Claims:WE CLAIM
1. A process for producing poly-isobutylene having exo-olefin content of at least 65 mol %, said process comprising the following steps:
- providing a feedstock comprising isobutylene monomer;
- providing a catalyst system comprising an ionic liquid and a fluid medium complex; and
- introducing said isobutylene monomer and said catalyst system to a reactor and polymerizing said isobutylene monomer under stirring at a temperature in the range of 0 °C to 30 °C to obtain said poly-isobutylene containing exo-olefin content of at least 65 mol %.
2. The process as claimed in claim 1, wherein said ionic liquid comprises a Lewis acid and a base.
3. The process as claimed in claim 2, wherein the ratio of said Lewis acid to said base is in the range of 1:1 to 5:1
4. The process as claimed in claim 1, wherein said feedstock is a hydrocarbon.
5. The process as claimed in claim 4, wherein said hydrocarbon is C4 raffinate containing 10 % to 90 % isobutylene monomer.
6. The process as claimed in claim 1, wherein the proportion of said catalyst system to said isobutylene monomer is in the range of 0.1 wt% to 1 wt%.
7. The process as claimed in claim 1, wherein said polyisobutylene has a number average molecular weight in the range of 800 g/mol to 2500 g/mol.
8. The process as claimed in claim 1, wherein the ratio of the weight average molecular weight and the number average molecular weight of said poly-isobutylene is in the range of 1 to 5.
9. The process as claimed in claim 1, wherein said Lewis acid is Group III element containing compound selected from the group consisting of AlCl3, BF3, GaCl3, and FeCl3.
10. The process as claimed in claim 1, wherein said base is selected from the group consisting of amides, urea and urea derivatives.
11. The process as claimed in claim 1, wherein said fluid medium is selected from the group consisting of benzene, toluene, chlorobenzene, cyclohexane, hexane, and dimethylformamide.
, Description:FIELD
The present disclosure relates to a process for preparing high reactive polyisobutylene.
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 indicate otherwise.
High Reactive Polyisobutylene (HRPIB): The term “high reactive polyisobutylene” refers to polyisobutylene having increased number of terminally positioned double bonds.
Exo-olefin: The term “exo-olefin” refers to terminal olefinic groups, such as methyl vinylidene that readily undergo chemical reactions.
BACKGROUND
The background information herein below relates to the present disclosure but is not necessarily prior art.
Polyisobutylene (PIB) [CAS No. 9003-27-4] is a synthetic rubber, or elastomer having the linear formula [CH2C(CH3)2]n. It is a polymer of isobutylene that is colorless to light yellow, elastic rubbery, semi-solid or viscous substance. It is odorless or has a slight characteristic odor, is non-toxic and is tasteless. PIB has the ability to increase tackiness, to provide water-repellency, to improve viscosity-index, has low gas permeability, provides resistance to chemicals and also provides excellent electrical insulation. PIBs having higher proportion of exo-olefin end groups, i.e., more than 60 mol%, preferably more than 75 mol%, are normally referred to as highly reactive PIBs (HRPIBs). HRPIBs having high levels of terminal olefinic groups are of great commercial importance as they readily undergo chemical reactions. HRPIBs with number-average molecular weight (Mn) of 500 g/mol to 5000 g/mol are of great interest due to their applications as intermediates in the production of the additives for lubricants and fuels, such as surfactants or dispersants. A high proportion of exo-olefin end groups are favored to produce the additives since they have high reactivity in chemically modifications.
Conventional PIBs with low content of exo-olefin end groups (<10 mol%) are produced using water as initiator and a Lewis acid as co initiator, which have low reactivity for further functionalization reactions.
Further, low molecular weight HRPIBs (Mn = 800 g/mol to 2500 g/mol; Mw/Mn~2.0) with more than 80 mol% of exo-olefin end groups are produced conventionally by cationic polymerization of isobutene initiated by Lewis acid based system at temperatures below 0 °C. However, these processes are difficult to handle, and use halogenated solvents, which make the overall reaction expensive.
Therefore, there is felt a need for a process for preparing high reactive polyisobutylene that mitigates the drawbacks mentioned herein above.
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 of the prior art or to at least provide a useful alternative.
