Title of Invention	AN IMPROVED PROCESS FOR THE PREPARATION OF A POLYIMIDE.
Abstract	An improved process for the preparation of polyimide by reacting with a dianhydride in an inert atmosphere optionally in the presence of an organic solvent, at a temperature in the range of 150 to 300°C, for a period ranging between 2 to 20 hours, cooling the reaction mixture to a temperature ranging from 25°C to 35°C, precipitating the product by adding the reaction mixture to methanol and separating the polyimide by conventional methods.

Title of Invention

AN IMPROVED PROCESS FOR THE PREPARATION OF A POLYIMIDE.

Abstract

An improved process for the preparation of polyimide by reacting with a dianhydride in an inert atmosphere optionally in the presence of an organic solvent, at a temperature in the range of 150 to 300°C, for a period ranging between 2 to 20 hours, cooling the reaction mixture to a temperature ranging from 25°C to 35°C, precipitating the product by adding the reaction mixture to methanol and separating the polyimide by conventional methods.

Full Text	The present invention relates to an improved process for the preparation of a polyimide. More particularly it relates to the said novel polyimides having formula (1). These novel polyimides are prepared by reacting new aromatic diamine of formula (2) with different dianhydrides of formula (3). (Formula Removed) wherein Ar is selected from the group consisting of (Formula Removed) The novel aromatic: diamine of formula (2) is prepared by the process, fully described and claimed in our co-pending patent, application No.l098/Del/2001. Aromatic polyimides are well known for their excellent high temperature resistance, good mechanical strength and superior electrical properties. Therefore these polymers have major impact on moldings and adhesive, particularly in aerospace composites, coatings, electrical applications. However they are difficult to process in fully cyclized (imidized) form due to their high melting or softening temperature and low solubility in most organic solvents. Current and prior attempts to solubilize and process aromatic polyimides have been made through synthetic modification of the basic rigid chain structure by introduction flexibilising linkages, molecular asymmetry or addition of bulky side group into the backbone. Incorporation of an arylene ether linkage into a polymer macrochain is known to improve solubility and impart processability to the polymer with little reduction in thermal stability. Hence combination of aryl ether and long alkyl side group should increase solubility of polymers without extreme losss of thermal stability. diamine of the formula (2) is a good monomer for the synthesis of such polyimides. These polyimides containing alkyl side group have utility as coating material having pretilt angle for liquid crystal display devices and it is likely to have good dielectric properties. The novel polyimides film containing ether and pendant alkyl side prepared from a novel diamine (2), by using a two step process are claimed and described in our co-pending application no. 1097/Del/2001. The objective of the present invention is to provide novel polyimides with enhanced solubility. Another objective is to provide an improved single step process for the preparation of these polyimides. Accordingly, the present invention provides an improved process for the preparation of polyimide of formula 1 (Formula Removed) which comprises reacting compound (2) with a dianhydride compound (3) (Formula Removed) wherein Ar is selected from the group consisting of wherein Ar is selected from the group consisting of (Formula Removed) in an inert atmosphere optionally in the presence of an organic solvent, at a temperature in the range of 150 to 300°C, for a period ranging between 2 to 20 hours, cooling the reaction mixture to a temperature ranging from 25°C to 35°C, precipitating the product by adding the reaction mixture to methanol and separating the polyimide by conventional methods. In an embodiment of the present invention the dianhydride used is selected from the group consisting of pyromellitic dianhydride (PMDA), 3,3' 4,4'-biphenyltetracarboxylic dianhydride (BPDA), 4,4'-oxydipthalic anhydride (ODPA), 3,3*4,4'- benzophenoneltetracarboxylic dianhydride (BTDA), 1,1-dimethyl silane, dianhydride (SiDA), 4,4'-hexafluroisopropylidenediphthalic anhydride (6FDA) and 3,3',4,4'- sulfonyltetracarboxylic dianhydride (SDA). In yet another embodiment the organic solvent used is selected from the group consisting of nitrobenzene, chlorophenol, m-cresol and phenol, preferably m-cresol. In still another embodiment the non-solvent used for the precipitation of the product is miscible in the solvent used in the reaction and non-solvent to the product such as methanol. The details of the constituents required and process for the preparation of polyimides provided by the present invention is described herein below with examples, which are illustrative only and should not be construed to limit the scope of the present invention in any manner. Example 1 A 25 ml three necked round bottom flask equipped with an overhead stirrer, a nitrogen gas inlet and a guard tube was charged with 3,3',4,4'-biphenyltetracarboxylic dianhydride BPDA) [0.50 g, ,1.70 mmol] and diamine (2) [0.70 g, 1.70 mmol] in m-cresol [8 mL, 15% solid content]. The reaction mixture was heated under the stream of dry nitrogen gas for 7 h in an oil bath maintained at 200 °C. After cooling the viscous solution was poured slowly in methanol to precipitate polymer. Polymer was washed with methanol and stirred overnight in methanol to remove w-cresol. Polymer after filtration was dried in a vacuum oven at 60 °C for 12 h. Yield of the polymer obtained was 