except the loading of nucleophile was in the range of 0.2 phr to 2.7 phr.
It was observed that the Mooney viscosity ML(1+3) @127 °C of the elastomeric ionomer obtained by the solution process with 2.7 phr nucleophile was found to be 92 MU which was lower than the Mooney viscosity ML(1+3) @127 °C of the elastomeric ionomer obtained by the melt mixing process with 2.7 phr nucleophile.
Table 5 demonstrates the Mooney viscosity of the elastomeric ionomer with different DMAP content obtained by the solution process.
Sr No Batch DMAP
(phr) Mooney viscosity (MU)
ML(1+3) @127 °C

1 PyIIR-S-2.7 2.7 92
2 PyIIR-S -1.4 1.4 64
3 PyIIR-S -0.5 0.5 56
4 PyIIR-S -0.35 0.35 52
5 PyIIR-S -0.25 0.25 49
PyIIR-S: elastomeric ionomer obtained by solution process
From table 5 it was observed that the Mooney viscosity obtained by using DMAP (nucleophile) in the solution process was less as compared to the Mooney viscosity obtained by using DMAP (nucleophile) in the melt mixing process. The lower value of Mooney viscosity indicates that the conversion of ionomer is less in the solution process as compared to the melt mixing process.
TECHNICAL ADVANCES AND ECONOMIC SIGNIFICANCE
The present disclosure described herein above has several technical advantages including, but not limited to, the realization of a process for the preparation of an elastomeric ionomer that:
• is solvent free;
• provides elastomeric ionomer with desired ionic functionality without the use of a catalyst;
• provides elastomeric ionomer with improved mechanical and self-healing properties;
• provides elastomeric ionomer that has ease of processability; and
• is simple, economical, and environment friendly.
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 components and component parts of the preferred embodiments, it will be appreciated that many embodiments can be made and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other changes in the preferred embodiment as well as other embodiments 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 process for the preparation of an elastomeric ionomer, said process comprising the following steps:
a. heating a predetermined amount of halobutyl rubber in a preheated mixer at a first predetermined temperature under stirring at a first predetermined speed for a first predetermined time period to obtain a mass; and
b. adding a predetermined amount of a nucleophile to said mass followed by raising the temperature of said mixer to a second predetermined temperature under stirring at a second predetermined speed for a second predetermined time period to obtain said elastomeric ionomer.
2. The process as claimed in claim 1, wherein said halobutyl rubber is at least one selected from the group consisting of bromobutyl rubber, and chlorobutyl rubber.
3. The process as claimed in claim 1, wherein said halobutyl rubber contains exo halide unit in an amount in the range of 1.2 mol% to 1.5 mol%.
4. The process as claimed in claim 3, wherein the conversion of exo-halobutyl rubber to endo-halobutyl rubber is in the range of 70 mol% to 95 mol%.
5. The process as claimed in claim 1, wherein said halobutyl rubber is characterized by having:
i) a Mooney viscosity ML(1+3) @127 °C in the range of 25 MU to 60 MU;
ii) an isoprene content in the range of 0.1 to 7.0 % unsaturation; and
iii) a halogen content in the range of 0.2 mole% to 7 mole%.
6. The process as claimed in claim 1, wherein said mixer is selected from an internal mixer, an extruder, and a two roll mill.
7. The process as claimed in claim 1, wherein said mixer is preheated at a temperature in the range of 50 °C to 90 °C.
8. The process as claimed in claim 1, wherein said first predetermined temperature is in the range of 50 °C to 90 °C.
9. The process as claimed in claim 1, wherein said first predetermined speed is in the range of 20 rpm to 60 rpm.
10. The process as claimed in claim 1, wherein said first predetermined time period is in the range of 2 minutes to 10 minutes.
11. The process as claimed in claim 1, wherein said nucleophile is a nitrogen containing nucleophile.
12. The process as claimed in claim 1, wherein said nucleophile is at least one selected from the group consisting of pyridine, 4-ethyl pyridine, 2-aminopyridine, nitropyridine, and dimethyl aminopyridine.
13. The process as claimed in claim 1, wherein a mass ratio of said halobutyl rubber to said nucleophile is in the range of 100:0.1 to 100:3.
14. The process as claimed in claim 1, wherein said second predetermined temperature is in the range of 90 °C to 160 °C.
15. The process as claimed in claim 1, wherein said second predetermined speed is in the range of 40 rpm to 80 rpm.
16. The process as claimed in claim 1, wherein said second predetermined time period is in the range of 5 minutes to 20 minutes.
17. The process as claimed in claim 1, wherein a predetermined torque is maintained during the addition of said nucleophile.
18. The process as claimed in claim 17, wherein said predetermined torque is in the range of 15 Nm to 30 Nm.
19. The process as claimed in claim 1, wherein said elastomeric ionomer is a pyridinium based ionomer.
20. The process as claimed in claim 1, wherein said elastomeric ionomer is characterized by having:
i) a Mooney viscosity ML(1+3) @127 °C is in the range of 35 MU to 120 MU; and
ii) an ionic content in the range of 0.1 mol% to 0.8 mol%

Dated this 31st day of July, 2023

_______________________________
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