An object of the present disclosure is to provide a process for preparing high reactive polyisobutylene.
Another object of the present disclosure is to provide a simple, rapid and economic process for preparing high reactive polyisobutylene.
Still another object of the present disclosure is to provide a process for preparing high reactive polyisobutylene having comparatively high exo-olefin content.
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 producing poly-isobutylene having exo-olefin content of at least 65 mol %. The process comprises providing a feedstock comprising isobutylene monomer. The isobutylene monomer and a catalyst system comprising an ionic liquid and a fluid medium complex is introduced to a reactor and polymerization of isobutylene monomer is initiated under stirring at a temperature in the range of 0 °C to 30 °C to obtain the poly-isobutylene containing exo-olefin content of at least 65 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 the FTIR spectrum of poly-isobutylene polymer obtained by the process of the present disclosure; and
Figures 2a and 2b illustrate the 1H NMR spectra of poly-isobutylene polymer prepared by the process of the present disclosure.
DETAILED DESCRIPTION
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.
High reactive polyisobutylene (HRPIB) is a commercially important chemical, due to its use as a precursor/intermediate in the preparation of motor oil and fuel additives in the automobile industry. HRPIBs have a high amount of double bonds in the terminal position, thereby allowing it to react more quickly. Also, HRPIBs produce less char during manufacture and the derivative products are used to improve the lubricant and fuel performance.
Commercial synthesis of high reactive polyisobutylene (HRPIB) involves the polymerization of isobutylene using complexes of BF3 with alcohols or ethers as co-initiators at temperatures below 0 °C. Maintaining the reactors at this low temperature necessitates the use of dedicated equipments, thereby adding to the overall cost of the process.
The present disclosure envisages a single-step and cost-effective process for preparing highly reactive polyisobutylenes (HRPIBs) with high content of exo-olefin end groups, using a catalyst system comprising ionic liquid and fluid medium.
In an aspect of the present disclosure, there is provided a process for preparing highly reactive polyisobutylenes (HRPIBs) having exo-olefin content of at least 65 mol %. The process comprises cationic polymerization of isobutylene (IB) using a catalyst system comprising an ionic liquid and a fluid medium in a pre-determined ratio. The process is hereinafter described in detail.
Initially, a feedstock comprising isobutylene monomer is provided. Typically, the feedstock is a hydrocarbon. In an embodiment, the feedstock is C4 raffinate containing 10 % to 90 % isobutylene monomer. In a preferred embodiment, the C4 raffinate comprises 20 % to 30 % isobutylene monomer.
A catalyst system comprising an ionic liquid and a fluid medium is then provided. The ionic liquid comprises a Lewis acid and a base.
Ionic liquids are typically organic salts having melting points less than 100 °C, often even lower than room temperature.
Typically, the ionic liquid comprises an adduct or a complex of a Lewis acid and a base in a pre-determined ratio. In accordance with the embodiments of the present disclosure, the ratio of the Lewis acid to the base can be in the range of 1:1 to 5:1. In an exemplary embodiment, the ratio of the Lewis acid to the base is 2:1.
In accordance with the embodiments of the present disclosure, the Lewis acid can be a Group III element containing compound selected from the group consisting of AlCl3, BF3, GaCl3, and FeCl3. The base can be selected from the group consisting of amides, urea and urea derivatives. In an embodiment of the present disclosure, the Lewis acid is aluminum chloride (AlCl3) and the base is urea.
The isobutylene monomer and the catalyst system is introduced into a reactor and polymerization of the isobutylene monomer is carried out under stirring at a temperature in the range of 0 °C to 30 °C to obtain the poly-isobutylene containing exo-olefin content of at least 65 mol %.
The polymerization of isobutylene is carried out under inert atmosphere. The stirring is typically carried out at a speed of rotation in the range of 400 rpm to 600 rpm. In an embodiment, the stirring is carried out at 500 rpm speed.
The process of the present disclosure enables the preparation of high reactive polyisobutylenes having low molecular weight. The HRPIB obtained by the process of the present disclosure has a number average molecular weight in the range of 800 g/mol to 2500 g/mol. The ratio of the weight average molecular weight and the number average molecular weight [Mw/Mn] of the polyisobutylene is typically in the range of 1 to 5. In one embodiment, the ratio of the weight average molecular weight and number average molecular weight [Mw/Mn] is 2.
In accordance with the embodiments of the present disclosure, the polymerization can be a batch process, a continuous process or a semi-continuous process.
In an embodiment of the present disclosure, the polymerization is carried out in the presence of low molecular weight polyisobutylene having a molecular weight in the range of 1000 g/mol to 2500 g/mol. The low molecular weight polyisobutylene aids in seeding or initialization of the polymerization. In an embodiment of the present disclosure, low molecular weight polyisobutylene also helps to aggregate/orient the polymerization.
Typically, the low molecular weight polyisobutylene and the catalyst system can be blended for a time period in the range of 2 minutes to 30 minutes to activate the catalyst. The amount of the low molecular weight polyisobutylene can be in the range of 0.1 wt% to 5 wt% with respect to the amount of the catalyst system. When a low molecular weight polyisobutylene is used during the polymerization, a slurry comprising the catalyst system and low molecular weight polyisobutylene in a pre-determined proportion under inert atmosphere is prepared.
The present disclosure also provides a process for preparing a catalyst system comprising an ionic liquid-fluid medium complex which is used for catalyzing the polymerization of isobutylene to yield the HRPIB. In accordance with the present disclosure, the fluid medium system comprises non-polar fluid medium selected from the group consisting of benzene, toluene, chlorobenzene, cyclohexane, hexane, and dimethylformamide. The ionic liquid-fluid medium system can be prepared by mixing a base with a fluid medium in a reactor under inert atmosphere under stirring for a pre-determined time period. The reactor is typically equipped with an overhead stirrer. Conventionally halogenated (chlorinated) solvents are used, which are expensive and hazardous. However, the present disclosure avoids the use of these halogenated solvents for the preparation of HRPIB. The base can be selected from the group consisting of amides, urea and urea derivatives.
A Lewis acid is then slowly added to the mixture under stirring. After completion of the addition of the Lewis acid, the resultant mass is further stirred for a time period in the range of 2 hours to 5 hours to obtain a slurry comprising the ionic liquid-fluid medium complex. In an embodiment, the inert atmosphere is provided by nitrogen. Typically, the Lewis acid is a Group III element containing compound selected from the group consisting of AlCl3, BF3, GaCl3, and FeCl3. A slurry comprising the catalyst system and optionally the nucleating agent is used for the polymerization of isobutylene.
This is followed by the addition of starting material in the reactor, such as C4 raffinate to initiate the polymerization at a temperature in the range of 0 °C to 30 °C. The C4 raffinate contains the predetermined amount of isobutylene monomer required for the polymerization reaction. Typically, the heat of polymerization is dissipated to maintain the reaction temperature. The reaction is stopped by removing the unreacted material from the reactor. On completion of the polymerization, the HRPIB is isolated and the quantification of the exo-olefin in HRPIB can be confirmed by 1H NMR analysis.
Conventionally, synthesis of HRPIB requires low temperature (-50 °C to 0 °C) and halogenated fluid medium system, which necessitates the use of specialized equipment and thereby increases the overall cost. Further, the halogenated solvents are expensive and are also hazardous. The present disclosure overcomes this limitation by using ionic liquid-fluid medium complex, wherein the ionic liquid is synthesized in the presence of fluid medium forming a complex at ambient temperature, does not require halogenated solvent, has higher productivity and ensures minimal use of catalyst (ionic liquid-fluid medium complex).
The present disclosure provides a simple and single-step process for preparing high reactive polyisobutylene by ionic liquid-fluid medium system that is cost effective, wherein polymerization is initiated at room temperature, and provides high yield of the HRPIB.
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: Preparation of high reactive polyisobutylene in accordance with the present disclosure
Step-Ia: Preparation of Ionic Liquid-fluid medium complex (Urea-AlCl3-benzene) using urea, AlCl3 and benzene:
5 g (0.083 mol) of urea was charged into a reactor under N2 atmosphere and equipped with an overhead stirrer. Then, 6.5 g (7.5 ml) of benzene was added and stirred for 30 minutes. 22.2 g (0.166 mol) of AlCl3 was slowly added under stirring in 30 minutes. After the complete addition of the AlCl3, the whole mass was stirred for 3 hours resulting in the formation of Urea-AlCl3-benzene complex.
Step-Ib: Preparation of Ionic Liquid-fluid medium complex (Urea-AlCl3-toluene) using urea, AlCl3 and toluene:
1 g (0.0166 mol) of urea was charged into a reactor maintained under N2 atmosphere and equipped with an overhead stirrer. Then, 1.5 g (2 ml) of toluene was added and stirred for 30 minutes. 4.5 g (0.0332 mol) of AlCl3 was slowly added under stirring in 30 minutes. After the complete addition of the AlCl3, the whole mass was stirred for 3 hours resulting in the formation of Urea-AlCl3-toluene complex.
Step-II: Synthesis of the polymer (HRPIB):
A slurry with ionic liquid (obtained in Step-I and Step-II) was taken separately. 375 mg based on 0.5% of ionic liquid complex on active monomer and low molecular weight polyisobutylene (approximately 13 equivalent of catalyst) in the reactor under N2 flow was prepared. Then, C4 raffinate (75 g of isobutene content which is 25% in feedback supplied) was introduced in the reactor at 600 rpm agitation to start polymerization at 10 °C. The temperature was maintained using a cooling jacket. The heat of polymerization was dissipated to maintain the reaction temperature at 10 °C. Approximately 74 g HRPIB was obtained after the completion of the polymerization in 2 hours. On completion of the reaction HRPIB was isolated and used for further analysis. The HRPIB obtained using the ionic liquid complex obtained in Step-Ia and Step-Ib is summarized in Table-1 and Table-2, respectively. The FTIR spectrum of poly-isobutene polymer obtained by the process of the present disclosure is illustrated in Figure-1. The 1H NMR spectra of poly-isobutene polymer prepared by the process of the present disclosure and product is illustrated Figure-2a (from Table-1) and Figure-2b (from Table-2), respectively.
Table-1: PIB synthesis using ionic liquid-fluid medium prepared in Step-I
S. No. Isobutylene in C4 Raffinate (g) Catalyst amount (weight % of active monomer) Temp.
(°C) Time
(h) Conversion
(%) Vinylidene end group (%)
1 75 375 mg (0.5%) 10 2 99 72
2. 75 300 mg (0.4%) 10 2 99 75
3. 75 225 mg (0.3%) 10 2 80 76

It is seen from Table-1 that a high content of exo-olefin was obtained when polyisobutylene was prepared using ionic liquid-fluid medium prepared in Step-Ia (AlCl3+Urea+ Benzene) in accordance with the process of the present disclosure.
Table-2: PIB synthesis using ionic liquid-fluid medium prepared in Step-II
S. No. Isobutylene in C4 Raffinate (g) Catalyst amount (weight % of active monomer) Temp.
(°C) Time
(h) Conversion
(%) Vinylidene end group (%)
1 75 375 mg (0.5%) 10 2 93 65
2. 75 300 mg (0.4%) 10 2 80 70
3. 75 225 mg (0.3%) 10 2 70 72

It is seen from Table-2 that a high content of exo-olefin was obtained when polyisobutylene was prepared using ionic liquid-fluid medium complex prepared in Step-Ib (AlCl3+Urea+ Toluene) in accordance with the process of the present disclosure.
It is seen from the 1H NMR spectra that the polyisobutylene obtained by the process of the present disclosure has higher content of exo-olefin (Figure-2a). The expansion of olefinic region (inset) shows two major signals at 4.64 and 4.85 ppm for the terminal vinylidene (exo olefin) end groups. The small fraction of endo-olefin-terminated PIB is observed at 5.15 ppm.
In the IR spectra of the product, strong peaks were observed at 890-900 cm-1 for the higher vinylidene or exo content as depicted by the arrow in Figure-1.
TECHNICAL ADVANCEMENTS
The present disclosure described herein above has several technical advantages including, but not limited to, the realization of a single-step and cost-effective process for preparing high reactive polyisobutylene having high content of exo-olefin.
The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples 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 examples should not be construed as limiting the scope of the embodiments herein.
The foregoing description of the specific embodiments so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.
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 disclosure to achieve one or more of the desired objects or results.
Any discussion of documents, acts, materials, devices, articles or the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.
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.