98.30%. Example - 2: A 25 mL three necked round bottom flask equipped with a magnetic stirring bar, a nitrogen gas inlet and a guard tube was charged with pyromellitic dianhydride (PMDA) [0.50 g, 2.3 mmol] and N,N-dimethylacetamide [8 mL, 15% solid content]. The reaction mixture was then cooled to 5 °C and diamine (2) [0.94 g, 2.3 mmol] was added in small portions, with constant stirring. The reaction mixture was then allowed to come to room temperature slowly and left at that temperature for another 24 h. The viscous polyamic acid solution obtained was then cast on a glass plate and heated in an oven under nitrogen atmosphere, initially at 100 °C for 1 h, then 200 °C for 2 h and 300 °C for 3 h, with gradual increase in temperature. A tough and transparent polyimide film was obtained. Yield of the obtained polymer was 98.02%. Example - 3 A 25 mL three necked round bottom flask equipped with an overhead stirrer, a nitrogen gas inlet and a guard tube was charged with 4,4'-oxydiphthalic anhydride (ODPA) [0.50 g, 1.61 mmol] and diamine (2) [0.66 g, 1.61 mmol] in m-cresol [8 mL, 15% solid content]. The reaction mixture was heated under the stream of dry nitrogen gas for 8 h in an oil bath maintained at 200 °C. After cooling, the viscous solution was poured slowly in methanol to precipitate polymer. Polymer was washed with methanol and stirred overnight in methanol to remove m-cresol. Polymer after filtration was dried in a vacuum oven at 60 °C for 12 h. Yield of the polymer obtained was 98.8%. Example - 4 A 25 mL three necked round bottom flask equipped with a magnetic stirring bar, a nitrogen gas inlet and a guard tube was charged with 3,3', 4,4'-benzophenonetetracarboxylic dianhydride (BTDA) [0.50 g, 1.55 mmol] and N-methylpyrolidone [8 mL, 15% solid content]. The reaction mixture was then cooled to 5 °C and diamine (2) [0.64 g, 1.55 mmol] was added in small portions, with constant stirring. Reaction mixture was then allowed to come to room temperature slowly and left at that temperature for another 24 h. The viscous polyamic acid solution obtained was then cast on a glass plate and heated in an oven under nitrogen atmosphere, initially at 100 °C for 1 h, then 200 °C for 2 h and 300 °C for 3 h, with gradual increase in temperature. A tough and transparent polyimide film was obtained. Yield of the obtained polymer was 98.22%. Example - 5 A 25 mL three necked round bottom flask equipped with an overhead stirrer, a nitrogen gas inlet and a guard tube was charged with 4,4'-hexafluroisopropylidenediphthalic anhydride (6FDA) [0.50 g, 1.19 mmol] and diamine (2) [0.49 g, 1.19 rnmol] in m-cresol [8 mL, 15% solid content]. The reaction was heated under the stream of dry nitrogen gas for 8 h in an oil bath maintained at 200 °C. After cooling the viscous solution was poured slowly in methanol to precipitate polymer. Polymer was washed with methanol and stirred overnight in methanol to remove m-cresol. Polymer after filtration was dried in a vacuum oven at 60 °C for 12 h. Yield of the polymer obtained was 98.30%. Example - 6 A 25 mL three necked round bottom flask equipped with an overhead stirrer, a nitrogen gas inlet and a guard tube was charged with bis (3,4-dicarboxyphenyl)-dimethylsilane dianhydride (SiDA) [0.50 g, 1.42 mmol] and diamine (2) [0.58 g, 1.42 mmol] in m-cresol [8 mL, 15% solid content]. The reaction was heated under the stream of dry nitrogen gas for 8 h. in an oil bath maintained at 200 °C. After cooling the viscous solution was poured slowly in methanol to precipitate polymer. Polymer was washed with methanol and stirred overnight in methanol to remove m-cresol. Polymer after filtration was dried in a vacuum oven at 60 °C for 12 h Yield of the polymer obtained was 98.53%. This invention provides an easy and high yielding procedure for the synthesis of novel polyimides (1), prepared by reacting a novel diamine (2) with different dianhydride of formula (3). The novel polyimides prepared are soluble in most of the organic solvents, like chloroform, N-methylpyrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, m-cresol, toluene, xylene, pryidine and nitrobenzene. These polymers can be processed at low temperature due to their low glass transition temperature (Tg). Also such polyimides containing long alkyl side chain have utility as coating material having pretilt angle for liquid crystal display devices. We claim: 1. An improved process for the preparation of polyimide of formula 1 (Formula Removed) which comprises reacting compound (2) with a dianhydride compound (3) (Formula Removed) wherein Ar is selected from the group consisting of (Formula Removed) in an inert atmosphere optionally in the presence of an organic solvent, at a temperature in the range of 150 to 300°C, for a period ranging between 2 to 20 hours, cooling the reaction mixture to a temperature ranging from 25°C to 35°C, precipitating the product by adding the reaction mixture to methanol and separating the polyimide by conventional methods. 2. An improved process as claimed in claim 1, wherein the dianhydride used is selected from the group consisting of pyromellitic dianhydride (PMDA), 3,3', 4,4'-biphenyltetracarboxylic dianhydride (BPDA), 4,4'-oxydipthalic anhydride (ODPA), 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA),1,1- dimethyl silane dianhydride (SiDA), 4,4'-hexafluroisopropylidenediphthalic anhydride (6FDA) and 3,3',4,4'-sulfonyltetracarboxylic dianhydride (SDA). 3. An improved process as claimed in claims 1-2, wherein the organic solvent used is selected from the group consisting of nitrobenzene, chlorophenol, m-cresol and phenol, preferably m-cresol. 4. An improved process for the preparation of polyimide substantially as herein described, with reference to the examples.

