Process for preparation of self healing microcapsules

Abstract

The present invention disclosed a process for the preparation of microcapsules containing epoxy resin which comprises water-insoluble and/or water-soluble components prepared by in-situ polymerization using non-aqueous continuous phase which acts as healing agents for the micro-cracks when embedded in composite structures.

Claims

1. A process for the preparation of self-healing microcapsules with polyurethane as capsule wall material prepared by in-situ polymerization using non-aqueous continuous phase comprising the steps of: a) preparing a mixture of epoxy components to be encapsulated and polyisocyante; b) preparing a solution of diol or polyol with a cross-linker in aliphatic hydrocarbon; c) dispersing the mixture of step a) in a solution of a stabilizer and a catalyst in an aliphatic hydrocarbon; d) adding the solution of step (b) drop wise to the dispersion of step c) under agitation followed by treatment with anti-agglomerating agent to obtain microcapsules; and e) filtering and/or centrifuging, washing the microcapsules as obtained in step (d), with the aliphatic hydrocarbon and drying the microcapsules under vacuum at ambient temperature to obtain microcapsules with polyurethane as capsule wall material.

2. The process as claimed in claim 1, wherein said polyisocyante is selected from aromatic polyisocyanates, aliphatic polyisocyanates, or mixtures thereof and said aromatic polyisocyanate is selected from the group consisting of 2,4- and 2,6-toluene diisocyanate (TDI), naphthalene diisocyanate, diphenyl methane diisocyanate, triphenyl methane-p,pp-trityltriisocyanate, polymethylene polyphenyleneisocyanate, 2,4,4-diphenylether triisocyanate, 3,3-dimethyl-4,4-diphenyl diisocyanate, 3,3-dimethoxy-4,4diphenyl diisocyanate, triphenylmethane 4,4, 4 triisocyanate, and mixtures thereof and said aliphatic polyisocyanate is selected from the group consisting of dicyclohexylmethane 4,4-diisocyanate, hexamethylene1,6-diisocyanate (HMDI), isophoronediisocyanate (IPDI), trimethyl-hexamethylenediisocyanate, trimethylenediisocyanate, propylene-1,2-diisocyanate, butylene1,2-diisocyanate and mixtures thereof.

3. The process as claimed in claim 1, wherein said diol or polyol is selected from ethylene glycol, diethylene glycol, propylene glycol, 1,4-butane diol, 1,4 hexane diol, dipropylene glycol, cyclohexyl 1,4 dimethanol, 1,8 octane diol, 2,methyl 2,4 pentane diol (MPD), 1,3-propane diol, poly (ethylene glycols), poly (propylene glycols) or poly(tetra methylene glycols).

4. The process as claimed in claim 1, wherein said cross-linker is selected from the group consisting of butane-1,2,3-triol, butane-1,2,4-triol, 2,2-dihydromethyl-1,3propane diol, castor oil, caprolactone-based triols, 2-hydroxy methyl-1,3-propane diol, trimethylol propane (TMP), trimethylol ethane (TME) and mixtures thereof.

5. The process as claimed in claim 1, wherein said catalyst is selected from the group consisting of N, N dimethylaminoethanol, N, N-dimethylcyclohexylamine, bis[2-(N,Ndimethylamino)ethyl]ether, N,N-dimethylacetylamine, diaminobicyclooctane, stannous octoate, dibutyltindilaurate (DBTDL) and mixtures thereof.

6. A process for the preparation of self-healing microcapsules with epoxy as capsule wall material prepared by in-situ polymerization using non-aqueous continuous phase comprising the steps of: a) dispersing epoxy components to be encapsulated in a solution of a stabilizer in an aliphatic hydrocarbon; b) preparing a solution of polyamine alone or optionally along with another polyamine in aliphatic hydrocarbon; c) adding solution prepared in step (b) drop wise to the dispersion of step (a) under agitation followed by treatment with anti-agglomerating agent to obtain microcapsules; and d) filtering and/or centrifuging, washing the microcapsules, with the aliphatic hydrocarbon and drying the microcapsules under vacuum at ambient temperature to obtain microcapsules with epoxy as capsule wall material.

7. The process as claimed in claim 1 or 6, wherein said stabilizer is selected from non-ionic polymeric surfactants having repeating hydrophilic and hydrophobic units, preferably polymeric non-ionic surfactant, more preferably Hydrophilic Lipophilic Balance (HLB) between 4 and 13.

8. The process as claimed in claim 1 or 6, wherein said epoxy component is selected from the group consisting of diglycidyl ether of bisphenol A, diglycidyl ethers of bisphenol F, epoxy phenol novolacs (EPN), epoxy cresol novolacs (ECN), diglycidyl ether of butane diol(Butyl dioldiglycidyl ether), 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate, triglycidyl-p-aminophenol, N,N,N,N-tetraglycidyl-4,4-methylenebis benzylamine, 4-glycidyloxy-N,N-di-glycidyl aniline, 1.1.2.2-(p-hydroxyphenol) ethane based epoxy resin, ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, polyethyleneglycol diglycidyl ether, propylene glycol diglycidyl ether and glycerol polyglycidyl ether.

9. The process as claimed in claim 6, wherein said polyamine is selected from the group consisting of polyfunctional Aziridine PZ-33, PZ-28 (from Poly Aziridine L.L.C. NJ, USA), diethylenetriamine (DETA), triethylenetetraamine (TETA), tetraethylenepentamine, 2,4,4-triaminodiphenylether, bis(hexamethylene) triamine, 1,4,5,8-tetraamino anthraquinone, ethylene diamine (EDA), trimethylenedipiperidine (TMDP), guanidine carbonate (GUCA), phenylenediamine, toluene diamine, pentamethylene hexamine, 1,6-hexamethylene diamine, 2,4-diamino-6-methyl-1,3,5 triazine 1,2-diaminocyclohexane, 4,4-diaminodiphenylmethane, 1,5-diaminonaphthalene-isophoronediamine, diamino propane, diaminobutane and mixtures thereof.

10. The process as claimed in claim 1 or 6, wherein said non-aqueous continuous medium for microencapsulation used as continuous phase may be selected from aliphatic hydrocarbon of the general formula C.sub.nH.sub.2n+2 where n can be between 6 to 16 and is selected from hexane, octane, decane, isooctane, dodecane, hexadecane, superior kerosene, paraffin oil, white mineral oil or suitable mixtures thereof.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIGS. 1(a)-1(d): Rupture test of microcapsules. FIG. 1(a): few mg of microcapsules were taken on slide; FIG. 1(b): one drop of hardener was added; FIG. 1(c): another slide was put on above slide and finger pressure was applied; FIG. 1(d): after 2 hours it was observed that slides cannot be separated.

(2) FIGS. 2(a)-2(f): SEM images of microcapsules. FIG. 2(a) microcapsules prepared as per Example 1; FIG. 2(b) microcapsules prepared as per Example 4; FIG. 2(c) microcapsules prepared as per Example 5; FIG. 2(d) microcapsules prepared as per Example 6; FIG. 2(e) microcapsules prepared as per Example 11; FIG. 2(f) microcapsules prepared as per Example 13.

(3) FIGS. 3(a)-3(b): Optical images of microcapsules. FIG. 3(a) microcapsules prepared as per Example 2; FIG. 3(b) microcapsules prepared as per Example 3.

DETAILED DESCRIPTION OF THE INVENTION

(4) There are reports in the literature which describe microencapsulation of epoxy resin which is water-insoluble and hence aqueous continuous phase can be used for the preparation of the same. However as the epoxy formulation described herein contain water-soluble component, the processes described in the literature is not suitable and hence the instant invention proposes a novel process that suits the preparation of microcapsules containing water soluble components.

(5) In the view of above, the instant invention provides a process for the preparation of microcapsules containing epoxy resin comprising water-insoluble and/or water-soluble components which acts as healing agents for the micro-cracks when embedded in composite structures.

(6) The present invention provides a process for the preparation of self-healing microcapsules with polyurethane as capsule wall material prepared by in-situ polymerization using non-aqueous continuous phase comprising the steps of: a) preparing a mixture of water soluble and/or water insoluble epoxy components to be encapsulated and polyisocyante; b) preparing a solution of diol or polyol with a cross-linker in aliphatic hydrocarbon; c) dispersing the mixture of step a) in a solution of a stabilizer/surfactant and a catalyst selected from amino or organometallic compounds in an aliphatic hydrocarbon; d) adding the solution of step (b) drop wise to the dispersion of step c) under agitation followed by treatment with anti-agglomerating agent to obtain microcapsules; and e) filtering and/or centrifuging, washing the microcapsules, with the aliphatic hydrocarbon and drying the microcapsules under vacuum at ambient temperature.

(7) Polyisocyante used is selected from aromatic polyisocyanates or aliphatic polyisocyanates, or mixtures thereof, wherein said aromatic polyisocyanate is selected from the group consisting of 2,4- and 2,6-toluene diisocyanate (TDI), naphthalene diisocyanate, diphenyl methane diisocyanate, triphenyl methane-p,pp-trityltriisocyanate, polymethylene polyphenyleneisocyanate, 2,4,4-diphenylether triisocyanate, 3,3-dimethyl-4,4-diphenyl diisocyanate, 3,3-dimethoxy-4,4diphenyl diisocyanate, triphenylmethane 4,4, 4 triisocyanate, and mixtures thereof and said aliphatic polyisocyanate is selected from the group consisting of dicyclohexylmethane 4,4-diisocyanate, hexamethylene1,6-diisocyanate (HMDI), isophoronediisocyanate (IPDI), trimethyl-hexamethylenediisocyanate, trimethylenediisocyanate, propylene-1,2-diisocyanate, butylene1,2-diisocyanate, and mixtures thereof.

(8) Diol or polyol used is selected from the group consisting of ethyleneglycol, diethylene glycol, propylene glycol, 1,4-butane diol, 1,4 hexane diol, dipropylene glycol, cyclohexyl 1,4 dimethanol, 1,8 octane diol, 2,methyl 2,4 pentane diol (MPD), 1,3-propane diol, poly (ethylene glycols), poly (propylene glycols) or poly(tetra methylene glycols).

(9) Cross-linker used is selected from butane-1,2,3-triol, butane-1,2,4-triol, 2,2-dihydromethyl-1,3propane diol, castor oil, caprolactone-based triols, 2-hydroxy methyl-1,3-propane diol, trimethylol propane (TMP), trimethylol ethane (TME) and mixtures thereof.

(10) Catalyst used is N, N dimethylaminoethanol, N, N-dimethylcyclohexylamine, bis[2-(N,N dimethylamino) ethyl] ether, N, N-dimethylacetylamine, diaminobicyclooctane, stannous octoate, dibutyltindilaurate (DBTDL) and mixtures thereof.

(11) The present invention provides a process for the preparation of self-healing microcapsules with epoxy as capsule wall material prepared by in-situ polymerization using non-aqueous continuous phase comprising the steps of: a) dispersing water soluble and/or water insoluble epoxy components to be encapsulated in a solution of a stabilizer in an aliphatic hydrocarbon; b) preparing a solution of polyamine alone or optionally along with another polyamine in aliphatic hydrocarbon; c) adding solution prepared in step (b) drop wise to the dispersion of step a) under agitation followed by treatment with anti-agglomerating agent to obtain microcapsules; and d) filtering and/or centrifuging, washing the microcapsules, with the aliphatic hydrocarbon and drying the microcapsules under vacuum at ambient temperature.

(12) Stabilizer used is selected from non-ionic polymeric surfactants having repeating hydrophilic and hydrophobic units such as polymeric non-ionic surfactant, preferably with Hydrophilic Lipophilic Balance (HLB) between 4 and 13.

(13) Epoxy component used is water soluble and water insoluble and selected from diglycidyl ether of bisphenol A, diglycidyl ethers of bisphenol F, epoxy phenol novolacs (EPN), epoxy cresol novolacs (ECN), diglycidyl ether of butane diol (Butyl dioldiglycidyl ether), 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate, triglycidyl-p-aminophenol, N,N,N,N-tetraglycidyl-4,4-methylenebis benzylamine, 4-glycidyloxy-N,N-di-glycidyl aniline, 1.1.2.2-(p-hydroxyphenol) ethane based epoxy resin, ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, polyethyleneglycol diglycidyl ether, propylene glycol diglycidyl ether or glycerol polyglycidyl ether.

(14) Polyamine used is selected from polyfunctional Aziridine PZ-33, PZ-28 (from Poly Aziridine L.L.C. NJ, USA), diethylenetriamine (DETA), triethylenetetraamine (TETA), tetraethylenepentamine, 2,4,4-triaminodiphenylether, bis(hexamethylene) triamine, 1,4,5,8-tetraamino anthraquinone, ethylene diamine (EDA), trimethylenedipiperidine (TMDP), guanidine carbonate (GUCA), phenylenediamine, toluene diamine, pentamethylene hexamine, 1,6-hexamethylene diamine, 2,4-diamino-6-methyl-1,3,5 triazine 1,2-diaminocyclohexane, 4,4-diaminodiphenylmethane, 1,5-diaminonaphthalene-isophoronediamine, diamino propane, diaminobutane and mixtures thereof.

(15) Non-aqueous continuous medium for microencapsulation used as continuous phase may be selected from aliphatic hydrocarbon of the general formula C.sub.nH.sub.2n+2 where n can be between 6 to 16 and is selected from hexane, octane, decane, isooctane, dodecane, hexadecane, superior kerosene, paraffin oil, white mineral oil or suitable mixtures thereof.

(16) The microcapsules of the invention thus obtained have a particle size ranging from 1 to 100 microns.

(17) The instant invention provides self-healing microcapsules of epoxy comprising water-insoluble and/or water-soluble components prepared by in-situ polymerization using non-aqueous continuous phase.

(18) To check if microcapsules containing epoxy resin break with pressure characterization experiment is carried out. Few mg of microcapsules from Example 1 containing mixture of water insoluble and soluble epoxy resin were taken on microscope glass slide along with few mg of hardener. Another glass slide was kept on this microcapsule-hardener mixture and gently pressure was applied on the top slide. It was noted that epoxy from microcapsules flows out and gets set in presence of hardener. These two slides are found to stick to each other firmly (FIG. 1(a-d)). This experiment indicates that microcapsules get ruptured with pressure and epoxy resin from microcapsules comes out.

(19) The microcapsules prepared as exemplified herein are characterized by Scanning Electron Microphotographs (SEM) (FIG. 2(a-f)) and Optical images (FIG. 3(a-b)).

EXAMPLES

(20) Following examples are given by way of illustration therefore should not be construed to limit the scope of the invention.

Example 1

(21) Preparation of Microcapsules Containing Mixture of Water Soluble and Insoluble Epoxy Resin Using Polyurethane as Capsule Wall Material:

(22) In 250 ml beaker, 20 mg of Hypermer A70 and 0.5 gm of 1% dibutyltindilaurate (DBTDL) in paraffin oil were dissolved in 50 gm of paraffin oil. Beaker was assembled with overhead stirrer and reaction mixture was stirred at 500 rpm. Then 4.79 gm of IPDI was dissolved in 6 gm of epoxy resin mixture. This solution was added into the reaction mixture and stirred for 15 min to stabilize the emulsion. Then 1 gm of ethylene glycol and 0.2 gm of trimethylol propane in 3 gm paraffin oil was added in reaction mixture drop wise over the period of 14 minutes. Reaction mixture was then stirred for 30 minute at 40 C. and then 30 minute at 50 C. Thereafter temperature was raised to 60 C. and stirred for further 4 hours. Then the reaction temperature was brought to 35 C. and kept for overnight. After stirring for 23 hours, 90 ml pet ether was added and was stirred for 30 minutes. After the completion of reaction, mixture was centrifuged at 3000 rpm for 2 minutes and washed with pet ether.

(23) Finally microcapsules were dispersed in 50 ml pet ether and 1.2 gm of nano silica was added. This dispersion was then poured into Petri-dish and allowed to evaporate in air. Obtained microcapsules were dried in air for overnight (15 hr). The epoxy microcapsules have size range of 2-75 microns, of which majority of capsules were 10-25 microns. The Yield of the epoxy microcapsules obtained was 72%.

Example 2

(24) Preparation of Microcapsules Containing Water-Insoluble Epoxy Resin and Epoxy as Capsule Wall Material:

(25) In 250 ml beaker, 40 mg of Hypermer A70 was dissolved in 50 gm of paraffin oil. Beaker was assembled with overhead stirrer and reaction mixture was stirred at 500 rpm. Then 9.26 gm of water-insoluble epoxy resin (diglycidyl ether of bisphenol A) was added and stirred for 20 minute to stabilize the emulsion. Then 0.5 gm diethylene triamine (DETA) in 3 gm paraffin oil was added in reaction mixture drop wise over the period of 12 minutes. Reaction mixture was then stirred for 30 minute at 40 C. and then 30 minute at 50 C. Thereafter temperature was raised to 60 C. and stirred for further 4 hours. Then the reaction temperature was brought to 35 C. and kept for overnight. After stirring for 23 hours, 90 ml pet ether was added and was stirred for 30 minutes. After the completion of reaction, mixture was filtered by water suction pump and washed with pet ether.

(26) Finally microcapsules were dispersed in 50 ml pet ether and 0.8 gm of nano silica was added. This dispersion was then poured into Petri-dish and allowed to evaporate in air. Obtained microcapsules were dried in air for overnight (15 hr). The epoxy microcapsules have size range of 5-60 microns, of which majority of capsules were 10-30 microns. The Yield of the epoxy microcapsules obtained was 84%.

Example 3

(27) Preparation of Microcapsules Containing Water-Soluble Epoxy Resin and Epoxy as Capsule Wall Material:

(28) In 250 ml beaker, 40 mg of Hypermer A70 was dissolved in 50 gm of paraffin oil. Beaker was assembled with overhead stirrer and reaction mixture was stirred at 500 rpm. Then 4.52 gm of water-soluble epoxy (diglycidyl ether of butane diol) was added and stirred for 20 minute to stabilize the emulsion. Then 0.5 gm diethylene triamine (DETA) in 5 gm paraffin oil was added in reaction mixture drop wise over the period of 10 minutes. Reaction mixture was then stirred for 30 minute at 40 C. and then 30 minute at 50 C. Thereafter temperature was raised to 60 C. and stirred for further 4 hours. Then the reaction temperature was brought to 35 C. and kept for overnight. After stirring for 23 hours, 90 ml pet ether was added and was stirred for 30 minutes. After the completion of reaction, mixture was centrifuged at 3000 rpm for 2 minutes and washed with pet ether.

(29) Finally microcapsules were dispersed in 50 ml pet ether and 0.51 gm of nano silica was added. This dispersion was then poured into Petri-dish and allowed to evaporate in air. Obtained microcapsules were dried in air for overnight (15 hr). The epoxy microcapsules have size range of 2-50 microns, of which majority of capsules were 2-10 microns. The Yield of the epoxy microcapsules obtained was 87%.

Example 4

(30) Preparation of Microcapsules Containing Mixture of Water Soluble and Insoluble Epoxy Resin Using Polyurethane as Capsule Wall Material:

(31) In 250 ml beaker, 20 mg of Hypermer A70 and 0.5 gm of 1% DBTDL in paraffin oil were dissolved in 50 gm of paraffin oil. Beaker was assembled with overhead stirrer and reaction mixture was stirred at 500 rpm. Then 3.63 gm of hexamethylene1,6-diisocyanate (HMDI) was dissolved in 4.8 gm of epoxy resin mixture. This solution was added into the reaction mixture and stirred for 15 min to stabilize the emulsion. Then 1 gm of ethylene glycol and 0.2 gm of trimethylol propane in 3 gm paraffin oil was added in reaction mixture drop wise over the period of 15 minutes. Reaction mixture was then stirred for 30 minute at 40 C. and then 30 minute at 50 C. Thereafter temperature was raised to 60 C. and after 2 hours 20 mg of Hypermer A70 in 2 gm paraffin oil was added. Mixture was stirred for further 2 hours. Then the reaction temperature was brought to 35 C. and kept for overnight. After stirring for 23 hours, 90 ml pet ether was added and was stirred for 30 minutes. After the completion of reaction, mixture was centrifuged at 3000 rpm for 2 minutes and washed with pet ether.

(32) Finally microcapsules were dispersed in 50 ml pet ether and 0.5 gm of nano silica was added. This dispersion was then poured into Petri-dish and allowed to evaporate in air. Obtained microcapsules were dried in air for overnight (15 hr). The epoxy microcapsules have size range of 5-75 microns, of which majority of capsules were 25-50 microns. The Yield of the epoxy microcapsules obtained was 70%.

Example 5

(33) Preparation of Microcapsules Containing Mixture of Water Soluble and Insoluble Epoxy Resin Using Polyurethane as Capsule Wall Material:

(34) In 250 ml beaker, 20 mg of A70 Hypermer and 0.5 gm of 1% dibutyltin dilaurate (DBTDL) were dissolved in 50 gm of paraffin oil. The beaker was assembled with overhead stirrer and reaction mixture was stirred at 500 rpm. Then 2.32 gm of IPDI was dissolved in 3.52 gm of mixture of water soluble and insoluble epoxy resin. This solution was added into the reaction mixture and stirred for 15 min to stabilize the emulsion. Then 1 gm of ethyl hexyl glycol and 0.2 gm of trimethylol propane in 3 gm paraffin oil was added in reaction mixture drop wise over the period of 13 minutes (0.3-0.5 g/min). Reaction mixture was then stirred for 30 minutes at 40 C. and then 30 minutes at 50 C. Thereafter temperature was raised to 60 C. and stirred for further 4 hours. Then the reaction temperature was brought to 35 C. and kept for overnight. After the stirring of 22 hours, 90 ml pet ether was added and was stirred for 30 minutes. After the completion of reaction, mixture was centrifuged at 3500 rpm for 3 minutes and washed with pet ether.

(35) Finally microcapsule was dispersed in 50 ml pet ether and 0.7 gm of nano silica was added. This dispersion was then poured into Petri-dish and allowed to evaporate in air. Obtained microcapsules were dried in air for overnight (15 hr).

(36) The epoxy microcapsules have size range of 2-55 microns, of which majority of capsules were 10-15 microns. The Yield of the epoxy microcapsule obtained was 84%.

Example 6

(37) Preparation of Microcapsules Containing Mixture of Water Soluble and Insoluble Epoxy Resin Using Polyurethane as Capsule Wall Material:

(38) In 250 ml beaker, 20 mg of A70 Hypermer and 0.5 gm of 1% dibutyltin dilaurate (DBTDL) were dissolved in 50 gm of paraffin oil. The beaker was assembled with overhead stirrer and reaction mixture was stirred at 500 rpm. Then 1.81 gm of TDI was dissolved in 3.02 gm of mixture of water soluble and insoluble epoxy resin. This solution was added into the reaction mixture and stirred for 15 min to stabilize the emulsion. Then 1 gm of ethyl hexyl glycol and 0.2 gm of trimethylol propane in 3 gm paraffin oil was added drop wise in reaction mixture over the period of 15 minutes (0.28-0.5 g/min). Reaction mixture was then stirred for 30 minutes at 40 C. and then 30 minutes at 50 C. Thereafter temperature was raised to 60 C. and stirred for further 4 hours. Then the reaction temperature was brought to 35 C. followed by addition of 0.2 gm of fumed silica and kept for overnight. After the stirring of 22 hours 0.1 gm fumed silica added and stirring continued for further 1 hour, then 90 ml pet ether was added and stirred for next 30 minutes. After the completion of reaction, mixture was filtered and washed with pet ether.

(39) Finally microcapsule was dispersed in 50 ml pet ether and 0.07 gm of nano silica was added. This dispersion was then poured into Petri-dish and allowed to evaporate in air. Obtained microcapsules were dried in air for overnight (15 hr). The epoxy microcapsules have size range of 10-60 microns. The Yield of the epoxy microcapsule obtained was 79%.

Example 7

(40) Preparation of Microcapsules Containing Mixture of Water Soluble and Insoluble Epoxy Resin Using Polyurethane as Capsule Wall Material:

(41) In 250 ml beaker, 20 mg of A70 Hypermer and 0.5 gm of 1% dibutyltin dilaurate (DBTDL) were dissolved in 50 gm of paraffin oil. The beaker was assembled with overhead stirrer and reaction mixture was stirred at 500 rpm. Then 3.76 gm of TDI was dissolved in 4.96 gm of mixture of water soluble and insoluble epoxy resin. This solution was added into the reaction mixture and stirred for 20 min to stabilize the emulsion. Then 1 gm of ethylene glycol and 0.2 gm of trimethylol propane in 3 gm paraffin oil was added drop wise in reaction mixture over the period of 15 minutes (0.28-0.5 g/min). Reaction mixture was then stirred for 30 minutes at 40 C. and then 30 minutes at 50 C. Thereafter temperature was raised to 60 C. and stirred for further 4 hours. Then the reaction temperature was brought to 35 C. and kept for overnight followed by addition of 0.3 gm fumed silica. After the stirring of 22 hours 0.3 gm fumed silica added and stirred for further one hour, then 90 ml pet ether was added and was stirred for 30 minutes. After the completion of reaction, mixture was centrifuged at 4000 rpm for 5 minutes and washed with pet ether.

(42) Finally microcapsule was dispersed in 50 ml pet ether and 10% (w.r.t. theoretical yield) nano silica was added. This dispersion was then poured into Petri-dish and allowed to evaporate in air. Obtained microcapsules were dried in air for overnight (15 hr). The epoxy microcapsules have size range of 5-45 microns, of which majority of capsules were 10-30 microns. The Yield of the epoxy microcapsule obtained was 85%.

Example 8

(43) Preparation of Microcapsules Containing Mixture of Water Soluble and Insoluble Epoxy Resin Using Polyurethane as Capsule Wall Material:

(44) In 250 ml beaker, 15 mg of A70 Hypermer and 0.5 gm of 1% dibutyltin dilaurate (DBTDL) were dissolved in 50 gm of paraffin oil. The beaker was assembled with overhead stirrer and reaction mixture was stirred at 500 rpm. Then 2.6 gm HMDI was dissolved in 3.8 gm of mixture of water soluble and insoluble epoxy resin. This solution was added into the reaction mixture and stirred for 20 min to stabilize the emulsion. Then 1 gm of butane diol and 0.2 gm of trimethylol propane in 3 gm paraffin oil was added drop wise in reaction mixture over the period of 10 minutes (0.4-0.5 g/min). Reaction mixture was then stirred for 30 minutes at 40 C. and then 30 minutes at 50 C. Thereafter temperature was raised to 60 C. and stirred for further 4 hours. Then the reaction temperature was brought to 35 C. and kept for overnight. After the stirring of 23 hours, 90 ml pet ether was added and was stirred for 30 minutes. After the completion of reaction, mixture was filtered out and washed with pet ether.

(45) Finally microcapsule was dispersed in 30 ml pet ether and 0.76 gm of nano silica was added. This dispersion was then poured into Petri-dish and allowed to evaporate in air. Obtained microcapsules were dried in air for overnight (15 hr). The epoxy microcapsules have size range of 2-70 microns, of which majority of capsules were 15-60 microns. The Yield of the epoxy microcapsule obtained was 83%.

Example 9

(46) Preparation of Microcapsules Containing Water Soluble Epoxy Resin Using Epoxy as Capsule Wall Material:

(47) In 250 ml beaker, 40 mg of A70 Hypermer was dissolved in 50 gm of paraffin oil. The beaker was assembled with overhead stirrer and reaction mixture was stirred at 500 rpm. Then 6.94 gm water soluble epoxy was added and stirred for 10 minute to stabilize the emulsion. Then 0.5 gm of EDA and 0.1 gm triethylene tetraamine (TETA) as crosslinker (20% w.r.t EDA) was dissolved in 3 gm of paraffin oil. This solution was added into the reaction mixture drop wise over the period of 12 minutes (0.35-0.5 g/min). Reaction mixture was then stirred for 30 minutes at 40 C. and then 30 minutes at 50 C. Thereafter temperature was raised to 60 C. and stirred for further 4 hours. Then the reaction temperature was brought to 35 C. and kept for overnight (15 hr). After the stirring of 22 hours, 90 ml pet ether was added and stirred for 30 minutes. After the completion of reaction, mixture was filtered out washed with pet ether.

(48) Finally microcapsule was dispersed in pet ether and 0.76 gm of nano silica was added. This dispersion was then poured into Petri-dish and allowed to evaporate in air. Obtained microcapsules were dried in air for overnight (15 hr). The epoxy microcapsules have size range of 1-50 microns, of which majority of capsules were 5-15 microns. The Yield of the epoxy microcapsule obtained was 80%.

Example 10

(49) Preparation of Microcapsules Containing Water Insoluble Epoxy Resin and Epoxy as Capsule Wall Material:

(50) In 250 ml beaker, 40 mg of A70 Hypermer was dissolved in 50 gm of paraffin oil. Beaker was assembled with overhead stirrer and reaction mixture was stirred at 500 rpm. Then 8.18 gm of water insoluble epoxy was added and stirred for 20 minute to stabilize the emulsion. Then 0.5 gm triethylene tetraamine (TETA) dissolved in 3 gm paraffin oil and added drop wise in reaction mixture over the period of 5 minutes (0.7-0.9 g/min). Reaction mixture was then stirred for 30 minutes at 40 C. and then 30 minutes at 50 C. Thereafter temperature was raised to 60 C. and stirred for further 4 hours. Then the reaction temperature was brought to 35 C. and kept for overnight. After the stirring of 22 hours, 90 ml pet ether was added and stirred for 30 minutes. After the completion of reaction, mixture was centrifuged for 2 minutes and washed with pet ether. Obtained microcapsules were dried in air for overnight (15 hr). The epoxy microcapsules have size range of 2-100 microns, of which majority of capsules were 2-50 microns. The Yield of the epoxy microcapsules obtained was 92%.

Example 11

(51) Preparation of Microcapsules Containing Water Insoluble Epoxy Resin Using Polyurethane as Capsule Wall Material:

(52) In 250 ml beaker, 10 mg of A70 Hypermer and 0.5 gm of 1% dibutyltin dilaurate (DBTDL) were dissolved in 50 gm of paraffin oil. The beaker was assembled with overhead stirrer and reaction mixture was stirred at 500 rpm. Then 2.6 gm HMDI was dissolved in 3.8 gm of water insoluble epoxy. This solution was added into the reaction mixture and stirred for 15 min to stabilize the emulsion. Then 1 gm of butane diol and 0.2 gm of trimethylol propane (as a crosslinker) dissolved in 3 gm paraffin oil and added drop wise in reaction mixture over the period of 14 minutes (0.28-0.4 g/min). Reaction mixture was then stirred for 30 minutes at 40 C. and then 30 minutes at 50 C. Thereafter temperature was raised to 60 C. and stirred for further 4 hours. Then the reaction temperature was brought to 35 C. and kept for overnight. After the stirring of 23 hours, 90 ml pet ether was added and stirred for 30 minutes. After the completion of reaction, mixture was filtered out and washed with pet ether.

(53) Finally microcapsule was dispersed in 30 ml pet ether and 0.38 gm of nano silica was added. This dispersion was then poured into Petri-dish and allowed to evaporate in air. Obtained microcapsules were dried in air for overnight (15 hr). The epoxy microcapsules have size range of 2-75 microns, of which majority of capsules were 10-25 microns. The Yield of the epoxy microcapsule obtained was 87%.

Example 12

(54) Preparation of Microcapsules Containing Water Soluble Epoxy Resin Using Polyurethane as Capsule Wall Material:

(55) In 250 ml beaker, 20 mg of A70 Hypermer and 0.5 gm of 1% dibutyltin dilaurate (DBTDL) were dissolved in 50 gm of paraffin oil. The beaker was assembled with overhead stirrer and reaction mixture was stirred at 500 rpm. Then 2.6 gm HMDI was dissolved in 3.8 gm of water soluble epoxy. This solution was added into the reaction mixture and stirred for 20 min to stabilize the emulsion. Then 1 gm of butane diol and 0.2 gm of trimethylol propane (as a crosslinker) dissolved in 3 gm paraffin oil then added drop wise in reaction mixture over the period of 10 minutes (0.4-0.6 g/min). Reaction mixture was then stirred for 30 minutes at 40 C. and then 30 minutes at 50 C. Thereafter temperature was raised to 60 C. and stirred for further 4 hours. Then the reaction temperature was brought to 35 C. and kept for overnight. After the stirring of 23 hours 0.3 gm fumed silica was added and stirred for 1 hour, after that 90 ml pet ether was added and stirred for 30 minutes. After the completion of reaction, mixture was filtered out and microcapsules were washed with pet ether.

(56) Finally microcapsule was dispersed in 40 ml pet ether and 0.3 gm of fumed silica was added. This dispersion was then poured into Petri-dish and allowed to evaporate in air. Obtained microcapsules were dried in air for overnight (15 hr). The epoxy microcapsules have size range of 5-40 microns, of which majority of capsules were 15-25 microns. The Yield of the epoxy microcapsule obtained was 74%.

Example 13

(57) Preparation of Microcapsules Containing Mixture of Water Soluble and Insoluble Epoxy Resin Using Polyurethane as Capsule Wall Material:

(58) In 250 ml beaker, 20 mg of A70 Hypermer and 0.5 gm of 1% dibutyltin dilaurate (DBTDL) were dissolved in 50 gm of paraffin oil. The beaker was assembled with overhead stirrer and reaction mixture was stirred at 500 rpm. Then 3.48 gm of IPDI was dissolved in 4.68 gm of mixture water soluble and insoluble epoxy resin. This solution was added into the reaction mixture and stirred for 20 min to stabilize the emulsion. Then 1 gm of butane diol and 0.2 gm of trimethylol propane dissolved in 3 gm paraffin oil was added drop wise in reaction mixture over the period of 13 minutes (0.28-0.5 g/min). Reaction mixture was then stirred for 30 minutes at 40 C. and then 30 minutes at 50 C. Thereafter temperature was raised to 60 C. and stirred for further 4 hours. Then the reaction temperature was brought to 35 C. and kept for overnight. After the stirring of 23 hours 90 ml pet ether was added and stirred for 20 minutes. After the completion of reaction, mixture was centrifuged at 3000 rpm four times by 3 minutes interval and washed with pet ether.

(59) Finally microcapsule was dispersed in 60 ml pet ether and 0.9 gm nano silica was added. This dispersion was then poured into Petri-dish and allowed to evaporate in air. Obtained microcapsules were dried in air for overnight (15 hr). The epoxy microcapsules have size range of 5-75 micron of which majority of capsules were 10-20 microns. The Yield of the epoxy microcapsule obtained was 67%.

Example 14

(60) Characterization of Microcapsules (Rupture of Microcapsules with Pressure)

(61) To check if microcapsules containing epoxy resin break with pressure following experiment was carried out. Few mg of microcapsules from Example 1 containing mixture of water insoluble and soluble epoxy resin were taken on microscope glass slide along with few mg of hardener. Another glass slide was kept on this microcapsule-hardener mixture and gently pressure was applied on the top slide. It was noted that epoxy from microcapsules flows out and gets set in presence of hardener. These two slides were found to stick to each other firmly. This experiment indicates that microcapsules get ruptured with pressure and epoxy resin from microcapsules comes out.

(62) The microcapsules prepared as exemplified herein were characterized by Scanning Electron Microphotographs (SEM), refer FIG. 2 and Optical images, refer FIG. 3.

ADVANTAGES OF THE INVENTION

(63) Simple process of preparation The self-healing microcapsules of epoxy resin when embedded in composite structures releases the polymer forming material when crack is developed and that can seal the cracks instantaneously. The process described can produce microcapsules containing not only water-insoluble epoxy resin but water-soluble epoxy resin too.