EP2658897A1 - Amino functionalised oligoimides with enhanced storage stability - Google Patents

Amino functionalised oligoimides with enhanced storage stability

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Publication number
EP2658897A1
EP2658897A1 EP11817412.7A EP11817412A EP2658897A1 EP 2658897 A1 EP2658897 A1 EP 2658897A1 EP 11817412 A EP11817412 A EP 11817412A EP 2658897 A1 EP2658897 A1 EP 2658897A1
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EP
European Patent Office
Prior art keywords
dianhydride
tetracarboxylic dianhydride
anhydride
oligoimide
preparation
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
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EP11817412.7A
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German (de)
French (fr)
Inventor
Mayank Dwivedi
Hari Sarvothama Rao Locanindi
Reddy Krishna Mohan SRINIVASULU
Dhanasekharan Janakiraman
Madhusudana Rao Bevara
Rajesh Kumar SRIPERAMBUDUR
Ponrathnam Surendra
Raman Rajan Chelanattukizhakkemadath
Kumar Tayal Rajiv
Mohammed Shadbar Qureshi
Nayaku Nivrati Chavan
Sarika Babasaheb Deokar
Khudbudin Baban Mulani
Ravindra Vasant Ghorpade
Sunil Sitaram Bhongale
Archana Chetan Nalawade
Kalpana Vishwanathrao Sontakke
Sonali Madhavrao Bhosle
Smita Atmaram Mule
Deepa Arun Dhoble
Aruldoss John
Wasif Abdul Lateef Shaikh
Reghunathan Harikrishna
Vellimalai Punitharasu
Mohasin Shamshuddin MOMIN
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Director General Defence Research & Development Organisation
Director General Defence Res and Dev Organization Ministry of Defence Government of India
Original Assignee
Director General Defence Research & Development Organisation
Director General Defence Res and Dev Organization Ministry of Defence Government of India
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Application filed by Director General Defence Research & Development Organisation, Director General Defence Res and Dev Organization Ministry of Defence Government of India filed Critical Director General Defence Research & Development Organisation
Publication of EP2658897A1 publication Critical patent/EP2658897A1/en
Ceased legal-status Critical Current

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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G73/00—Macromolecular compounds obtained by reactions forming a linkage containing nitrogen with or without oxygen or carbon in the main chain of the macromolecule, not provided for in groups C08G12/00 - C08G71/00
    • C08G73/06—Polycondensates having nitrogen-containing heterocyclic rings in the main chain of the macromolecule
    • C08G73/10—Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors
    • C08G73/1003—Preparatory processes
    • C08G73/1007—Preparatory processes from tetracarboxylic acids or derivatives and diamines
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G73/00—Macromolecular compounds obtained by reactions forming a linkage containing nitrogen with or without oxygen or carbon in the main chain of the macromolecule, not provided for in groups C08G12/00 - C08G71/00
    • C08G73/06—Polycondensates having nitrogen-containing heterocyclic rings in the main chain of the macromolecule
    • C08G73/10—Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors
    • C08G73/1003—Preparatory processes
    • C08G73/1007—Preparatory processes from tetracarboxylic acids or derivatives and diamines
    • C08G73/1028—Preparatory processes from tetracarboxylic acids or derivatives and diamines characterised by the process itself, e.g. steps, continuous
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G73/00—Macromolecular compounds obtained by reactions forming a linkage containing nitrogen with or without oxygen or carbon in the main chain of the macromolecule, not provided for in groups C08G12/00 - C08G71/00
    • C08G73/06—Polycondensates having nitrogen-containing heterocyclic rings in the main chain of the macromolecule
    • C08G73/10—Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors
    • C08G73/1003—Preparatory processes
    • C08G73/1007—Preparatory processes from tetracarboxylic acids or derivatives and diamines
    • C08G73/1028—Preparatory processes from tetracarboxylic acids or derivatives and diamines characterised by the process itself, e.g. steps, continuous
    • C08G73/1032—Preparatory processes from tetracarboxylic acids or derivatives and diamines characterised by the process itself, e.g. steps, continuous characterised by the solvent(s) used
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G73/00—Macromolecular compounds obtained by reactions forming a linkage containing nitrogen with or without oxygen or carbon in the main chain of the macromolecule, not provided for in groups C08G12/00 - C08G71/00
    • C08G73/06—Polycondensates having nitrogen-containing heterocyclic rings in the main chain of the macromolecule
    • C08G73/10—Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors
    • C08G73/1046—Polyimides containing oxygen in the form of ether bonds in the main chain
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G73/00—Macromolecular compounds obtained by reactions forming a linkage containing nitrogen with or without oxygen or carbon in the main chain of the macromolecule, not provided for in groups C08G12/00 - C08G71/00
    • C08G73/06—Polycondensates having nitrogen-containing heterocyclic rings in the main chain of the macromolecule
    • C08G73/10—Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors
    • C08G73/1067—Wholly aromatic polyimides, i.e. having both tetracarboxylic and diamino moieties aromatically bound
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G73/00—Macromolecular compounds obtained by reactions forming a linkage containing nitrogen with or without oxygen or carbon in the main chain of the macromolecule, not provided for in groups C08G12/00 - C08G71/00
    • C08G73/06—Polycondensates having nitrogen-containing heterocyclic rings in the main chain of the macromolecule
    • C08G73/10—Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors
    • C08G73/1067—Wholly aromatic polyimides, i.e. having both tetracarboxylic and diamino moieties aromatically bound
    • C08G73/1071—Wholly aromatic polyimides containing oxygen in the form of ether bonds in the main chain
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L79/00—Compositions of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing nitrogen with or without oxygen or carbon only, not provided for in groups C08L61/00 - C08L77/00
    • C08L79/04—Polycondensates having nitrogen-containing heterocyclic rings in the main chain; Polyhydrazides; Polyamide acids or similar polyimide precursors
    • C08L79/08—Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors

Definitions

  • the present invention relates to an improved process for the preparation of amino functionalized oligomeric monomeric reactant type polyimides having higher stability. More particularly it relates to a process for the preparation of soluble imide prepolymers, used as matrix resins that can be rapidly cured with multi-functional moieties such as diepoxy, dicarboxyl, anhydride, diisocyanates to form crosslinked structures having enhanced thermal stability and mechanical strength.
  • Oligoimides as a class of materials are well known and are used widely. It is also well documented that these materials have several shortcomings which makes it difficult to harness their usefulness. Since, aliphatic polyimides are class of polymers known hitherto have relatively poor thermo-oxidative stability, whereas, aromatic types are much preferred for applications requiring the best possible resistance to thermo-oxidative degradation. Some of the areas of applications of these materials are in the areas of high performance composite materials and aerospace applications.
  • aromatic polyimides a class of high performance polymers because of their excellent properties such as heat, thermal stability and good mechanical and electrical properties. Yet the aromatic polyimides are extremely difficult to process due to their insolubility and extremely high softening points or melting points. Hence, fabrication was not possible from melt. For the injection and extrusion moulding conventional aromatic polyimides did not show suitable flow properties and therefore special fabrication methods such as compression or sintering moulding had to be used. The structural rigidity of the polymer backbone, due to aromatic rings, made these materials insoluble in organic solvents.
  • the first is a two step method for synthesis of polyimide via polyamic acid route was disclosed (U.S. Pat. No.3,624,050 and U.S. Pat. No.6,852,826). It involved reacting a dianhydride and a diamine at ambient conditions in presence or absence of dipolar aprotic solvent such as N, N-dimethyl acetamide (DMAc) or N-methyl pyrrolidone (NMP) to yield the corresponding polyamic acid, amic ester or polyamic acid ester which was then cyclised into final polyimide through thermal treatment or chemical dehydration wherein the amide nitrogen attacks the adjacent carbonyl carbon resulting in elimination of water or alcohol molecules.
  • dipolar aprotic solvent such as N, N-dimethyl acetamide (DMAc) or N-methyl pyrrolidone (NMP)
  • Non-melting condensation polymers are based on pyromellitic dianhydride, 3, 3', 4, 4' benzophenone tetracarboxylic dianhydride and aromatic amines such as oxydianiline.
  • the reaction is carried out below 50°C in presence of polar solvents to form the polyamic acid.
  • the low temperature prevents cyclisation and retains solubility and hence processibility.
  • This material is then moulded under pressure by heat treatment in the range of 200-300°C for imidisation to be completed.
  • These intrinsically thermoset resins can be transformed into thermoplastic polyimides by modification of the polymer chains to improve processibility.
  • Addition polyimides are best defined as low molecular weight, at least dysfunctional monomers or prepolymers or mixtures thereof that carry functional reactive terminations and imide functions on their backbone.
  • the reactive end groups can undergo homo- and/or copolymerisation by thermal or catalytic means.
  • the addition polyimide can be synthesized via the classical route of reacting the tetracarboxylic dianhydride and the diamine in the presence of a monofunctional endcapper.
  • the endcapper carries a functional group susceptible to polymerization, copolymerization or crosslinking.
  • addition polyimides are classified by the chemical nature of their reactive endgroups.
  • an imide oligomer containing maleimide endgroups is described as a "Maleimide-Resin".
  • the molecular weight and the molecular weight distribution of the imide backbone can be tailored in the usual way via the stoichiometry of the tetracarboxylic dianhydride, the aromatic diamine as well as the synthetic conditions.
  • the end groups generally used have been norbornene, (U.S. Patent. No. 5,708, 127) maleimide, acetylenic, (U.S. Pat. No.4,299,750) allylnadic and benzocyclobutene.
  • US 5464927 discloses a process for radiation sensitive polyimides.
  • the process of formation of the polymer mentioned is the direct reaction of dianhydride and diamine.
  • the polyamic acid by this direct reaction is unstable and undergoes molecular equilibriation.
  • the polyimide formed by this process has high molecular weight.
  • Mercado et al. (SPIE Proceedings, 2004) describes reaction of dianhydride with diamine at 25 °C in NN-dimethyl acetamide for 24 hours followed by heating at 160 °C for 24 hours in presence of toluene to give high molecular weight polyimide. It also disclose a reaction of dianhydride with excess of alcohol to form the ester acid. The excess alcohol is distilled off and then reacted with diamine at 190 °C.
  • Polyamic acid is relatively unstable at or above ambient temperature because of molecular rearrangements due to equilibration. The most detrimental reaction is due to the hydrolytic instability of the amide bonds located at ortho positions to the carboxylic acid units. Even at room temperature some dehydrocyclisation occurs, producing imide rings and water followed by hydrolysis of amide groups resulting in low molecular weight polymers. Alkyl esters were introduced as ortho substituents to overcome the effect of this hydrolysis leading to imide formation.
  • the first path consists of reaction of dianhydride with alcohol such as methyl, ethyl, isopropyl to form the corresponding half esters that are further reacted with amine to form polyamic acid and cured at 350°C to 400°C.
  • the present inventors have surprisingly developed a novel, convenient and efficient process for the preparation of soluble imide prepolymers which can be cured with multi-functional moieties such as diepoxy, dicarboxyl, anhydride, diisocyanates to form crosslinked structures having enhanced thermal stability and mechanical strength and which has enhanced storage stability.
  • multi-functional moieties such as diepoxy, dicarboxyl, anhydride, diisocyanates
  • the present inventors have found that the use of higher alcohols in the process of present invention enhances the storage stability of the amino functionalised oligoimides and if lower alcohols are used in the process of the present invention the rate of imidization at room temperature increases as a result processing of the material becomes difficult.
  • the present inventors have found that the inherent weakness while using methyl and ethyl ester formed by the use of lower alcohol is that amidization and imidization processes are faster at room temperature. Due to this quick aging, the prepegs expire with limited shelf-life within one to three weeks at room temperature. The present inventors have found that the reason for increase in longer shelf-life is due to large isopropyl ester groups formed due the use of higher alcohol like isopropyl alcohol compared to the methyl ester/ethyl ester group. The isopropyl is a bulkier and poorer leaving group and consequently should slow the reactions between the monomers in solutions and prepregs by slowing the rate determining step in aging process.
  • the present inventors have developed a process wherein ester is formed in situ and is further reacted with diamine directly without isolating the intermediate product as there is a difficulty in isolation of the diester diacid as strong hydrogen bonds are formed between excess alcohol and the acid group of the diester diacid. Hence, it is difficult to get a solid free flowing product that can be further reacted with diamine.
  • the present inventors have developed a process wherein the reaction with diamine can carried out at room temperature which avoids reaction at elevated temperature.
  • a process for the preparation of amino functionalized oligoimide Telechelics comprising the steps of: i Reacting dianhydride and higher alcohol to obtain diacid-diester;
  • step (i) Contacting in an inert atmosphere the product obtained in step (i) with polar aprotic solvents at a temperature in the range of 25 °C to 80 °C for a period of 2 to 64 hours with agitation;
  • step (iii) Adding Diamine to the solution obtained in step (ii) followed by stirring the reaction mixture vigorously for a period in the range of 2 to 6 hours in the temperature range of 25 °C to 80 °C to obtain Polyamic ester;
  • the aim of the present invention is to provide a process for the preparation of amino functionalized polymeric monomeric reactant type polyimides materials that have an increased shelf-life and offer advantages of solubility, ease in processing and result in materials with good mechanical and thermal properties.
  • the invention relates to a process for the preparation of amino functionalized polymeric monomeric reactant type polyimides which has improved room temperature storage stability, without adversely affecting the processibility of the polyimide composites.
  • the soluble imide prepolymers can be used as matrix resins that can be rapidly cured to form stable polyimides, analogous to polymeric monomeric reactants (PMR) type polyimides. These resins are characterized by structures having amine functional end groups. The amine functionality of the cured resin can be further reacted with other different multi-functional moieties such as diepoxy, dicarboxyl, anhydride, diisocyanates to form crosslinked structures having enhanced thermal stability and mechanical strength.
  • the polymers prepared by the process of this invention can be used as materials in advanced composites having high temperature stability.
  • the present invention provides a process for the preparation of amino functionalized oligoimide telechelics, which comprise of contacting in an inert atmosphere the product of the reaction between dianhydride and alcohol in a combination with polar aprotic solvents at a temperature in the range of 25 °C to 80 °C for a period of 2 to 64 hours with agitation followed by addition of diamines and stirring vigorously the reaction mixture for a period in the range of 2 to 6 hours in the temperature range of 25 °C to 80 °C followed by collection of the resultant material.
  • the reaction is carried out in two steps.
  • the reaction of dianhydride with alcohol is done in the temperature range of 25 °C to 80 °C for 2 to 64 hours and after diacid diester formation, the amines are added and the stirring is continued at room temperature (25°C).
  • reaction temperature At 25°C required reaction time is 64 hours and at 80°C required reaction time is 2 hours only. Addition of diamine, followed by stirring is done at room temperature (25°C) only and not at elevated temperature.
  • Higher alcohol is defined herein to include alcohols having a higher molecular weight than Methanol and Ethanol.
  • step (i) Contacting in an inert atmosphere the product obtained in step (i) with polar aprotic solvents at a temperature in the range of 25 °C to 80 °C for a period of 2 to 64 hours with agitation;
  • step (iii) Adding Diamine to the solution obtained in step (ii) followed by stirring vigorously the reaction mixture for a period in the range of 2 to 6 hours in the temperature range of 25 °C to 80 °C to obtained Polyamic ester;
  • step (iii) is further cured to obtained compound of formula I.
  • the reaction for synthesizing Oligoimide (Compound of Formula I) by the process of present invention can be represented by scheme I as follows.
  • the higher alcohol used is selected from the group consisting isopropyl alcohol, n-butyl alcohol, t-butyl alcohol, cyclohexanol.
  • the dianhydride used may be chosen from 1 ,2,4,5-benzene tetracarboxylic acid dianhydride, 2,3,4,5-thiophene tetracarboxylic acid dianhydride, 2,3,5,6-pyrazine tetracarboxylic aid dianhydride, 2,3,3',4'-benzophenone tetracarboxylic dianhydride, 2,2',3,3'-benzophenone tetracarboxylic dianhydride, 3,3',4,4 -benzophenone tetracarboxylic dianhydride, pyromellitic dianhydride, 2,3,3',4'- biphenyltetracarboxylic dianhydride, 3,3',4,4'- biphenyl tetracarboxylic dianhydride, anhydrides that can be used are 2,3,3',4'- benzophenone tetracarboxylic dianhydride, 2,3,4,5-thiophene
  • the diamine used is selected from the group consisting m-phenylene diamine, p- phenylene diamine, 3,3'- oxydianiline, 4,4 -oxydianiline, 3,4'-oxydianiline, 4,4'-diaminodiphenyl methane, 3.4'- diaminodiphenyl methane, 4,4'diamino diphenyl propane, 4,4'-diamino benzophenone, 3,3'-diamino benzophenone, m-xylenediamine, p-xylenediamine, 4,4'-diaminodiphenyl sulfone, benzidine, 3,3'-dimethoxy benzidine dihydrochloride, 2,2'-dimethyl benzidine, 3,3'-dimethyl benzidine, 4,4'-diaminobiphenyl, 4,4'- diaminobenzophenone, 4,4'-di
  • the aprotic solvents used is selected from the group consisting dimethyl sulfoxide, dimethyl formamide, dioxane, N-methyl-2-pyrrolidone, N, N'-dimethyl acetamide, N-cyclohexyl-2-pyrrolidone, ionic liquids.
  • the inert gas used is selected from the group consisting nitrogen or argon.
  • an oligoimide (compound of Formula I) having an improved shelf-life of 3 months when stored at room temperature.
  • Formulations were prepared by varying the solid content from 60 % to 80 % of the total composition.
  • the anhydride to amine ratio was also varied ranging from 1 : 1.05 up to 1 .0: 2.0.
  • the formulations were prepared by varying the amine ratio from 10: 90 up to 90: 10.
  • the formulations were prepared by using different alcohols like isopropyl, n-butyl alcohol, t-butyl alcohol and cyclohexanol.
  • the compositions were prepared by insitu esterification of the anhydride at elevated temperature followed by addition of amine or mixture of amines at ambient temperatures.

Abstract

The invention relates to an improved process for the preparation of amino functionalized oligomeric monomeric reactant type polyimides having higher stability. More particularly it relates to a process for the preparation of soluble imide prepolymers, used as matrix resins that can be rapidly cured with multi-functional moieties such as diepoxy, dicarboxyl, anhydride, diisocyanates to form crosslinked structures having enhanced thermal stability and mechanical strength.

Description

AMINO FUNCTIONALISED OLIGOIMIDES WITH ENHANCED
STORAGE STABILITY
FIELD OF INVENTION
The present invention relates to an improved process for the preparation of amino functionalized oligomeric monomeric reactant type polyimides having higher stability. More particularly it relates to a process for the preparation of soluble imide prepolymers, used as matrix resins that can be rapidly cured with multi-functional moieties such as diepoxy, dicarboxyl, anhydride, diisocyanates to form crosslinked structures having enhanced thermal stability and mechanical strength.
BACKGROUND OF THE INVENTION
Oligoimides as a class of materials are well known and are used widely. It is also well documented that these materials have several shortcomings which makes it difficult to harness their usefulness. Since, aliphatic polyimides are class of polymers known hitherto have relatively poor thermo-oxidative stability, whereas, aromatic types are much preferred for applications requiring the best possible resistance to thermo-oxidative degradation. Some of the areas of applications of these materials are in the areas of high performance composite materials and aerospace applications.
Extensive research has been carried out since early 1960s on aromatic polyimides, a class of high performance polymers because of their excellent properties such as heat, thermal stability and good mechanical and electrical properties. Yet the aromatic polyimides are extremely difficult to process due to their insolubility and extremely high softening points or melting points. Hence, fabrication was not possible from melt. For the injection and extrusion moulding conventional aromatic polyimides did not show suitable flow properties and therefore special fabrication methods such as compression or sintering moulding had to be used. The structural rigidity of the polymer backbone, due to aromatic rings, made these materials insoluble in organic solvents. Early attempts to depress the softening temperatures of aromatic polyimides usually involved the substitution of aliphatic segments into the otherwise aromatic polymers to lower the softening points, but this generally resulted in an accompanying decrease in thermo-oxidative stability of the modified > polyimide (U.S. Pat. No. 3,424,718 issued Jan. 28, 1969, to R. J. Angelo for Copolymers of Aromatic Tetracarboxylic Acids with at least Two Organic Diamines).
It is known in the literature that Polyimides can be synthesized by 3 different strategies.
a) Condensation polymers - non melting and thermoplastic,
b) Addition thermoset polymers
c) Hybrid polymers.
The first is a two step method for synthesis of polyimide via polyamic acid route was disclosed (U.S. Pat. No.3,624,050 and U.S. Pat. No.6,852,826). It involved reacting a dianhydride and a diamine at ambient conditions in presence or absence of dipolar aprotic solvent such as N, N-dimethyl acetamide (DMAc) or N-methyl pyrrolidone (NMP) to yield the corresponding polyamic acid, amic ester or polyamic acid ester which was then cyclised into final polyimide through thermal treatment or chemical dehydration wherein the amide nitrogen attacks the adjacent carbonyl carbon resulting in elimination of water or alcohol molecules.
Non-melting condensation polymers are based on pyromellitic dianhydride, 3, 3', 4, 4' benzophenone tetracarboxylic dianhydride and aromatic amines such as oxydianiline. The reaction is carried out below 50°C in presence of polar solvents to form the polyamic acid. The low temperature prevents cyclisation and retains solubility and hence processibility. This material is then moulded under pressure by heat treatment in the range of 200-300°C for imidisation to be completed. These intrinsically thermoset resins can be transformed into thermoplastic polyimides by modification of the polymer chains to improve processibility. There are reports on the use of ester derivatives of the tetracarboxylic acids, rather than dianhydride derivatives, to react with a single aromatic diamine, but while the precursor mixture was thermoplastic at low molecular weights, the high molecular weight polyimides could not be successfully molded even at high temperatures and pressures (U.S. Pat. No. 3,506,583 issued Apr. 4, 1970, to William R. Boram and Luis Acle, Jr., for Monomeric Solid State Solutions of Certain Aromatic Diamines in Derivatives of Benzophenone Tetracarboxylic Acid).
A further development of that approach involved the use of two or more diamines in the reaction with an esterified derivative of 3, 3', 4, 4'-benzophenone tetracarboxylic acid, such that a copolyimide resulted (U.S. Pat. No. 3,726,834 issued Apr. 10, 1973, to Luis Acle, Jr., for Thermoplastic Copolyimides). Although meta-oriented aromatic diamines were used in the formation of the copolyimide precursors, the beneficial effects related to the thermoplasticity of the polymers was ascribed to the random distribution of the mesomers (repeat units) in the polymer chain, the said randomness serving to reduce the degree of crystallinity in the copolyimides in contrast to that of the homopolyimides.
Addition polyimides are best defined as low molecular weight, at least dysfunctional monomers or prepolymers or mixtures thereof that carry functional reactive terminations and imide functions on their backbone. The reactive end groups can undergo homo- and/or copolymerisation by thermal or catalytic means. According to the general definition, the addition polyimide can be synthesized via the classical route of reacting the tetracarboxylic dianhydride and the diamine in the presence of a monofunctional endcapper. The endcapper carries a functional group susceptible to polymerization, copolymerization or crosslinking.
Accordingly, addition polyimides (thermosetting polyimides) are classified by the chemical nature of their reactive endgroups. For example, an imide oligomer containing maleimide endgroups is described as a "Maleimide-Resin". The molecular weight and the molecular weight distribution of the imide backbone can be tailored in the usual way via the stoichiometry of the tetracarboxylic dianhydride, the aromatic diamine as well as the synthetic conditions. The end groups generally used have been norbornene, (U.S. Patent. No. 5,708, 127) maleimide, acetylenic, (U.S. Pat. No.4,299,750) allylnadic and benzocyclobutene. In this case the prepolymer can be processed from a mixture of monomeric reactants using lower (primary) alcohols to esterify an anhydride endcap and an aromatic dianhydride. These monomeric reactants when combined with an aromatic diamine in the molar ratio of N diester- diacid/N+1 diamine/2 ester-acid endcap, form a monomeric mixture which at high temperature is melted and allowed to flow where it subsequently crosslinks by pyrolytic polymerization of unsaturated end groups at around 300°C. This may be a reverse Diels-Alder reaction with cyclopentadiene being released from the norbornene ring followed by its simultaneous polymerization with the maleimide ring formation or complete cure without release, when high enough pressure is applied.
US 5464927 discloses a process for radiation sensitive polyimides. The process of formation of the polymer mentioned is the direct reaction of dianhydride and diamine. The polyamic acid by this direct reaction is unstable and undergoes molecular equilibriation. The polyimide formed by this process has high molecular weight.
Rhee et al. (Macromolecules, 1993) describe three schemes for preparing high molecular weight polyimides by reacting sequentially dianhydride with isopropyl alcohol to form diacid diethyl ester followed by reaction with stoichiometrically equivalent amount of diamine. Such polyimides will have very high molecular weight but will not have definite end functionality for further reaction.
Mercado et al. (SPIE Proceedings, 2004) describes reaction of dianhydride with diamine at 25 °C in NN-dimethyl acetamide for 24 hours followed by heating at 160 °C for 24 hours in presence of toluene to give high molecular weight polyimide. It also disclose a reaction of dianhydride with excess of alcohol to form the ester acid. The excess alcohol is distilled off and then reacted with diamine at 190 °C.
An attempt to improve the room temperature storage stability of the PMR monomer without adversely affecting the processibility of the polyimide composites by the use of higher (secondary) C3 to C5 alcohol is disclosed in U.S. Pat. No. 6,103,864. It further discloses that the use of lower alcohols like methanol, ethanol generates highly toxic volatiles in the manufacturing process as well as during applications. Thermoplastic polyimides are obtained by introducing large cyclic side groups into the polymer chain by tailoring random sequences into the chain or by the interposition of flexible, aliphatic linking groups between the aromatic and heterocyclic moieties. The solubility and fusibility of these polymers are governed by the nature of the cyclic side group and the imide reaction of the chain.
Polyamic acid is relatively unstable at or above ambient temperature because of molecular rearrangements due to equilibration. The most detrimental reaction is due to the hydrolytic instability of the amide bonds located at ortho positions to the carboxylic acid units. Even at room temperature some dehydrocyclisation occurs, producing imide rings and water followed by hydrolysis of amide groups resulting in low molecular weight polymers. Alkyl esters were introduced as ortho substituents to overcome the effect of this hydrolysis leading to imide formation. The first path consists of reaction of dianhydride with alcohol such as methyl, ethyl, isopropyl to form the corresponding half esters that are further reacted with amine to form polyamic acid and cured at 350°C to 400°C.
The disadvantages of polyimides for use in high performance composites or aerospace applications are limitations posed by extreme difficulty to process these materials due to their insolubility as a result of the aromatic rings and extremely high softening points or melting points making fabrication of components impossible from melt.
Some of the above limitations could be overcome by variation in structural entity within the polymer. It is known the structural entity that imparts outstanding thermal and oxidative stability is the imide group. A combination of the imide with aromatic building blocks would result in a polymer with high glass transition temperature and good oxidative stability.
Figure 1
Prior art methods as described above suffer from processing limitations coupled with storage and high temperature stability.
The present inventors have surprisingly developed a novel, convenient and efficient process for the preparation of soluble imide prepolymers which can be cured with multi-functional moieties such as diepoxy, dicarboxyl, anhydride, diisocyanates to form crosslinked structures having enhanced thermal stability and mechanical strength and which has enhanced storage stability. The present inventors have found that the use of higher alcohols in the process of present invention enhances the storage stability of the amino functionalised oligoimides and if lower alcohols are used in the process of the present invention the rate of imidization at room temperature increases as a result processing of the material becomes difficult.
The present inventors have found that the inherent weakness while using methyl and ethyl ester formed by the use of lower alcohol is that amidization and imidization processes are faster at room temperature. Due to this quick aging, the prepegs expire with limited shelf-life within one to three weeks at room temperature. The present inventors have found that the reason for increase in longer shelf-life is due to large isopropyl ester groups formed due the use of higher alcohol like isopropyl alcohol compared to the methyl ester/ethyl ester group. The isopropyl is a bulkier and poorer leaving group and consequently should slow the reactions between the monomers in solutions and prepregs by slowing the rate determining step in aging process.
The present inventors have developed a process wherein ester is formed in situ and is further reacted with diamine directly without isolating the intermediate product as there is a difficulty in isolation of the diester diacid as strong hydrogen bonds are formed between excess alcohol and the acid group of the diester diacid. Hence, it is difficult to get a solid free flowing product that can be further reacted with diamine. The present inventors have developed a process wherein the reaction with diamine can carried out at room temperature which avoids reaction at elevated temperature.
OBJECT OF THE INVENTION
It is the object of the present invention to provide a novel process for the preparation of soluble imide prepolymers which be cured with multi-functional moieties such as diepoxy, dicarboxyl, anhydride, diisocyanates to form crosslinked structures having enhanced thermal stability and mechanical strength and which has enhanced storage stability. It is another object of the present invention to improve the room temperature storage stability of the monomer solutions by the use of higher alcohol without adversely affecting the processibility of the polyimide composites.
It is yet another object of the present invention to provide a process which avoids generation of highly toxic volatiles. SUMMARY OF INVENTION
According to an aspect of the present invention there is provided a process for the preparation of amino functionalized oligoimide Telechelics comprising the steps of: i Reacting dianhydride and higher alcohol to obtain diacid-diester;
ii Contacting in an inert atmosphere the product obtained in step (i) with polar aprotic solvents at a temperature in the range of 25 °C to 80 °C for a period of 2 to 64 hours with agitation;
iii Adding Diamine to the solution obtained in step (ii) followed by stirring the reaction mixture vigorously for a period in the range of 2 to 6 hours in the temperature range of 25 °C to 80 °C to obtain Polyamic ester;
iv Curing the compound of step (iii) to obtain compound of formula I.
DETAILED DESCRIPTION OF THE INVENTION
The aim of the present invention is to provide a process for the preparation of amino functionalized polymeric monomeric reactant type polyimides materials that have an increased shelf-life and offer advantages of solubility, ease in processing and result in materials with good mechanical and thermal properties.
The invention relates to a process for the preparation of amino functionalized polymeric monomeric reactant type polyimides which has improved room temperature storage stability, without adversely affecting the processibility of the polyimide composites. The soluble imide prepolymers can be used as matrix resins that can be rapidly cured to form stable polyimides, analogous to polymeric monomeric reactants (PMR) type polyimides. These resins are characterized by structures having amine functional end groups. The amine functionality of the cured resin can be further reacted with other different multi-functional moieties such as diepoxy, dicarboxyl, anhydride, diisocyanates to form crosslinked structures having enhanced thermal stability and mechanical strength. The polymers prepared by the process of this invention can be used as materials in advanced composites having high temperature stability.
The present invention provides a process for the preparation of amino functionalized oligoimide telechelics, which comprise of contacting in an inert atmosphere the product of the reaction between dianhydride and alcohol in a combination with polar aprotic solvents at a temperature in the range of 25 °C to 80 °C for a period of 2 to 64 hours with agitation followed by addition of diamines and stirring vigorously the reaction mixture for a period in the range of 2 to 6 hours in the temperature range of 25 °C to 80 °C followed by collection of the resultant material.
The reaction is carried out in two steps. The reaction of dianhydride with alcohol is done in the temperature range of 25 °C to 80 °C for 2 to 64 hours and after diacid diester formation, the amines are added and the stirring is continued at room temperature (25°C).
The time period required for a particular reaction depend upon reaction temperature. At 25°C required reaction time is 64 hours and at 80°C required reaction time is 2 hours only. Addition of diamine, followed by stirring is done at room temperature (25°C) only and not at elevated temperature.
In the process of the present invention, wherein in situ ester is formed and is further reacted with diamine directly without isolating the intermediate product. There is a difficulty in isolation of the diester diacid as strong hydrogen bonds are formed between excess alcohol and the acid group of the diester diacid. Hence, it is difficult to get a solid free flowing product that can be further reacted with diamine. In the present invention the reaction with diamine is carried out at room temperature while in prior art it is reacted at elevated temperature. In the process of the present invention higher alcohols is used which enhances the storage stability of the amino functionalised oligoimides and if lower alcohols are used in the process of the present invention the rate of imidization at room temperature increases as a result processing of the material becomes difficult.
The inherent weakness while using methyl and ethyl ester formed due to the use of lower alcohol is that amidization and imidization processes are faster at room temperature. Due to this quick aging, the prepegs expire with limited shelf-life within one to three weeks at room temperature. The reason for increase in longer shelf-life is due to large isopropyl ester groups formed by the use of higher alcohol group compared to the methyl ester/ethyl ester group. The isopropyl is a bulkier and poorer leaving group and consequently should slow the reactions between the monomers in solutions and prepregs by slowing the rate determining step in aging process.
"Higher alcohol" is defined herein to include alcohols having a higher molecular weight than Methanol and Ethanol.
In an embodiment of the present invention provides a process for the synthesis of Oligoimide (Compound of Formula I) comprising the steps of:
i Reacting dianhydride and higher alcohol to obtain diacid-diester;
ii Contacting in an inert atmosphere the product obtained in step (i) with polar aprotic solvents at a temperature in the range of 25 °C to 80 °C for a period of 2 to 64 hours with agitation;
iii Adding Diamine to the solution obtained in step (ii) followed by stirring vigorously the reaction mixture for a period in the range of 2 to 6 hours in the temperature range of 25 °C to 80 °C to obtained Polyamic ester;
iv The compound obtained in step (iii) is further cured to obtained compound of formula I. The reaction for synthesizing Oligoimide (Compound of Formula I) by the process of present invention can be represented by scheme I as follows.
Oligoimides
Formula I
In an embodiment of the present invention the higher alcohol used is selected from the group consisting isopropyl alcohol, n-butyl alcohol, t-butyl alcohol, cyclohexanol.
In an embodiment of the present invention, the dianhydride used may be chosen from 1 ,2,4,5-benzene tetracarboxylic acid dianhydride, 2,3,4,5-thiophene tetracarboxylic acid dianhydride, 2,3,5,6-pyrazine tetracarboxylic aid dianhydride, 2,3,3',4'-benzophenone tetracarboxylic dianhydride, 2,2',3,3'-benzophenone tetracarboxylic dianhydride, 3,3',4,4 -benzophenone tetracarboxylic dianhydride, pyromellitic dianhydride, 2,3,3',4'- biphenyltetracarboxylic dianhydride, 3,3',4,4'- biphenyl tetracarboxylic dianhydride, anhydrides that can be used are 2,3,3',4'- benzophenone tetracarboxylic dianhydride, 2, 2', 3, 3'- benzophenone tetracarboxylic dianhydride, 1 ,4,5,8-naphthalene tetracarboxylic dianhydride, perylene-3,4,9,10- tetracarboxylic dianhydride, 4,4'-oxydiphthalic anhydride, 3,3'-oxydiphthalic anhydride, 4,4'-(hexafluoro isopropylidine) diphthalic anhydride, 4,4'-isopropylidene diphthalic anhydride, 3,4'-isopropylidene diphthalic anhydride, 3,3'-isopropylidene diphthalic anhydride, 4,4'-sulphonyl diphthalic anhydride, 4,4 -methylene diphthalic anhydride, 4,4'thiodiphthalic anhydride, 4,4'-ethylidene diphthalic anhydride, phenyl trifluoroethylidene diphthalic anhydride, 2,3,6,7-naphthalene tetracarboxylic dianhydride, 1 , 2, 5,6-naphthalene tetracarboxylic dianhydride, and such like. In yet another embodiment of the present invention the diamine used is selected from the group consisting m-phenylene diamine, p- phenylene diamine, 3,3'- oxydianiline, 4,4 -oxydianiline, 3,4'-oxydianiline, 4,4'-diaminodiphenyl methane, 3.4'- diaminodiphenyl methane, 4,4'diamino diphenyl propane, 4,4'-diamino benzophenone, 3,3'-diamino benzophenone, m-xylenediamine, p-xylenediamine, 4,4'-diaminodiphenyl sulfone, benzidine, 3,3'-dimethoxy benzidine dihydrochloride, 2,2'-dimethyl benzidine, 3,3'-dimethyl benzidine, 4,4'-diaminobiphenyl, 4,4'- diaminobenzophenone, 4,4'-diamino benzanilide either alone or their combinations.
In yet another embodiment of the present invention the aprotic solvents used is selected from the group consisting dimethyl sulfoxide, dimethyl formamide, dioxane, N-methyl-2-pyrrolidone, N, N'-dimethyl acetamide, N-cyclohexyl-2-pyrrolidone, ionic liquids.
In yet another embodiment the inert gas used is selected from the group consisting nitrogen or argon.
In further embodiment of the present invention there is provided an oligoimide (compound of Formula I) having an improved shelf-life of 3 months when stored at room temperature.
The process of the present invention is described herein below with reference to the following examples, which are only illustrative in nature and should not be construed to limit the scope of the invention in any manner. EXAMPLES
Formulations were prepared by varying the solid content from 60 % to 80 % of the total composition. The anhydride to amine ratio was also varied ranging from 1 : 1.05 up to 1 .0: 2.0. In case of mixture of amines used the formulations were prepared by varying the amine ratio from 10: 90 up to 90: 10. The formulations were prepared by using different alcohols like isopropyl, n-butyl alcohol, t-butyl alcohol and cyclohexanol. The compositions were prepared by insitu esterification of the anhydride at elevated temperature followed by addition of amine or mixture of amines at ambient temperatures.
Example 1
To a dry 50 ml_ round bottom flask equipped with magnetic stirrer, 3.3308 g (0.01034 mol) of 3, 3', 4, 4'-benzophenone tetracarboxylic dianhydride (BTDA) was added. Then 4.2425 g (0.07059 mol) of isopropyl alcohol and 1 g mixture of N- methyl-2-pyrrolidone and N, N'-dimethyl acetamide were added to the flask. The reaction mixture was refluxed for 2 hours with stirring under the nitrogen atmosphere. After 2 hours, the solution was cooled to ambient temperature. After cooling the solution 1 .1 150 g (0.01031 mol) of m-phenylenediamine and 0.31 17 g (0.00156 mol) of 4, 4'-oxydianiline were added and reaction mixture was thoroughly mixed on magnetic stirrer for one and half hours at ambient temperature under nitrogen atmosphere. The resultant solution obtained can be further processed as desired.
Example 2
To a dry 50 ml_ round bottom flask equipped with magnetic stirrer, 3.8859 g (0.01206 mol) of 3, 3', 4, 4 -benzophenone tetracarboxylic dianhydride (BTDA) was added. Then 3.6995 g (0.06156 mol) of isopropyl alcohol and 0.750 g mixture of N- methyl-2-pyrrolidone and N, N' dimethyl acetamide were added to the flask. The reaction mixture was refluxed for 2 hours with stirring under the nitrogen atmosphere. After 2 hours, the solution was cooled to ambient temperature. After cooling the solution 1 .3008 g (0.01203 mol) of m-phenylene diamine and 0.3637 g (0.00182 mol) of 4, 4 -oxydianiline were added and reaction mixture was thoroughly mixed on magnetic stirrer for one and half hours at ambient temperature under nitrogen atmosphere. The resultant solution obtained can be further processed as desired.
Example 3
To a dry 50 ml_ round bottom flask equipped with magnetic stirrer, 3.1773 g (0.00986 mol) of 3, 3", 4, 4'-benzophenone tetracarboxylic dianhydride (BTDA) was added. Then 4.4617 g (0.06019 mol) of n-buty alcohol and 1 g mixture of N-methyl- 2-pyrrolidone and N, N' dimethyl acetamide were added to the flask. The reaction mixture was refluxed for 2 hours with stirring under the nitrogen atmosphere. After 2 hours, the solution was cooled to ambient temperature. After cooling the solution 1 .0636 g (0.00984 mol) of m-phenylene diamine and 0.29974 g (0.00148 mol) of 4, 4'-oxydianiline were added and reaction mixture was thoroughly mixed on magnetic stirrer for one and half hours at ambient temperature under nitrogen atmosphere. The resultant solution obtained can be further processed as desired. Example 4
To a dry 50 ml_ round bottom flask equipped with magnetic stirrer, 3.7068 g (0.01 50 mol) of 3, 3', 4, 4'-benzophenone tetracarboxylic dianhydride (BTDA) was added. Then 3.9554 g (0.0533 mol) of n-butyl alcohol and g mixture of N-methyl-2- pyrrolidone and N, N'-dimethyl acetamide were added to the flask. The reaction mixture was refluxed for 2 hours with stirring under the nitrogen atmosphere. After 2 hours, the solution was cooled to ambient temperature. After cooling the solution 1 .2409 g (0.01 147 mol) of m-phenylene diamine and 0.3469 g (0.00173 mol) of 4, 4'- oxydianiline were added and reaction mixture was thoroughly mixed on magnetic stirrer for one and half hours at ambient temperature under nitrogen atmosphere. The resultant solution obtained can be further processed as desired. Example 5
To a dry 50 mL round bottom flask equipped with magnetic stirrer, 3.1773 g (0.00986 mol) of 3, 3', 4, 4'-benzophenone tetracarboxylic dianhydride (BTDA) was added. Then 4.4617 g (0.06019 mol) of iso butyl alcohol and 1 g mixture of N- methyl-2-pyrrolidone and N, N'-dimethyl acetamide were added to the flask. The reaction mixture was refluxed for 2 hours with stirring under the nitrogen atmosphere. After 2 hours, the solution was cooled to ambient temperature. After cooling the solution 1 .0636 g (0.00984 mol) of m-phenylenediamine and 0.29974 g (0.00148 mol) of 4, 4'-oxydianiline were added and reaction mixture was thoroughly mixed on magnetic stirrer for one and half hours at ambient temperature under nitrogen atmosphere. The resultant solution obtained can be further processed as desired. Example 6
To a dry 50 mL round bottom flask equipped with magnetic stirrer, 3.7068 g (0.01 150 mol) of 3, 3', 4, 4'-benzophenone tetracarboxylic dianhydride (BTDA) was added. Then 3.9554 g (0.0533 mol) of tert-butyl alcohol and g mixture of N-methyl-2- pyrrolidone and N, N'-dimethyl acetamide were added to the flask. The reaction mixture was refluxed for 2 hours with stirring under the nitrogen atmosphere. After 2 hours, the solution was cooled to ambient temperature. After cooling the solution 1.2409 g (0.01 147 mol) of m-phenylenediamine and 0.3469 g (0.00173 mol) of 4, 4 - oxydianiline were added and reaction mixture was thoroughly mixed on magnetic stirrer for one and half hours at ambient temperature under nitrogen atmosphere. The resultant solution obtained can be further processed as desired.
Example 7
To a dry 50 mL round bottom flask equipped with magnetic stirrer, 3.1773 g (0.00986 mol) of 3, 3', 4, 4'-benzophenone tetracarboxylic dianhydride (BTDA) was added. Then 4.4617 g (0.06019 mol) of iso butyl alcohol and 1 g mixture of N- methyl-2-pyrrolidone and N, N'-dimethyl acetamide were added to the flask. The reaction mixture was refluxed for 2 hours with stirring under the nitrogen atmosphere. After 2 hours, the solution was cooled to ambient temperature. After cooling the solution 1 .0636 g (0.00984 mol) of m-phenylene diamine and 0.29974 g (0.00148 mol) of 4, 4'-oxydianiline were added and reaction mixture was thoroughly mixed on magnetic stirrer for one and half hours at ambient temperature under nitrogen atmosphere. The resultant solution obtained can be further processed as desired. Example 8
To a dry 50 mL round bottom flask equipped with magnetic stirrer, 3.7068 g (0.01 150 mol) of 3, 3', 4, 4 -benzophenone tetracarboxylic dianhydride (BTDA) was added. Then 3.9554 g (0.0533 mol) of tert-butyl alcohol and g mixture of N-methyl-2- pyrrolidone and N, ' dimethyl acetamide were added to the flask. The reaction mixture was refluxed for 2 hours with stirring under the nitrogen atmosphere. After 2 hours, the solution was cooled to ambient temperature. After cooling the solution 1.2409 g (0.01 147 mol) of m-phenylene diamine and 0.3469 g (0.00173 mol) of 4, 4'- oxydianiline were added and reaction mixture was thoroughly mixed on magnetic stirrer for one and half hours at ambient temperature under nitrogen atmosphere. The resultant solution obtained can be further processed as desired.
Example 9
To a dry 50 mL round bottom flask equipped with magnetic stirrer, 3.1773 g (0.00986 mol) of 3, 3', 4, 4'-benzophenone tetracarboxylic dianhydride (BTDA) was added. Then 4.4617 g (0.06019 mol) of tert-butyl alcohol and 1 g mixture of N- methyl-2-pyrrolidone and N, N'-dimethyl acetamide were added to the flask. The reaction mixture was refluxed for 2 hours with stirring under the nitrogen atmosphere. After 2 hours, the solution was cooled to ambient temperature. After cooling the solution 1.0636 g (0.00984 mol) of m-phenylene diamine and 0.29974 g (0.00148 mol) of 4, 4'-oxydianiline were added and reaction mixture was thoroughly mixed on magnetic stirrer for one and half hours at ambient temperature under nitrogen atmosphere. The resultant solution obtained can be further processed as desired. Example 10
To a dry 50 mL round bottom flask equipped with magnetic stirrer, 2.9268 g (0.00908 mol) of 3, 3', 4, 4'-benzophenone tetracarboxylic dianhydride (BTDA) was added. Then 4.8195 g (0.04812 mol) of cyclohexanol and 1 g mixture of N-methyl-2- pyrrolidone and N, N' dimethyl acetamide were added to the flask. The reaction mixture was refluxed for 2 hours with stirring under the nitrogen atmosphere. After 2 hours, the solution was cooled to ambient temperature. After cooling the solution 0.9798 g (0.00906 mol) of m-phenylene diamine and 0.2739 g (0.00137 mol) of 4,4'- oxydianiline were added and reaction mixture was thoroughly mixed on magnetic stirrer for one and half hours at ambient temperature under nitrogen atmosphere. The resultant solution obtained can be further processed as desired.
Example 11
To a dry 50 mL round bottom flask equipped with magnetic stirrer, 3.9024 g (0.0121 1 mol) of 3, 3', 4, 4'-benzophenone tetracarboxylic dianhydride (BTDA) was added. Then 3.9259 g (0.03920 mol) of cyclohexanol and 1 g mixture of N-methyl-2- pyrrolidone and N, N' dimethyl acetamide were added to the flask. The reaction mixture was refluxed for 2 hours with stirring under the nitrogen atmosphere. After 2 hours, the solution was cooled to ambient temperature. After cooling the solution 1 .3064 g (0.01208 mol) of m-phenylene diamine and 0.3653 g (0.00182 mol) of 4, 4 - oxydianiline were added and reaction mixture was thoroughly mixed on magnetic stirrer for one and half hours at ambient temperature under nitrogen atmosphere. The resultant solution obtained can be further processed as desired.

Claims

1. A process for the preparation of amino functionalized oligoimide Telechelics comprising the steps of:
i Reacting dianhydride and higher alcohol to obtain diacid-diester;
ii Contacting in an inert atmosphere the product obtained in step (i) with polar aprotic solvents at a temperature in the range of 25 °C to 80 °C for a period of 2 to 64 hours with agitation;
iii Adding Diamine to the solution obtained in step (ii) followed by stirring the reaction mixture vigorously for a period in the range of 2 to 6 hours at room temperature (25 °C) to obtain Polyamic ester;
iv Curing the compound of step (iii) to obtain compound of formula I.
2. The process for the preparation of amino functionalized oligoimide Telechelics as claimed in claim 1 , wherein the higher alcohol is selected from the group consisting isopropyl alcohol, n-butyl alcohol, t-butyl alcohol, cyclohexanol.
3. The process for the preparation of amino functionalized oligoimide Telechelics as claimed in claim 1 , wherein the inert gas used in step (ii) is selected from the group consisting nitrogen or argon.
4. The process for the preparation of amino functionalized oligoimide Telechelics as claimed in claim 1 , wherein the dianhydride is selected from 1 ,2,4,5-benzene tetracarboxylic acid dianhydride, 2,3,4,5-thiophene tetracarboxylic acid dianhydride, 2,3,5,6-pyrazine tetracarboxylic aid dianhydride, 2,3,3',4'-benzophenone tetracarboxylic dianhydride, 2, 2', 3,3'- benzophenone tetracarboxylic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, pyromellitic dianhydride, 2, 3, 3', 4'- biphenyl tetracarboxylic dianhydride, 3,3',4,4'-biphenyl tetracarboxylic dianhydride, 2,3,3',4'-benzophenone tetracarboxylic dianhydride, 2, 2', 3, 3'- benzophenone tetracarboxylic dianhydride, 1 ,4,5,8-naphthalenetetracarboxylic dianhydride, perylene-3,4,9,10-tetracarboxylic dianhydride, 4,4'-oxydiphthalic anhydride, 3,3'-oxydiphthalic anhydride, 4,4'-(hexafluoro isopropylidine) diphthalic anhydride, 4,4'-isopropylidene diphthalic anhydride, 3,4'-isopropylidene diphthalic anhydride, 3,3'-isopropylidene diphthalic anhydride, 4,4'-sulphonyl diphthalic anhydride, 4,4'methylene diphthalic anhydride, 4,4'thiodiphthalic anhydride, 4,4'-ethylidene diphthalic anhydride, phenyl trifluoroethylidene diphthalic anhydride, 2,3,6,7-naphthalene tetracarboxylic dianhydride, 1 ,2,5,6- naphthalene tetracarboxylic dianhydride.
5. The process for the preparation of amino functionalized oligoimide Telechelics as claimed in claim 1 , wherein the diamine is selected from m- phenylene diamine, p-phenylene diamine, 3,3'-oxydianiline, 4,4'-oxydianiline, 3,4 -oxydianiline, 4,4'-diaminodiphenyl methane, 3.4'-diaminodiphenyl methane, 4,4'diaminb diphenyl propane, 4,4'-diamino benzophenone, 3,3'- diamino benzophenone, m-xylenediamine, p-xylenediamine, 4,4'- diaminodiphenyl sulfone, benzidine, 3,3 -dimethoxy benzidine dihydrochloride, 2,2'-dimethyl benzidine, 3,3'-dimethyl benzidine, 4,4'-diaminobiphenyl, 4,4'- diaminobenzophenone, 4,4'-diamino benzanilide either alone or their combinations.
6. The process for the preparation of amino functionalized oligoimide Telechelics as claimed in claim 1 , wherein the polar aprotic solvents is selected from dimethyl sulphoxide, dimethyl formamide, dioxane, N-methyl-2- pyrrolidone, Ν,Ν' - dimethyl acetamide, N-cyclohexyl-2-pyrrolidone, ionic liquids.
7. The process for the preparation of amino functionalized oligoimide Telechelics as claimed in claim 1 , wherein the compound obtained in step 3 is cured with compounds selected from diepoxy, dicarboxyl, anhydride, diisocyanates.
8. The amino functionalized oligoimide Telechelics obtained by the process as claimed in claim 1 , have an improved shelf-life of 3 months when stored at room temperature.
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