Full Text

The present invention relates to an improved process for the preparation of a polyimide. More particularly it relates to the said novel polyimides having formula (1). These novel polyimides are prepared by reacting new aromatic diamine of formula (2) with different dianhydrides of formula (3).

(Formula Removed)

wherein Ar is selected from the group consisting of
(Formula Removed)
The novel aromatic: diamine of formula (2) is prepared by the process, fully described and claimed in our co-pending patent, application No.l098/Del/2001.
Aromatic polyimides are well known for their excellent high temperature resistance, good mechanical strength and superior electrical properties. Therefore these polymers have major impact on moldings and adhesive, particularly in aerospace composites, coatings, electrical applications. However they are difficult to process in fully cyclized (imidized) form due to their high melting or softening temperature and low solubility in most organic solvents. Current and prior attempts to solubilize and process aromatic polyimides have been made through synthetic modification of the basic rigid chain structure by introduction flexibilising linkages, molecular asymmetry or addition of bulky side group into the backbone. Incorporation of an arylene ether linkage into a polymer macrochain is known to improve solubility and impart processability to the polymer with little reduction in thermal stability. Hence combination of aryl ether and long alkyl side group should increase solubility of polymers without extreme losss of thermal stability.

diamine of the formula (2) is a good monomer for the synthesis of such polyimides. These
polyimides containing alkyl side group have utility as coating material having pretilt angle
for liquid crystal display devices and it is likely to have good dielectric properties.
The novel polyimides film containing ether and pendant alkyl side prepared from a novel
diamine (2), by using a two step process are claimed and described in our co-pending
application no. 1097/Del/2001.
The objective of the present invention is to provide novel polyimides with enhanced
solubility.
Another objective is to provide an improved single step process for the preparation of these
polyimides.
Accordingly, the present invention provides an improved process for the preparation of
polyimide of formula 1

(Formula Removed)

which comprises reacting compound (2) with a dianhydride compound (3)

(Formula Removed)
wherein Ar is selected from the group consisting of

wherein Ar is selected from the group consisting of (Formula Removed)

in an inert atmosphere optionally in the presence of an organic solvent, at a temperature in
the range of 150 to 300°C, for a period ranging between 2 to 20 hours, cooling the reaction
mixture to a temperature ranging from 25°C to 35°C, precipitating the product by adding the
reaction mixture to methanol and separating the polyimide by conventional methods.
In an embodiment of the present invention the dianhydride used is selected from the group
consisting of pyromellitic dianhydride (PMDA), 3,3' 4,4'-biphenyltetracarboxylic
dianhydride (BPDA), 4,4'-oxydipthalic anhydride (ODPA), 3,3*4,4'-
benzophenoneltetracarboxylic dianhydride (BTDA), 1,1-dimethyl silane, dianhydride
(SiDA), 4,4'-hexafluroisopropylidenediphthalic anhydride (6FDA) and 3,3',4,4'-
sulfonyltetracarboxylic dianhydride (SDA).
In yet another embodiment the organic solvent used is selected from the group consisting of
nitrobenzene, chlorophenol, m-cresol and phenol, preferably m-cresol.
In still another embodiment the non-solvent used for the precipitation of the product is
miscible in the solvent used in the reaction and non-solvent to the product such as methanol.
The details of the constituents required and process for the preparation of polyimides
provided by the present invention is described herein below with examples, which are
illustrative only and should not be construed to limit the scope of the present invention in
any manner.
Example 1
A 25 ml three necked round bottom flask equipped with an
overhead stirrer, a nitrogen gas inlet and a guard tube
was charged with 3,3',4,4'-biphenyltetracarboxylic dianhydride BPDA) [0.50 g,

,1.70 mmol] and diamine (2) [0.70 g, 1.70 mmol] in m-cresol [8 mL, 15% solid content]. The reaction mixture was heated under the stream of dry nitrogen gas for 7 h in an oil bath maintained at 200 °C. After cooling the viscous solution was poured slowly in methanol to precipitate polymer. Polymer was washed with methanol and stirred overnight in methanol to remove w-cresol. Polymer after filtration was dried in a vacuum oven at 60 °C for 12 h. Yield of the polymer obtained was 98.30%.
Example - 2:
A 25 mL three necked round bottom flask equipped with a magnetic stirring bar, a nitrogen gas inlet and a guard tube was charged with pyromellitic dianhydride (PMDA) [0.50 g, 2.3 mmol] and N,N-dimethylacetamide [8 mL, 15% solid content]. The reaction mixture was then cooled to 5 °C and diamine (2) [0.94 g, 2.3 mmol] was added in small portions, with constant stirring. The reaction mixture was then allowed to come to room temperature slowly and left at that temperature for another 24 h. The viscous polyamic acid solution obtained was then cast on a glass plate and heated in an oven under nitrogen atmosphere, initially at 100 °C for 1 h, then 200 °C for 2 h and 300 °C for 3 h, with gradual increase in temperature. A tough and transparent polyimide film was obtained. Yield of the obtained polymer was 98.02%.
Example - 3
A 25 mL three necked round bottom flask equipped with an overhead stirrer, a nitrogen gas inlet and a guard tube was charged with 4,4'-oxydiphthalic anhydride (ODPA) [0.50 g, 1.61 mmol] and diamine (2) [0.66 g, 1.61 mmol] in m-cresol [8 mL, 15% solid content]. The reaction mixture was heated under the stream of dry nitrogen gas for 8 h in an oil bath maintained at 200 °C. After cooling, the viscous solution was poured slowly in methanol to precipitate polymer. Polymer was washed with methanol and stirred overnight in methanol to remove m-cresol. Polymer after filtration was dried in a vacuum oven at 60 °C for 12 h. Yield of the polymer obtained was 98.8%.

Example - 4
A 25 mL three necked round bottom flask equipped with a magnetic stirring bar, a nitrogen gas inlet and a guard tube was charged with 3,3', 4,4'-benzophenonetetracarboxylic dianhydride (BTDA) [0.50 g, 1.55 mmol] and N-methylpyrolidone [8 mL, 15% solid content]. The reaction mixture was then cooled to 5 °C and diamine (2) [0.64 g, 1.55 mmol] was added in small portions, with constant stirring. Reaction mixture was then allowed to come to room temperature slowly and left at that temperature for another 24 h. The viscous polyamic acid solution obtained was then cast on a glass plate and heated in an oven under nitrogen atmosphere, initially at 100 °C for 1 h, then 200 °C for 2 h and 300 °C for 3 h, with gradual increase in temperature. A tough and transparent polyimide film was obtained. Yield of the obtained polymer was 98.22%.
Example - 5
A 25 mL three necked round bottom flask equipped with an overhead stirrer, a nitrogen gas inlet and a guard tube was charged with 4,4'-hexafluroisopropylidenediphthalic anhydride (6FDA) [0.50 g, 1.19 mmol] and diamine (2) [0.49 g, 1.19 rnmol] in m-cresol [8 mL, 15% solid content]. The reaction was heated under the stream of dry nitrogen gas for 8 h in an oil bath maintained at 200 °C. After cooling the viscous solution was poured slowly in methanol to precipitate polymer. Polymer was washed with methanol and stirred overnight in methanol to remove m-cresol. Polymer after filtration was dried in a vacuum oven at 60 °C for 12 h. Yield of the polymer obtained was 98.30%.
Example - 6
A 25 mL three necked round bottom flask equipped with an overhead stirrer, a nitrogen gas inlet and a guard tube was charged with bis (3,4-dicarboxyphenyl)-dimethylsilane dianhydride (SiDA) [0.50 g, 1.42 mmol] and diamine (2) [0.58 g, 1.42 mmol] in m-cresol [8 mL, 15% solid content]. The reaction was heated under the stream of dry nitrogen gas for 8 h. in an oil bath maintained at

200 °C. After cooling the viscous solution was poured slowly in methanol to precipitate polymer. Polymer was washed with methanol and stirred overnight in methanol to remove m-cresol. Polymer after filtration was dried in a vacuum oven at 60 °C for 12 h Yield of the polymer obtained was 98.53%.
This invention provides an easy and high yielding procedure for the synthesis of novel polyimides (1), prepared by reacting a novel diamine (2) with different dianhydride of formula (3). The novel polyimides prepared are soluble in most of the organic solvents, like chloroform, N-methylpyrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, m-cresol, toluene, xylene, pryidine and nitrobenzene. These polymers can be processed at low temperature due to their low glass transition temperature (Tg). Also such polyimides containing long alkyl side chain have utility as coating material having pretilt angle for liquid crystal display devices.

We claim:
1. An improved process for the preparation of polyimide of formula 1

(Formula Removed)
which comprises reacting compound (2) with a dianhydride compound (3)

(Formula Removed)
wherein Ar is selected from the group consisting of
(Formula Removed)
in an inert atmosphere optionally in the presence of an organic solvent, at a temperature in the range of 150 to 300°C, for a period ranging between 2 to 20 hours, cooling the reaction mixture to a temperature ranging from 25°C to 35°C, precipitating the product by adding the reaction mixture to methanol and separating the polyimide by conventional methods.

2. An improved process as claimed in claim 1, wherein the dianhydride used is
selected from the group consisting of pyromellitic dianhydride (PMDA), 3,3',
4,4'-biphenyltetracarboxylic dianhydride (BPDA), 4,4'-oxydipthalic anhydride
(ODPA), 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA),1,1-
dimethyl silane dianhydride (SiDA), 4,4'-hexafluroisopropylidenediphthalic
anhydride (6FDA) and 3,3',4,4'-sulfonyltetracarboxylic dianhydride (SDA).
3. An improved process as claimed in claims 1-2, wherein the organic solvent used
is selected from the group consisting of nitrobenzene, chlorophenol, m-cresol and
phenol, preferably m-cresol.
4. An improved process for the preparation of polyimide substantially as herein
described, with reference to the examples.

Documents:

1094-del-2001-abstract.pdf

1094-del-2001-claims.pdf

1094-del-2001-correspondence-others.pdf

1094-del-2001-correspondence-po.pdf

1094-del-2001-description (complete).pdf

1094-del-2001-form-1.pdf

1094-del-2001-form-18.pdf

1094-del-2001-form-2.pdf

1094-del-2001-form-3.pdf

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Patent Number

242164

Indian Patent Application Number

1094/DEL/2001

PG Journal Number

34/2010

Publication Date

20-Aug-2010

Grant Date

17-Aug-2010

Date of Filing

31-Oct-2001

Name of Patentee

COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH

Applicant Address

RAFI MARG, NEW DELHI-110001, INDIA.

Inventors:

#	Inventor's Name	Inventor's Address
1	SANTOSH BABURAO MHASKE	NATIONAL CHEMICAL LABORATORY, PUNE-411008, MAHARASHTRA, INDIA.
2	SUBASH PUNDLIK VERNEKAR	REGES MERCIER FROM LABORATOIRE DES MATERIAUX ORGANIQUES A PROPRIETES SPECIQUES-UPR 9031, VERNAISON, LYON, FRANCE.

PCT International Classification Number

C08G 69/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA