Title of Invention	"A PROCESS FOR THE PREPARATION OF A NOVEL THERMOSETTING POLYMER USEFUL FOR ENGINEERING APPLICATIONS"
Abstract	In the present invention, a process for the preparation of a novel thermosetting polymer useful for engineering applications, specifically Epoxy novolac - Bismaleimide, has been given. The resulting novel thermosetting polymer has high glass transition temperature , good thermal stability, reduced moisture uptake and a good processing window thus providing a useful and novel cost effective engineering material.

Title of Invention

"A PROCESS FOR THE PREPARATION OF A NOVEL THERMOSETTING POLYMER USEFUL FOR ENGINEERING APPLICATIONS"

Abstract

In the present invention, a process for the preparation of a novel thermosetting polymer useful for engineering applications, specifically Epoxy novolac - Bismaleimide, has been given. The resulting novel thermosetting polymer has high glass transition temperature , good thermal stability, reduced moisture uptake and a good processing window thus providing a useful and novel cost effective engineering material.

Full Text	The present invention relates to a process for the preparation of a novel thermosetting polymer useful for engineering applications. The present invention particularly relates to Epoxy novolac - Bismaleimide polymer useful for engineering applications. The main usage of the novel polymer of the present invention is the preparation of a tailor-made new material for use in high performance applications such as Electronics and Aerospace industries. The novel polymer material produced by the process of the present invention has a high glass transition temperature 'Tg' and a high thermal stability to suit engineering applications wherein a high thermal stability is required. Among several thermosetting polymers, epoxy resins are the largest segment of cured thermosetting polymers which are used to make structural composites in the aerospace^ and electronic industries because of their good thermal and electrical properties. The applications of epoxies are extensive because of their ease to process. However, their upper operating temperature limits their use for structural applications. The existing epoxy systems suffer mainly from brittleness and high levels of moisture uptake. With respect to brittleness, extensive studies were made for toughening [ACS Polym. Prepr. 26 (1985) 277], [Polym. Engg. Sc.l3,(l973)29] . Conventional rubbers [J. Polym. Sci., Polym. Chem.23 (1985)1163] and reactive elastomer such as (Carboxyl terminated butadiene nitrile) CTBN and (Amino terminated butadiene nitrile) ATBN [J. Appl. Polym. Sci. 28 (1983) 2567], [ Polym.Ad. Technol. (1990), 211] were reported to improve the toughness. The toughness could be improved by dispersing small rigid domains into the epoxy matrix (Rubber modified thermoset resins ACS, Washington 1984). However, the reduction of glass transition temperature and mechanical properties were the drawbacks. To overcome the deteriorationjn properties due to moisture uptake, recently, a new approach has been practiced which consists of the formulation of thermoset / thermoset blending to balance the advantages and disadvantages of the resin systems. For eg.,Tetra Glycidyl Ether of Diamino Diphenyl Methane (TGDDM)/ Diamino Diphenyl Sulphone (DOS) system mixed with a bismaleimide (BMI) monomer. TGDDM/DDS system mainly suffers from brittleness and moisture uptake where as BMI has excellent thermal and thermal oxidative stability and least tendency to absorb moisture [J. Applied Polym. Sci., Vol 69 (1998) 1029 - 1042, J. Polym. Engg. & Sci., Vol 35, No 17 (1995) 1353 -1358]. These systems, owing to their peculiar molecular structures showed improvement in properties [J. of Material Science22 (1987)3665]. However, these systems are highly viscous which causes difficulty in processing. Through extensive literature survey and patent search using various data bases it was revealed that no report is available to the best of our knowledge on a material which has overcome the earlier drawbacks with a moderate functionality and good processing window. The main object of the present invention is_to provide a process for the preparation of a novel thermosetting polymer useful for engineering applications which obviates the drawbacks as detailed above. Another object of the present invention is to provide a process for the preparation of a novel Epoxy novolac - Bismaleimide polymer having a higher Tg and thermal stability for higher operating temperature. Accordingly, the present invention provides a process for the preparation of a novel thermosetting polymer useful for engineering applications which comprises; dissolving 20-35 weight percentage of one or more aromatic amines in 100 weight percentage of Epoxy novolac under constant stirring at a temperature in the range 70-120°C, adding 2-35% of aromatic amine based Bismaleimide to the resultant solution maintained at a temperature in the range of 70-120°C under constant stirring to obtain a clear melt, subjecting the resultant clear melt so obtained to a multi-step curing at temperatures in the range of 100 - 240°C for a period of at least 4 hrs, to obtain the product. In an embodiment of the present invention the aromatic amine used may preferably to one or more diamines. In another embodiment of the present invention the multi step curing may be effected at a temperature in the range 100 - 130°C for at least 1 hr followed by curing at a temperature in the range of 150 - 200°C for at least 1 hr and final curing at a temperature in the range of200-240°Cforatleastlhr. The detailed steps of the process of the present invention are as follows: 1. Dissolution of 20 - 35 weight percentage of aromatic amine in 100 weight percentage of Epoxy novolac at a temperature in the range of 100 to 130°C. 2. Addition of Bismalemide to the above solution maintained at a temperature in the range of 70 - 120°C to get a clear melt. 3. Subjecting the clear melt obtained by step 2 to multi-step curing. The reaction scheme includes (a) the reaction between Epoxy novolac and amine hardener (b) the reaction between amine hardener and Bismaleimide resulting in an amino terminated Bismaleimide which in turn reacts with Epoxy novolac and (c) a BMI homopolymerisation . All the reactions are parallel and temperature dependent. The reactions (a) and (b) occur at a temperature in the range of 100 - 150°C and the BMI homopolymerisation occurs at a higher temperature in the range of 200-240°C . In order to achieve the complete conversion of the reactants into the product and to ensure better properties from the product, a step wise curing schedule is followed. The novelty lies in providing a process for preparation of thermosetting Epoxy novolac - Bismaleimide polymer useful for engineering applications and curing the polymer in a multi step schedule. Following examples are given by way of illustrations and therefore should not be construed to limit the scope of the present work. EXAMPLE - 1 To 100 parts of Epoxy novolac (EPN), slowly added 32 parts of aromatic diamine hardener at 100°C and constantly stirred to obtain a clear solution. Then added 30% aromatic diamine based Bismaleimide(BMI) under constant stirring. Slowly the temperature was raised to 120°C to get a clear melt. The melt so obtained was cured at 120°C for 1 hr, 150°C for 2hrs followed by a final cure at 220°C for Ihr. The glass transition temperature measured by DSC (Differential Scanning Calorimetry) technique was found to be 191°C. EXAMPLE - 2 28 parts of aromatic amine was dissolved in 100 parts of EPN at 100°C by constant stirring and then added 10%BMI. The stirring was continued to get a clear melt by raising the temperature to 120°C . Then the resultant melt was cured at 120°C for 1 hr, 150°C for 2 hrs followed by a final cure at 220°C for 1 hr. The Tg measured by DSC technique was found to be 213°C. EXAMPLE - 3 28 parts of aromatic amine was dissolved in 100 parts of EPN at 100°C by constant stirring and then added 20%BMI. The stirring was continued to get a clear melt by raising the temperature to 120°C . Then the resultant melt was cured at 120°C for 1 hr, 150°C for 2 hrs followed by a final cure at 220°C for 1 hr. The Tg measured by DSC technique was found to be 191°C. EXAMPLE - 4 28 parts of aromatic amine was dissolved in 100 parts of EPN at 100°C by constant stirring and then added 20%BMI. The stirring was continued to get a clear melt by raising the temperature to 120°C . Then the resultant melt was cured at 120°C for 1 hr, 150°C for 2 hrs followed by a final cure at 220°C for 2 hr. The Tg measured by DSC technique was found to be 228°C. EXAMPLE -5 28 parts of aromatic amine was dissolved in 100 parts of EPN at 100°C by constant stirring and then added 30%BMI. The stirring was continued to get a clear melt by raising the temperature to 120°C . Then the resultant melt was cured at 120°C for 1 hr, 150°C for 2 hrs followed by a final cure at 220°C for 4hr. The Tg measured by DSC technique was found to be 232°C. EXAMPLE - 6 Thermal stability of the cured products were determined using thermogravimetric analysis technique (TGA) which gives information related to the weight loss of the material with respect to temperature (Thermal decomposition). The thermograms showed enhanced thermal stability when compared to unmodified Epoxy systems. It was found that the addition of higher percentage of BMI to the Epoxy novolac-Amine system and curing in a step wise schedule enhanced the glass transition temperature and the thermal stability. It was also found that addition of more than 35% of BMI causes phase separation problems due to the solubility parameters. The novelty of the present invention lies in the preparation of a new material, with a new combination of materials, having better properties such as high Tg and high thermal stability. The drawbacks previously referred to have been obviated. The inventive steps are in choosing a new combination of materials which result in a blend having tailor-made properties such as high glass transition temperature, high thermal stability and good processing window. The main advantages of the process of the present invention are 1. Enhancement of Tg (Glass transition temperature) 2. Increase in thermal stability 3. Reduction in moisture uptake 4. Good processing window (viscosity) 5. Preparation of a new material with tailor made properties to suit the requirements 6. Preparation of a new material within a short time using small amounts of Bismaleimide(BMI) which has resulted in better properties We Claim: 1. A process for the preparation of a novel thermosetting polymer useful for engineering applications which comprises; dissolving 20-35 weight percentage of one or more aromatic amines in 100 weight percentage of Epoxy novolac under constant stirring at a temperature in the range 70-120°C, adding 2-35% of aromatic amine based Bismaleimide to the resultant solution maintained at a temperature in the range of 70-120°C under constant stirring to obtain a clear melt, subjecting the resultant clear melt so obtained to a multi-step curing at temperatures in the range of 100 - 240°C for a period of at least 4 hrs, to obtain the product. 2. The process as claimed in claim 1 where in the aromatic used is preferably a diamine. 3. The process as claimed in claims 1 and 2 where in the multi-step curing is effected at a temperature in the range 100 - 130°C for at least 1 hr, followed by curing at a temperature in the range of 150-200°C for at least 1 hr and final curing at a temperature in the range of 200 - 240°C for at least 1 hr. 4. A process for the preparation of a novel thermosetting polymer useful for engineering applications substantially as herein described with reference to the examples.

Full Text

The present invention relates to a process for the preparation of a novel thermosetting polymer useful for engineering applications. The present invention particularly relates to Epoxy novolac - Bismaleimide polymer useful for engineering applications.
The main usage of the novel polymer of the present invention is the preparation of a tailor-made new material for use in high performance applications such as Electronics and Aerospace industries. The novel polymer material produced by the process of the present invention has a high glass transition temperature 'Tg' and a high thermal stability to suit engineering applications wherein a high thermal stability is required.
Among several thermosetting polymers, epoxy resins are the largest segment of cured thermosetting polymers which are used to make structural composites in the aerospace^ and electronic industries because of their good thermal and electrical properties. The applications of epoxies are extensive because of their ease to process. However, their upper operating temperature limits their use for structural applications.
The existing epoxy systems suffer mainly from brittleness and high levels of moisture uptake. With respect to brittleness, extensive studies were made for toughening [ACS Polym. Prepr. 26 (1985) 277], [Polym. Engg. Sc.l3,(l973)29] . Conventional rubbers [J. Polym. Sci., Polym. Chem.23 (1985)1163] and reactive elastomer such as (Carboxyl terminated butadiene nitrile) CTBN and (Amino terminated butadiene nitrile) ATBN [J. Appl. Polym. Sci. 28 (1983) 2567], [

Polym.Ad. Technol. (1990), 211] were reported to improve the toughness. The toughness could be improved by dispersing small rigid domains into the epoxy matrix (Rubber modified thermoset resins ACS, Washington 1984). However, the reduction of glass transition temperature and mechanical properties were the drawbacks. To overcome the deteriorationjn properties due to moisture uptake, recently, a new approach has been practiced which consists of the formulation of thermoset / thermoset blending to balance the advantages and disadvantages of the resin systems. For eg.,Tetra Glycidyl Ether of Diamino Diphenyl Methane (TGDDM)/ Diamino Diphenyl Sulphone (DOS) system mixed with a bismaleimide (BMI) monomer. TGDDM/DDS system mainly suffers from brittleness and moisture uptake where as BMI has excellent thermal and thermal oxidative stability and least tendency to absorb moisture [J. Applied Polym. Sci., Vol 69 (1998) 1029 - 1042, J. Polym. Engg. & Sci., Vol 35, No 17 (1995) 1353 -1358]. These systems, owing to their peculiar molecular structures showed improvement in properties [J. of Material Science22 (1987)3665]. However, these systems are highly viscous which causes difficulty in processing.
Through extensive literature survey and patent search using various data bases it was revealed that no report is available to the best of our knowledge on a material which has overcome the earlier drawbacks with a moderate functionality and good processing window.
The main object of the present invention is_to provide a process for the preparation of a novel thermosetting polymer useful for engineering applications which obviates the drawbacks as detailed above.

Another object of the present invention is to provide a process for the preparation of a novel Epoxy novolac - Bismaleimide polymer having a higher Tg and thermal stability for higher operating temperature.
Accordingly, the present invention provides a process for the preparation of a novel thermosetting polymer useful for engineering applications which comprises; dissolving 20-35 weight percentage of one or more aromatic amines in 100 weight percentage of Epoxy novolac under constant stirring at a temperature in the range 70-120°C, adding 2-35% of aromatic amine based Bismaleimide to the resultant solution maintained at a temperature in the range of 70-120°C under constant stirring to obtain a clear melt, subjecting the resultant clear melt so obtained to a multi-step curing at temperatures in the range of 100 - 240°C for a period of at least 4 hrs, to obtain the product.
In an embodiment of the present invention the aromatic amine used may preferably to one or more diamines.
In another embodiment of the present invention the multi step curing may be effected at a temperature in the range 100 - 130°C for at least 1 hr followed by curing at a temperature in the range of 150 - 200°C for at least 1 hr and final curing at a temperature in the range of200-240°Cforatleastlhr.
The detailed steps of the process of the present invention are as follows:
1. Dissolution of 20 - 35 weight percentage of aromatic amine in 100 weight
percentage of Epoxy novolac at a temperature in the range of 100 to 130°C.
2. Addition of Bismalemide to the above solution maintained at a temperature in the
range of 70 - 120°C to get a clear melt.
3. Subjecting the clear melt obtained by step 2 to multi-step curing.
The reaction scheme includes (a) the reaction between Epoxy novolac and amine hardener (b) the reaction between amine hardener and Bismaleimide resulting in an amino terminated Bismaleimide which in turn reacts with Epoxy novolac and (c) a BMI homopolymerisation . All the reactions are parallel and temperature dependent. The reactions (a) and (b) occur at a temperature in the range of 100 - 150°C and the BMI homopolymerisation occurs at a higher temperature in the range of 200-240°C . In order to achieve the complete conversion of the reactants into the product and to ensure better properties from the product, a step wise curing schedule is followed.
The novelty lies in providing a process for preparation of thermosetting Epoxy novolac - Bismaleimide polymer useful for engineering applications and curing the polymer in a multi step schedule.
Following examples are given by way of illustrations and therefore should not be construed to limit the scope of the present work.
EXAMPLE - 1
To 100 parts of Epoxy novolac (EPN), slowly added 32 parts of aromatic diamine hardener at 100°C and constantly stirred to obtain a clear solution. Then added 30% aromatic diamine based Bismaleimide(BMI) under constant stirring. Slowly the temperature was raised to 120°C to get a clear melt. The melt so obtained was cured at 120°C for 1 hr, 150°C for 2hrs followed by a final cure at 220°C for Ihr. The glass transition temperature measured by DSC (Differential Scanning Calorimetry) technique was found to be 191°C.
EXAMPLE - 2
28 parts of aromatic amine was dissolved in 100 parts of EPN at 100°C by constant stirring and then added 10%BMI. The stirring was continued to get a clear melt by raising the temperature to 120°C . Then the resultant melt was cured at 120°C for 1 hr, 150°C for 2 hrs followed by a final cure at 220°C for 1 hr. The Tg measured by DSC technique was found to be 213°C.
EXAMPLE - 3
28 parts of aromatic amine was dissolved in 100 parts of EPN at 100°C by constant stirring and then added 20%BMI. The stirring was continued to get a clear melt by raising the temperature to 120°C . Then the resultant melt was cured at 120°C for 1 hr, 150°C for 2 hrs followed by a final cure at 220°C for 1 hr. The Tg measured by DSC technique was found to be 191°C.
EXAMPLE - 4
28 parts of aromatic amine was dissolved in 100 parts of EPN at 100°C by constant stirring and then added 20%BMI. The stirring was continued to get a clear melt by raising the temperature to 120°C . Then the resultant melt was cured at 120°C for 1 hr, 150°C for 2 hrs followed by a final cure at 220°C for 2 hr. The Tg measured by DSC technique was found to be 228°C.
EXAMPLE -5
28 parts of aromatic amine was dissolved in 100 parts of EPN at 100°C by constant stirring and then added 30%BMI. The stirring was continued to get a clear melt by raising the temperature to 120°C . Then the resultant melt was cured at 120°C for 1 hr, 150°C for 2 hrs followed by a final cure at 220°C for 4hr. The Tg measured by DSC technique was found to be 232°C.
EXAMPLE - 6
Thermal stability of the cured products were determined using thermogravimetric analysis technique (TGA) which gives information related to the weight loss of the material with respect to temperature (Thermal decomposition). The thermograms showed enhanced thermal stability when compared to unmodified Epoxy systems.
It was found that the addition of higher percentage of BMI to the Epoxy novolac-Amine system and curing in a step wise schedule enhanced the glass transition temperature and the thermal stability. It was also found that addition of more than 35% of BMI causes phase separation problems due to the solubility parameters.
The novelty of the present invention lies in the preparation of a new material, with a new combination of materials, having better properties such as high Tg and high thermal stability. The drawbacks previously referred to have been obviated.
The inventive steps are in choosing a new combination of materials which result in a blend having tailor-made properties such as high glass transition temperature, high thermal stability and good processing window.
The main advantages of the process of the present invention are
1. Enhancement of Tg (Glass transition temperature)
2. Increase in thermal stability
3. Reduction in moisture uptake
4. Good processing window (viscosity)
5. Preparation of a new material with tailor made properties to suit the
requirements
6. Preparation of a new material within a short time using small amounts
of Bismaleimide(BMI) which has resulted in better properties

We Claim:
1. A process for the preparation of a novel thermosetting polymer useful for
engineering applications which comprises; dissolving 20-35 weight percentage of
one or more aromatic amines in 100 weight percentage of Epoxy novolac under
constant stirring at a temperature in the range 70-120°C, adding 2-35% of
aromatic amine based Bismaleimide to the resultant solution maintained at a
temperature in the range of 70-120°C under constant stirring to obtain a clear
melt, subjecting the resultant clear melt so obtained to a multi-step curing at
temperatures in the range of 100 - 240°C for a period of at least 4 hrs, to obtain
the product.
2. The process as claimed in claim 1 where in the aromatic used is preferably a
diamine.
3. The process as claimed in claims 1 and 2 where in the multi-step curing is
effected at a temperature in the range 100 - 130°C for at least 1 hr, followed by
curing at a temperature in the range of 150-200°C for at least 1 hr and final curing
at a temperature in the range of 200 - 240°C for at least 1 hr.
4. A process for the preparation of a novel thermosetting polymer useful for
engineering applications substantially as herein described with reference to the
examples.

Documents:

163-del-2000-abstract.pdf

163-del-2000-claims.pdf

163-del-2000-correspondence-others.pdf

163-del-2000-correspondence-po.pdf

163-del-2000-description (complete).pdf

163-del-2000-form-1.pdf

163-del-2000-form-19.pdf

163-del-2000-form-2.pdf

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Patent Number

218304

Indian Patent Application Number

163/DEL/2000

PG Journal Number

24/2008

Publication Date

13-Jun-2008

Grant Date

31-Mar-2008

Date of Filing

25-Feb-2000

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	AVADHANAM VANAJA, S.R.F.	DEPUTY DIRECTOR, HEAD, FRP PILOT PLANT UNIT NATIONAL AEROSPACE LABORATORIES BANGALORE-560 017 INDIA.
2	RAJA MANURI VENKATA GOPAAKRISHNA RAO	DEPUTY DIRECTOR, HEAD, FRP PILOT PLANT UNIT NATIONAL AEROSPACE LABORATORIES BANGALORE-560 017 INDIA.

PCT International Classification Number

C08F 8/08

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA