Title of Invention	A process for synthesis of a new tetra glycidyl paraphenylene diamine (TGPPD) epoxy resin
Abstract	This invention relates to a process for the synthesis of a new epoxy resin. This invention particularly relates to a process for the preparation of novel epoxy resin namely Tetra Glycidyl Para Phenylene Diamine (TGPPD), which comprises reacting Para Phenylene Diamine (PPD) and Epichlorohydrin (ECH) in the presence of a quarternary ammonium salt as a catalyst. The epoxy resin so obtained possesses low viscosity as compared to many commercially available multifunctional epoxy resins. In addition the resin yields (a) high glass transition temperature (Tg) matrix when hot cured with diamino diphenyl methane (DDM) hardener. It also gives a higher Tg even when cured with an ambient cure hardener followed by post curing.

Title of Invention

A process for synthesis of a new tetra glycidyl paraphenylene diamine (TGPPD) epoxy resin

Abstract

This invention relates to a process for the synthesis of a new epoxy resin. This invention particularly relates to a process for the preparation of novel epoxy resin namely Tetra Glycidyl Para Phenylene Diamine (TGPPD), which comprises reacting Para Phenylene Diamine (PPD) and Epichlorohydrin (ECH) in the presence of a quarternary ammonium salt as a catalyst. The epoxy resin so obtained possesses low viscosity as compared to many commercially available multifunctional epoxy resins. In addition the resin yields (a) high glass transition temperature (Tg) matrix when hot cured with diamino diphenyl methane (DDM) hardener. It also gives a higher Tg even when cured with an ambient cure hardener followed by post curing.

Full Text	The present invention relates to a process for the synthesis of a new epoxy resin. This invention particularly relates to a process for the preparation of new epoxy resin namely tetraglycidyl paraphenylene diamine epoxy resin. The resin prepared is useful as matrix resin for advanced composites and has potential as a coating and structural adhesive. The resin prepared by the process possesses low viscosity ("6000 centi poise at 25°C ) at the same time yielding a high Tg ("225 ° C) matrix when cured with hot cure DDM hardener. A Tg of 185°C matrix was also obtained when cured with ambient cure hardener (HY 5052 - coded ciba Geigy) followed by post cure. The low viscosity characteristic of this resin facilitates easy wetting (impregnation) of the fibres ( glass, carbon etc.) during composite moulding and fabrication operations. This ease of wetting further leads to enhancement to interlaminar shear and compression properties which are highly desirable design requirements for costeffective and efficient designing of structural composites. In comparison the multifunctional epoxy resins which are usually known exhibiting similar high Tg values have very high viscosities ( far above 10,000 centi poise 25°C). The high viscosity of these resins poses processing difficultes ( wetting, spreading ) while making the composite components out of it. Hence there is a great demand for easily processable low viscous, high Tg and high toughness epoxy resins. Therefore the main objective of the present invention is to provide a process for the synthesis of a novel low viscous multifunctional epoxy resin. Another objective of the present invention is to provide a process for the synthesis of novel epoxy namely Tetra Glycidyl Para Phenylene Diamine (TGPPD). With the above mentioned objectives we undertook R & D program to synthesis a new tetrafunctional epoxy resin namely Tetraglycidyl Paraphenylene Diamine (TGPPD) epoxy resin with a low viscosity to offer processing characteristics superior to those of commercially available resins. Further it has been found that this new epoxy resin prepared when modified with thermoplastics additives such as ABS/PC (Acrylonitrile-Butadiene-Styrene/Polycarbonate) copolymer and polyimide yielded high toughness values while retaining its high Tg values. Accordingly, the present invention provides a process for the preparation of a new epoxy resin, tetraglycidyl paraphenylene diamine (TGPPD) of the formula 3 shown in the drawing accompanying this specification, which comprises: i) reacting paraphenylene diamine of the formula 1 shown in the drawing accompanying the specification and epichlohydrin of the formula 2 shown in the drawing accompanying the specification, at a temperature in the range of 70°C to 90°C, for a period in the range of 2 to 4 hours in the presence of a tetra butyl ammonium iodide (TBAI) catalyst, ii) dehydrohalogenating the resultant chlorohydrin intermediate by reacting the caustic soda solution, iii) filtering to remove the salt formed at step (ii), iv) distilling the obtained filtrate to remove the excess (unreacted) epichlorohydrin under reduced pressure, v) washing the resultant resin with distilled water repeatedly until netural pH is obtained, vi) extracting the resin with dichloromethane, and vii) finally distilling the solvent under reduced pressure to yield the pure pale brown tetraglycidyl paraphenyiene diamine (TGPPD) epoxy resin. In a preferred embodiment of the invention, the para phenylene diamine used may be the one which is recrystallised from boiling water. In another embodiment of the invention, the epichlorhydrin used is the one freshly distilled. The ratio of the amount of para phenylene diamine and epichlohydrin employed may be in the ratio of 1 : 20 . moles. The dehrohalogenation may be effected by the dropwise addition of stoichiometric quantity of caustic solution ( 40% aqueous solution of sodium hydroxide) at about 40°C for a period of one hour under continuous stirring. The yield of the resin was "94.5%. the viscosity of the resin was "6000 centi poise at 25°C. The pure TGPPD resin was characterized by infrared Spectroscopy (IR), Proton Fourier Transform Nuclear Magnetic Resonance Spectroscopy ( H'FTNMR), Thermogravimetric analysis (TGA), Viscosity determination, Epoxide Equivalent weight ( "108) determination etc. Similar results were obtained for different batches of resin. The TGPD epoxy resin prepared by the process of the invention having the formula 3 (molecular formula C18H24N2O4), has IR as shown in fig - 4, NMR as shown in fig - 5 and molecular weight 338. The details of the invention are described in the following examples which are provided by way of illustrations only and therefore should not be construed to limit the scope of the invention. Example -1 In this experiment the TGPPD resin was synthesized by reacting 1 mole of PPD and 4 moles of ECH. The reactants were heated to 80°C for 4 hours in the presence of TBAI catalyst. The reaction mixture was then cooled to 40°C and stoichiometric quantity of caustic solution ( 40% aq. Solution of sodium hydroxide) was added dropwise over a period of 1 hour. The precipitated sodium chloride salt was subsequently filtered and the reaction mixture washed with distilled water repeatedly until the neutral pH is obtained. Finally, the resin was extracted with dichloromethane. The pure TGPPD resin was obtained after distilling out the solvent at reduced pressure. The yield was about 95% and the viscosity was about 8000 centi poise at 25°C. The epoxide equivalent weight of the resin was "108. However this viscosity was found to be higher than desired. Example - 2 In this experiment one mole of PPD and 10 moles of ECH were reacted at 80°C for 4 hours in the presence of TBAI catalyst. Then the reaction mixture was cooled to 40°C and stoichiometric quantity of caustic solution ( 40% aq. Solution of sodium hydroxide) was added dropwise over a period of 1 hour. The precipitated sodium chloride salt was filtered and the reaction mixture was washed with distilled water repeatedly until the neutral pH is obtained. Finally, the resin was extracted with dichloromethane. The pure TGPPD resin was obtained after distilling out the solvent under reduced pressure. The yield was about 95% and the viscosity was about 7000 centi poise at 25°C. The epoxide equivalent weight of the resin was "108. Example - 3 This experiment was carried out by taking one mole of PPD and 15 moles of ECH and then reacting them at 80°C for 4 hours in the presence of TBAI catalyst. Then the reaction mixture was cooled to 40°C and" stoichiometric quantity of caustic solution (40% aq. Solution of sodium hydroxide) was added dropwise over a period of 1 hour. The precipitated sodium chloride salt was filtered and the reaction mixture was washed with distilled water repeatedly until the neutral pH is obtained. Finally, the resin was extracted with dichloromethane. The pure TGPPD resin was obtained after distilling out the solvent under reduced pressure. The yield was about 95% and the viscosity has further reduced to 6500 centi poise at 25°C. The epoxide equivalent weight of the resin was "108. Example - 4 In this experiment one mole of PPD and 20 moles of ECH were reacted at 80°C for 4 hours in the presence of TBAI catalyst. Then the reaction mixture was cooled to 40°C and stoichiometric quantity of caustic solution ( 40% aq. Solution of sodium hydroxide) was added dropwise over a period of 1 hour. The precipitated sodium chloride salt was filtered and the reaction mixture was washed with distilled water repeatedly until the neutral pH is obtained. Finally, the resin was obtained after distilling out the solvent under reduced pressure. The yield was about 95% and the viscosity was about 6000 centi poise at 25°C. The epoxide equivalent weight of the resin was "108. Example - 5 The experiment was performed by reacting one mole of PPD and 20 mole of ECH at 80°C for 4 hours in the presence of TBAI catalyst. Then the reaction mixture was cooled to 40°C and stoichiometric quantity of caustic solution (40 % aq. Solution of sodium hydroxide) was added dropwise over a period of 1 hour. The precipitated sodium chloride salt was filtered and the reaction mixture was washed with distilled water repeatedly until the neutral pH is obtained. Finally, the resin was extracted with dichloromethane. The pure TGPPD resin was obtained after distilling out the solvent under reduced pressure. The yield obtained was about 95% and the viscosity was about 6000 centi poise at 25°C. The epoxide equivalent weight of the resin was "108. The above examples clearly indicate that the chemically pure TGPPD resin with low viscosity ( "6000 centi poise at 25°C) can be obtained from recrystallised PPD and freshly distilled ECH (1 : 20 mole ratio) in the presence of TBAI catalyst, using dichloromethane as a solvent for extracting the resin. By this process it has been possible to prepare a low viscosity, high Tg TGPPD resin reproducibly. We Claim: 1. A process for the preparation of a new epoxy resin tetraglycidyl paraphenylene diamine (TGPPD) of the formula 3 shown in the drawing accompanying this specification, which comprises: i) reacting paraphenylene diamine of the formula 1 shown in the drawing accompanying the specification and epichlohydrin of the formula 2 shown in the drawing accompanying the specification, at a temperature in the range of 70°C to 90°C, for a period in the range of 2 to 4 hours in the presence of a tetra butyl ammonium iodide (TBAI) catalyst, ii) dehydrohalogenating the resultant chlorohydrin intermediate by reacting the caustic soda solution, iii) filtering to remove the salt formed at step (ii), iv) distilling the obtained filtrate to remove the excess (unreacted) epichlorohydrin under reduced pressure, v) washing the resultant resin with distilled water repeatedly until netural pH is obtained, vi) extracting the resin with dichloromethane, and vii) finally distilling the solvent under reduced pressure to yield the pure pale brown tetraglycidyl paraphenylene diamine (TGPPD) epoxy resin. A process as claimed in claim 1 wherein the para phenylene diamine used is the one which is recrystallised from boiling water. A process as claimed in claims 1-2 wherein the ratio of the amount of para phenylene diamaine and epichlohydrin employed is 1 : 20. moles. 4. A process as claimed in claims 1-4 wherein the dehydrohalogenation is effected by dropwise addition of stoichiometric quantity of caustic soda solution (40% aqueous solution of sodium hydroxide ) at about 40 degree C for a period of one hour under continuous stirring. 5. A process for the preparation of a new epoxy resin, tetraglycidyl paraphenylene diamine (TGPPD) of the formula 3 shown in the drawing accompanying this specification substantially as hereindescribed with reference to the examples.

Full Text

The present invention relates to a process for the synthesis of a new epoxy resin. This invention particularly relates to a process for the preparation of new epoxy resin namely tetraglycidyl paraphenylene diamine epoxy resin.
The resin prepared is useful as matrix resin for advanced composites and has potential as a coating and structural adhesive. The resin prepared by the process possesses low viscosity ("6000 centi poise at 25°C ) at the same time yielding a high Tg ("225 ° C) matrix when cured with hot cure DDM hardener. A Tg of 185°C matrix was also obtained when cured with ambient cure hardener (HY 5052 - coded ciba Geigy) followed by post cure.
The low viscosity characteristic of this resin facilitates easy wetting (impregnation) of the fibres ( glass, carbon etc.) during composite moulding and fabrication operations. This ease of wetting further leads to enhancement to interlaminar shear and compression properties which are highly desirable design requirements for costeffective and efficient designing of structural composites.
In comparison the multifunctional epoxy resins which are usually known exhibiting similar high Tg values have very high viscosities ( far above 10,000 centi poise 25°C). The high viscosity of these resins poses processing difficultes ( wetting, spreading ) while making the composite components out of it. Hence there is a great demand for easily processable low viscous, high Tg and high toughness epoxy resins.
Therefore the main objective of the present invention is to provide a process for the synthesis of a novel low viscous multifunctional epoxy resin.

Another objective of the present invention is to provide a process for the synthesis of novel epoxy namely Tetra Glycidyl Para Phenylene Diamine (TGPPD).
With the above mentioned objectives we undertook R & D program to synthesis a new tetrafunctional epoxy resin namely Tetraglycidyl Paraphenylene Diamine (TGPPD) epoxy resin with a low viscosity to offer processing characteristics superior to those of commercially available resins.
Further it has been found that this new epoxy resin prepared when modified with thermoplastics additives such as ABS/PC (Acrylonitrile-Butadiene-Styrene/Polycarbonate) copolymer and polyimide yielded high toughness values while retaining its high Tg values.
Accordingly, the present invention provides a process for the preparation of a new epoxy resin, tetraglycidyl paraphenylene diamine (TGPPD) of the formula 3 shown in the drawing accompanying this specification, which comprises:
i) reacting paraphenylene diamine of the formula 1 shown in the drawing accompanying the specification and epichlohydrin of the formula 2 shown in the drawing accompanying the specification, at a temperature in the range of 70°C to 90°C, for a period in the range of 2 to 4 hours in the presence of a tetra butyl ammonium iodide (TBAI) catalyst, ii) dehydrohalogenating the resultant chlorohydrin intermediate by reacting
the caustic soda solution, iii) filtering to remove the salt formed at step (ii),

iv) distilling the obtained filtrate to remove the excess (unreacted)
epichlorohydrin under reduced pressure, v) washing the resultant resin with distilled water repeatedly until netural pH
is obtained, vi) extracting the resin with dichloromethane, and vii) finally distilling the solvent under reduced pressure to yield the pure pale
brown tetraglycidyl paraphenyiene diamine (TGPPD) epoxy resin.
In a preferred embodiment of the invention, the para phenylene diamine used may be the one which is recrystallised from boiling water.
In another embodiment of the invention, the epichlorhydrin used is the one freshly distilled. The ratio of the amount of para phenylene diamine and epichlohydrin employed may be in the ratio of 1 : 20 . moles. The dehrohalogenation may be effected by the dropwise addition of stoichiometric quantity of caustic solution ( 40% aqueous solution of sodium hydroxide) at about 40°C for a period of one hour under continuous stirring.
The yield of the resin was "94.5%. the viscosity of the resin was "6000 centi poise at 25°C.
The pure TGPPD resin was characterized by infrared Spectroscopy (IR), Proton Fourier Transform Nuclear Magnetic Resonance Spectroscopy ( H'FTNMR), Thermogravimetric analysis (TGA), Viscosity determination, Epoxide Equivalent weight ( "108) determination etc. Similar results were obtained for different batches of resin.

The TGPD epoxy resin prepared by the process of the invention having the formula 3 (molecular formula C18H24N2O4), has IR as shown in fig - 4, NMR as shown in fig - 5 and molecular weight 338.
The details of the invention are described in the following examples which are provided by way of illustrations only and therefore should not be construed to limit the scope of the invention.
Example -1
In this experiment the TGPPD resin was synthesized by reacting 1 mole of PPD and 4 moles of ECH. The reactants were heated to 80°C for 4 hours in the presence of TBAI catalyst. The reaction mixture was then cooled to 40°C and stoichiometric quantity of caustic solution ( 40% aq. Solution of sodium hydroxide) was added dropwise over a period of 1 hour. The precipitated sodium chloride salt was subsequently filtered and the reaction mixture washed with distilled water repeatedly until the neutral pH is obtained. Finally, the resin was extracted with dichloromethane. The pure TGPPD resin was obtained after distilling out the solvent at reduced pressure. The yield was about 95% and the viscosity was about 8000 centi poise at 25°C. The epoxide equivalent weight of the resin was "108. However this viscosity was found to be higher than desired.
Example - 2
In this experiment one mole of PPD and 10 moles of ECH were reacted at 80°C for 4 hours in the presence of TBAI catalyst. Then the reaction mixture was cooled to 40°C and stoichiometric quantity of caustic solution ( 40% aq. Solution of sodium hydroxide) was added dropwise over a period of 1 hour. The

precipitated sodium chloride salt was filtered and the reaction mixture was washed with distilled water repeatedly until the neutral pH is obtained. Finally, the resin was extracted with dichloromethane. The pure TGPPD resin was obtained after distilling out the solvent under reduced pressure. The yield was about 95% and the viscosity was about 7000 centi poise at 25°C. The epoxide equivalent weight of the resin was "108.
Example - 3
This experiment was carried out by taking one mole of PPD and 15 moles of ECH and then reacting them at 80°C for 4 hours in the presence of TBAI catalyst. Then the reaction mixture was cooled to 40°C and" stoichiometric quantity of caustic solution (40% aq. Solution of sodium hydroxide) was added dropwise over a period of 1 hour.
The precipitated sodium chloride salt was filtered and the reaction mixture was washed with distilled water repeatedly until the neutral pH is obtained. Finally, the resin was extracted with dichloromethane. The pure TGPPD resin was obtained after distilling out the solvent under reduced pressure. The yield was about 95% and the viscosity has further reduced to 6500 centi poise at 25°C. The epoxide equivalent weight of the resin was "108.
Example - 4
In this experiment one mole of PPD and 20 moles of ECH were reacted at 80°C for 4 hours in the presence of TBAI catalyst. Then the reaction mixture was cooled to 40°C and stoichiometric quantity of caustic solution ( 40% aq. Solution of sodium hydroxide) was added dropwise over a period of 1 hour. The

precipitated sodium chloride salt was filtered and the reaction mixture was washed with distilled water repeatedly until the neutral pH is obtained. Finally, the resin was obtained after distilling out the solvent under reduced pressure. The yield was about 95% and the viscosity was about 6000 centi poise at 25°C. The epoxide equivalent weight of the resin was "108.
Example - 5
The experiment was performed by reacting one mole of PPD and 20 mole of ECH at 80°C for 4 hours in the presence of TBAI catalyst. Then the reaction mixture was cooled to 40°C and stoichiometric quantity of caustic solution (40 % aq. Solution of sodium hydroxide) was added dropwise over a period of 1 hour. The precipitated sodium chloride salt was filtered and the reaction mixture was washed with distilled water repeatedly until the neutral pH is obtained. Finally, the resin was extracted with dichloromethane. The pure TGPPD resin was obtained after distilling out the solvent under reduced pressure. The yield obtained was about 95% and the viscosity was about 6000 centi poise at 25°C. The epoxide equivalent weight of the resin was "108.
The above examples clearly indicate that the chemically pure TGPPD resin with low viscosity ( "6000 centi poise at 25°C) can be obtained from recrystallised PPD and freshly distilled ECH (1 : 20 mole ratio) in the presence of TBAI catalyst, using dichloromethane as a solvent for extracting the resin. By this process it has been possible to prepare a low viscosity, high Tg TGPPD resin reproducibly.

We Claim:
1. A process for the preparation of a new epoxy resin tetraglycidyl paraphenylene diamine (TGPPD) of the formula 3 shown in the drawing accompanying this specification, which comprises:
i) reacting paraphenylene diamine of the formula 1 shown in the drawing accompanying the specification and epichlohydrin of the formula 2 shown in the drawing accompanying the specification, at a temperature in the range of 70°C to 90°C, for a period in the range of 2 to 4 hours in the presence of a tetra butyl ammonium iodide (TBAI) catalyst,
ii) dehydrohalogenating the resultant chlorohydrin intermediate by reacting the caustic soda solution,
iii) filtering to remove the salt formed at step (ii),
iv) distilling the obtained filtrate to remove the excess (unreacted) epichlorohydrin under reduced pressure,
v) washing the resultant resin with distilled water repeatedly until netural pH is obtained,
vi) extracting the resin with dichloromethane, and
vii) finally distilling the solvent under reduced pressure to yield the pure pale brown tetraglycidyl paraphenylene diamine (TGPPD) epoxy resin. A process as claimed in claim 1 wherein the para phenylene diamine used is the one which is recrystallised from boiling water.
A process as claimed in claims 1-2 wherein the ratio of the amount of para phenylene diamaine and epichlohydrin employed is 1 : 20. moles.

4. A process as claimed in claims 1-4 wherein the dehydrohalogenation is effected by dropwise addition of stoichiometric quantity of caustic soda solution (40% aqueous solution of sodium hydroxide ) at about 40 degree C for a period of one hour under continuous stirring.
5. A process for the preparation of a new epoxy resin, tetraglycidyl paraphenylene diamine (TGPPD) of the formula 3 shown in the drawing accompanying this specification substantially as hereindescribed with reference to the examples.

Documents:

2307-del-1996-abstract.pdf

2307-del-1996-claims.pdf

2307-del-1996-complete specification (granted).pdf

2307-del-1996-correspondence-others.pdf

2307-del-1996-correspondence-po.pdf

2307-del-1996-description (complete).pdf

2307-del-1996-drawings.pdf

2307-del-1996-form-1.pdf

2307-del-1996-form-2.pdf

2307-del-1996-form-4.pdf

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Patent Number

195194

Indian Patent Application Number

2307/DEL/1996

PG Journal Number

38/2008

Publication Date

19-Sep-2008

Grant Date

09-Mar-2007

Date of Filing

25-Oct-1996

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	Kandasamy Natarajan, Lecturer	R.V. College of Engineering, Bangalore-560017,India.
2	Dr. Adoni Padma , Scientist	National Aerospace Laboratories, Bangalore-560017,India.
3	Dr. Raja Manuri Venkata Gopala Krishna Rao, Scientist	National Aerospace Laboratories, Bangalore-560017,India.

PCT International Classification Number

C08G 59/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA