CA2059851A1 - In-situ polymerization process for producing epoxy microcapsules - Google Patents
In-situ polymerization process for producing epoxy microcapsulesInfo
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- CA2059851A1 CA2059851A1 CA 2059851 CA2059851A CA2059851A1 CA 2059851 A1 CA2059851 A1 CA 2059851A1 CA 2059851 CA2059851 CA 2059851 CA 2059851 A CA2059851 A CA 2059851A CA 2059851 A1 CA2059851 A1 CA 2059851A1
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- bisphenol
- epoxy
- epoxy resin
- glycidyl ether
- liquid
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Abstract
ABSTRACT OF THE DISCLOSURE
A process for producing microcapsules by contacting an epoxy resin with a ketimine in the presence of water. The ketimine and epoxy resin are provided in a stable dispersion of droplets of a first liquid in an aqueous continuous phase of a second liquid.
The ketimine is hydrolyzed at the surface of the droplets to release a reactive amine. The reactive amine contacts the epoxy resin to form polymeric capsule walls of epoxy at the interface between the two phases. The resultant microcapsules are suitable for use in carbonless copying systems.
A process for producing microcapsules by contacting an epoxy resin with a ketimine in the presence of water. The ketimine and epoxy resin are provided in a stable dispersion of droplets of a first liquid in an aqueous continuous phase of a second liquid.
The ketimine is hydrolyzed at the surface of the droplets to release a reactive amine. The reactive amine contacts the epoxy resin to form polymeric capsule walls of epoxy at the interface between the two phases. The resultant microcapsules are suitable for use in carbonless copying systems.
Description
20~98~1 IN-SITU POLYMERIZATION PROCESS FOR PRODUCING
~PO~Y MICROCAPSUL~S
Backqround of tho Inventlon 1 Pield of th~ Invention The present invention relates to microcapsules and methods of microencapsulating a core of fill material. The resulting microcapeules are adaptable to a variety of applications, but are particularly for u~e in carbonle s copying systemsO
Descri~tion of the Prior Art Microcapsulec generally comprise a core of fill material ~urrounded by a wall or shell of polymeric material. The fill material may be either gaseous, liquid, or ~olid and may be composed of a ~ingle substance, a 301ution, a ~u~pen~ion or a mixture of substance~. The wall ~urrounding the core of fill material acts to i301ate the fill material from the external environment. When :Lt i9 desirable to release the fill material, tho capsule wall may be ruptured to thereby introduce the fill material into its ~urrounding3. Generally, microcap3ules comprise separate and discrete cap4ules, thuR the fill material i~
enveloped within the generally continuous polymeric walls of a microcap~ule.
~, ~
20~9~51 1 A process for the production of microcapsules using coacervation is disclosed in U.S. Patent No. 4,228,031 to Iwasaki et al. A process is described for making impermeable microcapsules comprising preparing an aqueous dispersion of microcapsules each having a capsule wall. The capsule wall is a coacervate of a cationic polyamine-epoxy resin/anionic colloid.
An electrolyte is added to dehydrate the wall. The coacervate wall contain~ as high a~ 80% water. Preferably, dehydration of the microcapsules is carried out to such an extent that each of the microcapsules is deformed into a hollow ball form.
Coacervation has a number o f disadvantages. As the properties of natural colloids are not standardized, coacervation conditions such as temperature and pH-value have to ba continually ad~usted. Accordingly, the process cannot be carried out lS continuously. A1YO, as a result of agglomeration, microcapsules with an undesirably wide particle size di~tribution are obtained.
This technology doe~ not relate, except by way of background, to in- itu formation of polymeric microcap~ule wall~ as disclosed in the instant invention.
There are ~everal known proce~se~ for the production of microcapsules by ln~erfacial polymerization. ~enerallyl these procecses use a system of two phases. One phase is a discontinuous phaso which i~ used to form the coro of the microcap4ules. This ph~se contains, in solution, one or two substances capable of wall formation, which are insoluble in the continuous phase. The continuous phase contain~ the other substance, which is nec2ssary ~o react and form polymaric walls.
20~98~
1 Generally, the second reactant should have some solubility (i.e., partition coefficient) in the discontinuous phase, in order to effectively migrate from the continuous phase to react at the interface. A polymerization reaction takes place at the interface between the two phases resulting in a shell surrounding the core material.
One disadvantage common to these processes lies in the fact that, after the formation of a first extremely thin capsule membrane, mutual contact between the wall-forming compounds may be made difficult or even impossible. The result of this i5 that both the core material and also the aqueous phase remain contaminatad by unreacted material, thus making it more difficult to ad~ust the thickness of the capsule wall.
U.5. Patent No. 4,459,509 to Chao describes a process for forming microcapsules using two organic-in-aqueous emulsions, each containing at least one oil soluble reactive compound that will react to form polymeric microcapsule walls. Microencapsulation is obtained by mixing the two organic-in-aqueous emulsions for a time and temperature sufficient to permit the emulsified organic droplets of each emulsion to collide with one another. Collision of two or more emulsions droplets causes the emulsified droplets to exchange ~t le~st a portion of their contents.
U.S. Patent No. 4,625,471 to Chao describes a proceqs for in-situ polymerization of microcapsule walls by forming 8 solution containing a polyfunc~ional amLnel an epoxy resin selected from the group of methylolated bisphenol A based epoxy resins, and an organic ~olven~. ~he resulting solution i8 then emul~ified or 20~9~
1 dispersed to form droplets within a substantially continuous aqueous phase. The amine compound polymerizes the epoxy resin and the polymeric reaction product migrates outward to the interface of the organic droplet and the substantially aqueous phase. This polymerization and migration eventually r0sults in the formation of a microcapsule wall at the interfacs.
U.S. Patent 3,432,327 to Ran et al. describes a process for forming capsules by int rfacial polymerization of a~ epoxy resin and an amine in hydrophilic and hydrophobic liquid~.
U.S. Patent ~o. 4,120,518 to Baatz et al. discloses a process for forming microcapsules containing a solution of color formers and having polyurea shells. The process de~cribe~ an oil-in-water emulQion with a polycarbodimide incorporated in the oil phase, which will react with an amine contained within the aqueous phase to form microcapsuleq at the phase interface.
U.S. Patent No. 3,981,821 to Kiritani et al. describes a proce~s for forming microcapsules by emulsifying a hydrophobic liquid, to be encapsulated as a dispersed phase, in a hydrophilic liquid immiscible therewith as a continuous phase. At least one cap~ule wall-forming ~ubstance present in the hydrophilic liquid continuous phase is then polymerized and the resultlng polymer is deposited around the hydrophobic liquid droplets from the outside.
A ~ubstance in the continuous phase~ that ha~ reactivity with at least one of the wall-forming sub4tance~ promote~ the deposition of the polymer, resulting in the continuous pha~e being present in the droplets of the hydrophobic liquid prior to the step of emulsifyiny the hydrophobic liquid.
20~98~
1 U.S. Patent 4,317,743 to Chang disclose~ a process for forming microcapsules by forming an oil-in-water emulsion. ~he oil phase comprises materials to be encapsulated and isocyanatoamidine product as the wall-forming material in a hydrophobic liquid. The aqueous phase contains a water-soluble emulsifier which acts solely as the protective colloid. The isocyanatoamidine product is then hydrolyzed at the interface of each oil droplet into a strong solid capsule wall which is insoluble in either the oil or water.
10- U.S. Patent No. 4,138,362 to Vassiliades et al. describes a process for forming pressure-rupturable, oil-containing microcapsule~ by admixing a water-immi~cible, oily material containing an oil soluble, non-polymeric polyfunctional isocyanate cross-linking agent, and an aqueous solution of a polymeric emulsifying agent in the form of ~ water soluble polymer containing recurring -NH2 or =NH groups or a water soluble natural gum containing recurring hydroxy groups. An oil-in^water emulsion $s formed and a solid cspsule wall i~ formed by the croYs-linking of the emulsifying agent by the isocyanate.
There are several disadvantages associatad with the above proces~es of maklng microcapsules, due to the rapid reaction of the two wall-forming materialR during the emulsification step.
The size and shape of the microcapsule3 varies over a wide range, making control of the microcapsule size and size distribution difficult if not impo3sible.
20598~1 1 U.S. Patent No. 4,356,108 to Schwab et al. describes a process for forming microcapsules by interfacial condensation of a polyfunctional amine and a polyfunctional wall forming material reactable with the amine. The process comprises emulsifying a mixture of a hydrophobic pha-~e which includes an oil, a chromogenic material and an oil soluble polyfunctional wall-forming material, and a hydrophilic phase, which includes water, a water soluble emulsifying agent and a water ~oluble salt of the desired polyfunctional amine. The amine salt may be formed in-situ in the hydrophilic phase before the emulsification step.
After emul~ification, ~ufficient base is added to the emulsion to convert the polyfunctional amine salt to a polyfunctional amine and to neutralize acid formed during ~ub~equent condensation reactions, thuY initiating the re~ction of the polyfunctional amine with the oil soluble polyfunc~ional wall forming material and thus forming microcapsule walls around the dropletc of the hydrophobic phase. The maskad amine used in Schwab~ patent, which disclose~ an interfacial proce3g~ i8 a water soluble salt.
It cannot be incorpor~tsd into an oil core pha~e for use in in-situ polymerization procQs~e~.
U.S. Patent No. 4,428,983 to Nehen et ~1. de3cribes a process for forming microcap~ulos by in-~itu polymeriz~tion in which a stabilized dispersion of droplets of a fir~t liquid to be encapsulated or a stabilized dispersion of solid particles to be encapsulated iQ formed in a continuous pha~e of a second liquid.
One of the two capsule wall-forming reaction components is present in free form and contains at lea~t two isocyanate group4 while the 20~9~1 1 other of the two cap3ule wall-forming reaction components is present in reversibly blocked form and contains at least two reversibly blocked functional groups. The functional groups are deblocked by water and contain at least two NH groups or one NH
S qroup and one OH group. Both reaction components are present in the first or second liquid without reacting with one another. The reaction component which is present in reversibly blocked form is deblocked by means of water present in the first or second liquid and then reacts with the reaction component present in free form 1~ to form ~ polymeric capsule wall. The droplets of the first liquid or the solid particles are thus encapsulated in small capsules consisting of polymeric material.
Summary of tha In~ention It is an ob~ect of the present invent~on to provide a process for the formation of epoxy microcapsules having uniform wall thickneqs and capsule 8ize distribution. In-~itu polymerization of the microcapsules by the process of the present invontion results in microc~p~uleR highly suitable for usn in carbonless copying sy-~tem~.
In the proceE~s according to the present invention, microcap~ules sre produced by in-situ polymerization. Two wall-forming components, ~n apoxy and a ~etimine, ara provided within a first liquid. The fir~t liquid preferably contain~ a colorless dye precur~or or precursor mixture in an organic carrier solvent.
A stable disper~ion of droplets of the fir-qt liquid iR formed in a continuous phase of a second liquid. An oil/water emul~ion is ~Q~8~1 1 formed in the presence of an emulsifier, of which water is the main ingredient. Droplet sizes are determined by the emulsifier type and its concentration, emulsifLcation speed, time and temperature. The ketimine, which is incorporated together with an epoxy r~sin in the oil core discentinuouR phase, is hydrolyzed at the surface of the droplets by contact with the aqueous continuous phase to release a reactive amine. The released reactive amine then react~ with the epoxy resin to form polymeric capsule walls at the interface between the droplets of the fixst liquid and the aqueou~ continuous pha~e. The droplet-~ of the firqt liquid are encapsulated in capsules of epoxy.
Additional ob~ects and advantages of the invention will become apparent in the de~cription which follow~.
Brief D~scri~tion of the Drawinq~
Figura l i a scann~ng electron miCroQCOp~ photograph of a microcapsule di~persion of Versamine K-13, Araldite 6060 and KMC
oil at magnific~tions of 200X and 1000X.
Figure 2 i~ a scanning electron microscope photograph of a microcapsule dispersion of Versamine X-ll and Araldite 3337 at magnification~ of 200X and 1000X.
Figure 3 19 ~I scannlng electron microscope photograph of d microcapsule dlspersion of Versamine* K-ll and Araldite*6060 at magnifications of 200X and l000X.
Figure 4 i~ a scanning electron microscope photograph of a microcap~ule diqpersion of Ver~amine*X-ll and Araldite*3336 at magnifications of 200X and 1000X.
Trade-mark ~0~9~1 1 Figure S is a scanning electron microscope photograph of a microcapsule dispersion of Versamine K-12, Araldite 3337 and ~C/
Ucane at maqnifications of 200X and lOOOX.
Figure 6 is a scanning electron microscope photograph of a microcapsule dispersion of Versamine K-13, Araldite 3337 and ~UC/
Ucane.
Detailed DeseriPtion of the Preferred Embodiments The present invention relates to the microencapsulation of a core material in an epoxy microcapsule wall. The process employs two phases, a discontinuous phase tha~ forms the core materials to be encapsulated and a continuous pha~e. Within the core material phase i~ contained two wall-forming components, an epoxy resin and a ketimine. Upon hydrolysis of the ketimine, an amine is formed which is reactive with the epoxy resin.
Epoxy resins which are suitable for use in accordance with the present invention are the aromatic resins that contain multifunctional epoxide group~. For example, sisphenol A and Bisphenol F ba~ed glycidyl ethers, phenol and cre~ol based novolac re~ins, 1,1,2,2-(p-hydroxyphenol) ethane based glycidyl ether, ~-glycidyloxy-N,N-di-glycidyl aniline, methylolated bisphenol A
based re~in~, methylenedianiline based resin~, etc., are all useful in this invention. Preferably, bisphenol A and bisphenol F epoxy resinY are used.
_ g _ ~59~1 1 The bi~phenol A recin~ suitable for use in the instan invention preferably have an equivalent weight or WPE (weight pe_ epoxy) in the range of 175 to 500. Examples of suitable bisphenol A resins include Araldite 6005, 6010, 6020 and 6060, all from Ciba Geigy.
The bisphenol F resins suitable for use in the instant invention preferably have an equivalent weight or WPE in the range of 150-300. Examples of suitable bisphenol F resins include Araldite 281, 306, 3336 and 3337, all from Ciba Geigy.
XetimineQ ara amine-ketone adducts which are unreactive with epoxy resin. Upon release of amine through hydrolysis with water, the compound becomes reactive with epoxy resin. Ketimines which are 3uitable for use in accordance with the present invention correspond to the general formula:
H2NRNH2 + R'COR" -> R'R"C=NRN-CR'R"
wherein R iQ 2 lower alkyl radical, ~uch as methyl, ethyl, propyl, isopropyl, i~obutyl, ètc.
Preferably, ketimines of the following formulas are used.
R R
C = N - (CH2)2 - N ~ C (II) R H R
C a N - (CH2)2 - N ~ (CH2)2 ~ (III) 20~851 C = N - (CH2)2 - I ~ (CH2)2 ~ (IV) CH3 ~ CH2 c~3 CH - OH
o (~ .
wherein R is an isobutyl radical.
Other aliphatic amineR, such as hexamethylenediamine, dipropylenetriamine and triethylenetetra~ine c~n be reacted with methyl isobutyl ketone (MIBK) to form other ketimines which are suitable for use in the present invention. Examples of suitable ketimines are Versamine K-ll, ~-12 and R-13, all from Henkel Chemicals. Versamine K-11, K-12 and X-13 correspond to Formulas II, III and IV, respectively.
The rate of the reaction can be increased by the addition of a small amount of accelerator~ Acc~lerators which are suitable for u~e in ths pre~ent in~entlon include accelerator 399 (from Texaco chemicals)~ DMP-10 and DMP-30 (both from Rohm ~ Haas).
The discontiriuous phase contains at least one organic carrier solvent which contains at least one substance to be encapsula~ed, for example, a colorless dye or a colorles~ dye precur-~or. The organic carrier sol~ent should be capable of dissolving or ~uspending the dye precursor. Typical orsanic carrier solvents include alkyl naphthalene~, diarylalkane3, alkylated biphenyls, terphenyl~, linear alkyl benzenes and phthalate ester~.
~2.0~51 1 In COnnQction with carbonless copy systems, the fill material to be encapsulated within the inventive microcapsules will usually be a colorless dye precursor such as crystal violet lactone (CVL) benzoylleucomethylene blue (~LMB), rhodamine lactam, p-S toluene~ulfinatQ of Michler's hydrol (PTSMH), or any of the various chromogenic compounds that ara capable of changing from a colorless to a colored form on contact with reactive substances, such as phenolic resins or reactive clays.
Generally, once the ~ubstance to be encapsulated (i.e. the colorless dye precur~or or precurRor mixture) i~ di~solved in a carrier organic solvent, the solution can be mixed with the epoxy res$n and the ketimine compound. To thls 001ution can be added an emul~ification aqent which aids in the formation of a oil-in-water emulsion. Typical emul~ification agents include partially hydrolyzed polyvinyl acetate, such a~ Vinol 523 and 540 from Air Products and Chemlcals; sodium naphthalene sulfonate/formaldehyde condensate, such as Tamol~ L from Rohm & Haas Chemicals; gelatins, starch and cellulose derivatives such as carboxylated starch or celluloce, hydrcxyethyl cellulose, polyacrylamide, polystyrQnesulfon~te, etc. Suitable emul~ification agents are tho~e Rurface active chemical~ which contain both hydrophilic and hydrophobic groups in the same molecules. In an oil/water emulsion, thes~ molQcules adsorb at the oil-wat~r interface, prevent$ng the oll droplet~ from collap~ing into each other.
Particle size of the o$1 droplet~ can be ad~usted by emul~ification agent concentration, ~peed, temperature and time of agitation. Particle size~ in the range of 1-10 microns are most *
Trade-mark 20~98~1 1 suitable for çarbonless paper application~. Capsules useful for other applications may need ad~ustment of their sizes. During emulsification, the oil droplets are in a state of intermediate contact with water molecules. Consequently, a reactive amine is released due to the hydrolysis of the ketimine. The newly released reactive amino compound reacts with a nearby epoxy resin molecule in-situ. Upon completion of the reaction, microcapsules having epoxy walls and an encapsulated core material in an organic carrier solvent are formed. Warming of the emulsion slurry to about 60 to 95C, preferably to about 70-85C, accelerates the curing rate.
The present invention and some of its advantages are further illustrated, but not limited, by the following examples.
63 parts of a 6~ colorless dye in KMC oil were mixed with 8.11 parts of Araldite 6060, 0.97 parts of Versamine K-ll and 0.2~
parts of Accelerator 399. The mixture was emulsified in 130 parts of a 3% aqueou~ Tamol L/Vinol 523 (95:5) ~olution. The slurry was heated to 75C for four hours. Under 3canning electron microscope, spherical microcapsules were obtained. Average particle size was about 5 microns. The capsule slurry was coated as a CB sheet. When it wa~ written against a phenolic resin coated receiving sheet, a clear black image was obtzined.
20598~1 1 EXAMPL~ 2 63 parts of a 6~ colorless dye in KMC oil were mixed with 6.87 parts of Araldite 3336, 2.20 parts of Versamine ~-11 and 0.20 parts of Accelerator 399. The mixture was emulsified in 130 parts of a 3~ aqueous Tamol LtVinol 523 (95:5) solution. The slurry was heated to 75C for four hour~. Under scanning electron microscope, spherical microcapsules were obtained. Average particle size was about 6 microns. The capsule slurry was coated as a C3 sheet. When it was written against a phenolic resin coated receiving sheet, a clear black image was obtained.
, .
63 parts of a 63 colorless dye in KMC oil were mixed with 7.0 parts of Araldite 3337, 2.07 parts of Versamine K-ll and 0.20 parts of Accelerator 399. The mixture was emulsified in 130 parts of a 3~ aqueous Tamol L/Vinol 523 (95:5) olution. The slurry was heated to 75C for four hours. Under scanning electron microscope, spherical microcapqules were obtained. Average particle size was about 4 microns. The capsule ~lurry was coated a9 a CL sheet. When it was written against a phenolic resin coated receiving shcet, a clear black image was obtained.
E~AMPL~ 4 * *
63 parts of a 6~ colorless dye in Sure~ol 330/Ucane 11 (50s50) ~olution were mixed wlth 6.98 parts of Araldite 6010, 2.09 parts of Versamine X-12 and 0.21 part~ of Accelerator 399. The mixture was emulsified in 130 parts of a 3~ aqueous Tamol L/Vi,sol Trade~mark 2~5~8~
1 523 (95:5) solution. The slurry was heated to 75C for feur hours. Under scanning electron microscope, spherical microcapsules were obtained. Average particie size was about 5 microns. The capsule slurry was overcoated onto a phenolic resin coated receiving sheet. Under writing pressure, a clear black image was obtained.
63 parts of a 6% colorless dye in Suresol 330/Ucane 11 (50:s0) solution were mixed with 8.1 parts of Araldite 6060, 0.98 parts of versamine ~-12 and 0.1 parts of Accelerator 399. The mixture was emul~ified in 130 parts of a 3~ aqueou-~ Tamol L/Vinol 523 (95:5) solution. The slurry was heated to 75C for four hours. Under scanning electron microscope, spherical microcapsules were obtained. Average particle size was about ~.5 microns. The cap~ule slurry was overcoated onto a phenolic resi~
coated receiving sheet. Under writing pressure, a clear black image was obtained.
63 parts of a 6% colorless dye in Suresol 330/Ucane 11 (50:50) ~olution were mixed with 6.86 parts of Araldite 281, 2.22 parts of VerYamine X-12 and 0.22 parts of Accelerator 399. The m$xture waq emulsified in 130 parts of a 3% aqueous Tamol L/Vi-.^l 523 (95:5) solution. The ~lurry wa~ heated to 75C for four hours. Under scanning electron microscope, spherical microcapsules were obtained. Average particle size was about ~5~5~
1 microns. The capsule slurry was overcoated onto a phenoli~ -esin coated receiving sheet. Under writing pressure, a clear bla-k image was obtained.
~A~PLE 7 - 63 parts of a 6% colorless dye in KMC/Ucane 11 (50:50) solution were mixed with 6.86 parts of Araldite 3336, 2.24 parts of Versamine K-12 and 0.22 parts of Accelerator 399. The mix.ure was emulsified in 130 parts of a 3% aqueous Tamol L/Vinol 523 10- (95:5) solution. The slurry was heated to 75C for four hours.
Under qc~nning electron microscope, Ypherical microcapsuleq were obtained. Average particle size was about 4 micron~. The capsule slurry was overcoated onto a phenolic resin coated receiving sheet. Under writing pressure, a clear black image was obtained.
~XA~PLE 8 63 parts of a 6~ colorless dye in Suresol 330/Ucane 11 t50:50) solution were mixed wlth 6.47 parts of Araldite 6010, 2.'6 parts of Versamine X-13 and 0.2 parts of Accelerator 399. The mixture wa~ emulsified in 130 parts of a 3~ aqueou~ Tamol L/Vinol 523 t95:5) solution. The slurry was heated to 75C for four hours. Under scanninq electron microscope, spherical microcapsules were obtained. Average particle size was about ~.5 microns. The cap~ule slurry was overcoated onto a phenolic resln coated receiving sheet. Under writing pre~sure, a clear blac~
image was obtained.
2~8~
1 , EXAMPLE 9 63 parts of a 6~ colorless dye in Suresol 330/Ucane 11 (s0:50) solution were mixed with 6.26 parts of Araldite 281, 2.82 parts of versamine X-13 and 0.21 parts of Accelerator 399. The mixture was emulsified in 130 parts of a 3% aqueous Tamol L/Vinol 523 (95:5) solution. The slurry was heated to 75C for four hours. Under scanning electron microscope, spherical microcapsules were obtained. Average particle size was about 5 microns. The capsule slurry was overcoated onto a phenolic resin coated receiving sheet. Under writing pressure, a clear black image was obtained.
63 parts of a 6~ colorless dye in KMC/Ucane 11 (50:50) solution were mixed with 6.36 parts of Araldite 3337, 2.72 parts of versamine R-13 and 0.2 parts of Accelerator 39g. The mixture was emulsified in 130 parts of a 3~ aqueous Tamol L/Vinol 523 (95:5) qolution. The slurry was heated to 75C for four hours.
Under scanning electron microscope, spherlcal microcapsules were obtained. Average particle size was about 4 microns. The capsule slurry wa~ overcoated onto a phenolic resin coated receivinq sheet. Under writing pressure, a clear black image was obtained.
Although the pre~ent invention has been described in connection with the preferred embodiments, it is to be understood that modlficstion~ and variations may be resorted to without - 17 _ ~OS98~1 departing from the spirit and scope of the invention. Such modifications are considered to be within the purview and s~cpe o.
the inven~ion and the appended claims.
~PO~Y MICROCAPSUL~S
Backqround of tho Inventlon 1 Pield of th~ Invention The present invention relates to microcapsules and methods of microencapsulating a core of fill material. The resulting microcapeules are adaptable to a variety of applications, but are particularly for u~e in carbonle s copying systemsO
Descri~tion of the Prior Art Microcapsulec generally comprise a core of fill material ~urrounded by a wall or shell of polymeric material. The fill material may be either gaseous, liquid, or ~olid and may be composed of a ~ingle substance, a 301ution, a ~u~pen~ion or a mixture of substance~. The wall ~urrounding the core of fill material acts to i301ate the fill material from the external environment. When :Lt i9 desirable to release the fill material, tho capsule wall may be ruptured to thereby introduce the fill material into its ~urrounding3. Generally, microcap3ules comprise separate and discrete cap4ules, thuR the fill material i~
enveloped within the generally continuous polymeric walls of a microcap~ule.
~, ~
20~9~51 1 A process for the production of microcapsules using coacervation is disclosed in U.S. Patent No. 4,228,031 to Iwasaki et al. A process is described for making impermeable microcapsules comprising preparing an aqueous dispersion of microcapsules each having a capsule wall. The capsule wall is a coacervate of a cationic polyamine-epoxy resin/anionic colloid.
An electrolyte is added to dehydrate the wall. The coacervate wall contain~ as high a~ 80% water. Preferably, dehydration of the microcapsules is carried out to such an extent that each of the microcapsules is deformed into a hollow ball form.
Coacervation has a number o f disadvantages. As the properties of natural colloids are not standardized, coacervation conditions such as temperature and pH-value have to ba continually ad~usted. Accordingly, the process cannot be carried out lS continuously. A1YO, as a result of agglomeration, microcapsules with an undesirably wide particle size di~tribution are obtained.
This technology doe~ not relate, except by way of background, to in- itu formation of polymeric microcap~ule wall~ as disclosed in the instant invention.
There are ~everal known proce~se~ for the production of microcapsules by ln~erfacial polymerization. ~enerallyl these procecses use a system of two phases. One phase is a discontinuous phaso which i~ used to form the coro of the microcap4ules. This ph~se contains, in solution, one or two substances capable of wall formation, which are insoluble in the continuous phase. The continuous phase contain~ the other substance, which is nec2ssary ~o react and form polymaric walls.
20~98~
1 Generally, the second reactant should have some solubility (i.e., partition coefficient) in the discontinuous phase, in order to effectively migrate from the continuous phase to react at the interface. A polymerization reaction takes place at the interface between the two phases resulting in a shell surrounding the core material.
One disadvantage common to these processes lies in the fact that, after the formation of a first extremely thin capsule membrane, mutual contact between the wall-forming compounds may be made difficult or even impossible. The result of this i5 that both the core material and also the aqueous phase remain contaminatad by unreacted material, thus making it more difficult to ad~ust the thickness of the capsule wall.
U.5. Patent No. 4,459,509 to Chao describes a process for forming microcapsules using two organic-in-aqueous emulsions, each containing at least one oil soluble reactive compound that will react to form polymeric microcapsule walls. Microencapsulation is obtained by mixing the two organic-in-aqueous emulsions for a time and temperature sufficient to permit the emulsified organic droplets of each emulsion to collide with one another. Collision of two or more emulsions droplets causes the emulsified droplets to exchange ~t le~st a portion of their contents.
U.S. Patent No. 4,625,471 to Chao describes a proceqs for in-situ polymerization of microcapsule walls by forming 8 solution containing a polyfunc~ional amLnel an epoxy resin selected from the group of methylolated bisphenol A based epoxy resins, and an organic ~olven~. ~he resulting solution i8 then emul~ified or 20~9~
1 dispersed to form droplets within a substantially continuous aqueous phase. The amine compound polymerizes the epoxy resin and the polymeric reaction product migrates outward to the interface of the organic droplet and the substantially aqueous phase. This polymerization and migration eventually r0sults in the formation of a microcapsule wall at the interfacs.
U.S. Patent 3,432,327 to Ran et al. describes a process for forming capsules by int rfacial polymerization of a~ epoxy resin and an amine in hydrophilic and hydrophobic liquid~.
U.S. Patent ~o. 4,120,518 to Baatz et al. discloses a process for forming microcapsules containing a solution of color formers and having polyurea shells. The process de~cribe~ an oil-in-water emulQion with a polycarbodimide incorporated in the oil phase, which will react with an amine contained within the aqueous phase to form microcapsuleq at the phase interface.
U.S. Patent No. 3,981,821 to Kiritani et al. describes a proce~s for forming microcapsules by emulsifying a hydrophobic liquid, to be encapsulated as a dispersed phase, in a hydrophilic liquid immiscible therewith as a continuous phase. At least one cap~ule wall-forming ~ubstance present in the hydrophilic liquid continuous phase is then polymerized and the resultlng polymer is deposited around the hydrophobic liquid droplets from the outside.
A ~ubstance in the continuous phase~ that ha~ reactivity with at least one of the wall-forming sub4tance~ promote~ the deposition of the polymer, resulting in the continuous pha~e being present in the droplets of the hydrophobic liquid prior to the step of emulsifyiny the hydrophobic liquid.
20~98~
1 U.S. Patent 4,317,743 to Chang disclose~ a process for forming microcapsules by forming an oil-in-water emulsion. ~he oil phase comprises materials to be encapsulated and isocyanatoamidine product as the wall-forming material in a hydrophobic liquid. The aqueous phase contains a water-soluble emulsifier which acts solely as the protective colloid. The isocyanatoamidine product is then hydrolyzed at the interface of each oil droplet into a strong solid capsule wall which is insoluble in either the oil or water.
10- U.S. Patent No. 4,138,362 to Vassiliades et al. describes a process for forming pressure-rupturable, oil-containing microcapsule~ by admixing a water-immi~cible, oily material containing an oil soluble, non-polymeric polyfunctional isocyanate cross-linking agent, and an aqueous solution of a polymeric emulsifying agent in the form of ~ water soluble polymer containing recurring -NH2 or =NH groups or a water soluble natural gum containing recurring hydroxy groups. An oil-in^water emulsion $s formed and a solid cspsule wall i~ formed by the croYs-linking of the emulsifying agent by the isocyanate.
There are several disadvantages associatad with the above proces~es of maklng microcapsules, due to the rapid reaction of the two wall-forming materialR during the emulsification step.
The size and shape of the microcapsule3 varies over a wide range, making control of the microcapsule size and size distribution difficult if not impo3sible.
20598~1 1 U.S. Patent No. 4,356,108 to Schwab et al. describes a process for forming microcapsules by interfacial condensation of a polyfunctional amine and a polyfunctional wall forming material reactable with the amine. The process comprises emulsifying a mixture of a hydrophobic pha-~e which includes an oil, a chromogenic material and an oil soluble polyfunctional wall-forming material, and a hydrophilic phase, which includes water, a water soluble emulsifying agent and a water ~oluble salt of the desired polyfunctional amine. The amine salt may be formed in-situ in the hydrophilic phase before the emulsification step.
After emul~ification, ~ufficient base is added to the emulsion to convert the polyfunctional amine salt to a polyfunctional amine and to neutralize acid formed during ~ub~equent condensation reactions, thuY initiating the re~ction of the polyfunctional amine with the oil soluble polyfunc~ional wall forming material and thus forming microcapsule walls around the dropletc of the hydrophobic phase. The maskad amine used in Schwab~ patent, which disclose~ an interfacial proce3g~ i8 a water soluble salt.
It cannot be incorpor~tsd into an oil core pha~e for use in in-situ polymerization procQs~e~.
U.S. Patent No. 4,428,983 to Nehen et ~1. de3cribes a process for forming microcap~ulos by in-~itu polymeriz~tion in which a stabilized dispersion of droplets of a fir~t liquid to be encapsulated or a stabilized dispersion of solid particles to be encapsulated iQ formed in a continuous pha~e of a second liquid.
One of the two capsule wall-forming reaction components is present in free form and contains at lea~t two isocyanate group4 while the 20~9~1 1 other of the two cap3ule wall-forming reaction components is present in reversibly blocked form and contains at least two reversibly blocked functional groups. The functional groups are deblocked by water and contain at least two NH groups or one NH
S qroup and one OH group. Both reaction components are present in the first or second liquid without reacting with one another. The reaction component which is present in reversibly blocked form is deblocked by means of water present in the first or second liquid and then reacts with the reaction component present in free form 1~ to form ~ polymeric capsule wall. The droplets of the first liquid or the solid particles are thus encapsulated in small capsules consisting of polymeric material.
Summary of tha In~ention It is an ob~ect of the present invent~on to provide a process for the formation of epoxy microcapsules having uniform wall thickneqs and capsule 8ize distribution. In-~itu polymerization of the microcapsules by the process of the present invontion results in microc~p~uleR highly suitable for usn in carbonless copying sy-~tem~.
In the proceE~s according to the present invention, microcap~ules sre produced by in-situ polymerization. Two wall-forming components, ~n apoxy and a ~etimine, ara provided within a first liquid. The fir~t liquid preferably contain~ a colorless dye precur~or or precursor mixture in an organic carrier solvent.
A stable disper~ion of droplets of the fir-qt liquid iR formed in a continuous phase of a second liquid. An oil/water emul~ion is ~Q~8~1 1 formed in the presence of an emulsifier, of which water is the main ingredient. Droplet sizes are determined by the emulsifier type and its concentration, emulsifLcation speed, time and temperature. The ketimine, which is incorporated together with an epoxy r~sin in the oil core discentinuouR phase, is hydrolyzed at the surface of the droplets by contact with the aqueous continuous phase to release a reactive amine. The released reactive amine then react~ with the epoxy resin to form polymeric capsule walls at the interface between the droplets of the fixst liquid and the aqueou~ continuous pha~e. The droplet-~ of the firqt liquid are encapsulated in capsules of epoxy.
Additional ob~ects and advantages of the invention will become apparent in the de~cription which follow~.
Brief D~scri~tion of the Drawinq~
Figura l i a scann~ng electron miCroQCOp~ photograph of a microcapsule di~persion of Versamine K-13, Araldite 6060 and KMC
oil at magnific~tions of 200X and 1000X.
Figure 2 i~ a scanning electron microscope photograph of a microcapsule dispersion of Versamine X-ll and Araldite 3337 at magnification~ of 200X and 1000X.
Figure 3 19 ~I scannlng electron microscope photograph of d microcapsule dlspersion of Versamine* K-ll and Araldite*6060 at magnifications of 200X and l000X.
Figure 4 i~ a scanning electron microscope photograph of a microcap~ule diqpersion of Ver~amine*X-ll and Araldite*3336 at magnifications of 200X and 1000X.
Trade-mark ~0~9~1 1 Figure S is a scanning electron microscope photograph of a microcapsule dispersion of Versamine K-12, Araldite 3337 and ~C/
Ucane at maqnifications of 200X and lOOOX.
Figure 6 is a scanning electron microscope photograph of a microcapsule dispersion of Versamine K-13, Araldite 3337 and ~UC/
Ucane.
Detailed DeseriPtion of the Preferred Embodiments The present invention relates to the microencapsulation of a core material in an epoxy microcapsule wall. The process employs two phases, a discontinuous phase tha~ forms the core materials to be encapsulated and a continuous pha~e. Within the core material phase i~ contained two wall-forming components, an epoxy resin and a ketimine. Upon hydrolysis of the ketimine, an amine is formed which is reactive with the epoxy resin.
Epoxy resins which are suitable for use in accordance with the present invention are the aromatic resins that contain multifunctional epoxide group~. For example, sisphenol A and Bisphenol F ba~ed glycidyl ethers, phenol and cre~ol based novolac re~ins, 1,1,2,2-(p-hydroxyphenol) ethane based glycidyl ether, ~-glycidyloxy-N,N-di-glycidyl aniline, methylolated bisphenol A
based re~in~, methylenedianiline based resin~, etc., are all useful in this invention. Preferably, bisphenol A and bisphenol F epoxy resinY are used.
_ g _ ~59~1 1 The bi~phenol A recin~ suitable for use in the instan invention preferably have an equivalent weight or WPE (weight pe_ epoxy) in the range of 175 to 500. Examples of suitable bisphenol A resins include Araldite 6005, 6010, 6020 and 6060, all from Ciba Geigy.
The bisphenol F resins suitable for use in the instant invention preferably have an equivalent weight or WPE in the range of 150-300. Examples of suitable bisphenol F resins include Araldite 281, 306, 3336 and 3337, all from Ciba Geigy.
XetimineQ ara amine-ketone adducts which are unreactive with epoxy resin. Upon release of amine through hydrolysis with water, the compound becomes reactive with epoxy resin. Ketimines which are 3uitable for use in accordance with the present invention correspond to the general formula:
H2NRNH2 + R'COR" -> R'R"C=NRN-CR'R"
wherein R iQ 2 lower alkyl radical, ~uch as methyl, ethyl, propyl, isopropyl, i~obutyl, ètc.
Preferably, ketimines of the following formulas are used.
R R
C = N - (CH2)2 - N ~ C (II) R H R
C a N - (CH2)2 - N ~ (CH2)2 ~ (III) 20~851 C = N - (CH2)2 - I ~ (CH2)2 ~ (IV) CH3 ~ CH2 c~3 CH - OH
o (~ .
wherein R is an isobutyl radical.
Other aliphatic amineR, such as hexamethylenediamine, dipropylenetriamine and triethylenetetra~ine c~n be reacted with methyl isobutyl ketone (MIBK) to form other ketimines which are suitable for use in the present invention. Examples of suitable ketimines are Versamine K-ll, ~-12 and R-13, all from Henkel Chemicals. Versamine K-11, K-12 and X-13 correspond to Formulas II, III and IV, respectively.
The rate of the reaction can be increased by the addition of a small amount of accelerator~ Acc~lerators which are suitable for u~e in ths pre~ent in~entlon include accelerator 399 (from Texaco chemicals)~ DMP-10 and DMP-30 (both from Rohm ~ Haas).
The discontiriuous phase contains at least one organic carrier solvent which contains at least one substance to be encapsula~ed, for example, a colorless dye or a colorles~ dye precur-~or. The organic carrier sol~ent should be capable of dissolving or ~uspending the dye precursor. Typical orsanic carrier solvents include alkyl naphthalene~, diarylalkane3, alkylated biphenyls, terphenyl~, linear alkyl benzenes and phthalate ester~.
~2.0~51 1 In COnnQction with carbonless copy systems, the fill material to be encapsulated within the inventive microcapsules will usually be a colorless dye precursor such as crystal violet lactone (CVL) benzoylleucomethylene blue (~LMB), rhodamine lactam, p-S toluene~ulfinatQ of Michler's hydrol (PTSMH), or any of the various chromogenic compounds that ara capable of changing from a colorless to a colored form on contact with reactive substances, such as phenolic resins or reactive clays.
Generally, once the ~ubstance to be encapsulated (i.e. the colorless dye precur~or or precurRor mixture) i~ di~solved in a carrier organic solvent, the solution can be mixed with the epoxy res$n and the ketimine compound. To thls 001ution can be added an emul~ification aqent which aids in the formation of a oil-in-water emulsion. Typical emul~ification agents include partially hydrolyzed polyvinyl acetate, such a~ Vinol 523 and 540 from Air Products and Chemlcals; sodium naphthalene sulfonate/formaldehyde condensate, such as Tamol~ L from Rohm & Haas Chemicals; gelatins, starch and cellulose derivatives such as carboxylated starch or celluloce, hydrcxyethyl cellulose, polyacrylamide, polystyrQnesulfon~te, etc. Suitable emul~ification agents are tho~e Rurface active chemical~ which contain both hydrophilic and hydrophobic groups in the same molecules. In an oil/water emulsion, thes~ molQcules adsorb at the oil-wat~r interface, prevent$ng the oll droplet~ from collap~ing into each other.
Particle size of the o$1 droplet~ can be ad~usted by emul~ification agent concentration, ~peed, temperature and time of agitation. Particle size~ in the range of 1-10 microns are most *
Trade-mark 20~98~1 1 suitable for çarbonless paper application~. Capsules useful for other applications may need ad~ustment of their sizes. During emulsification, the oil droplets are in a state of intermediate contact with water molecules. Consequently, a reactive amine is released due to the hydrolysis of the ketimine. The newly released reactive amino compound reacts with a nearby epoxy resin molecule in-situ. Upon completion of the reaction, microcapsules having epoxy walls and an encapsulated core material in an organic carrier solvent are formed. Warming of the emulsion slurry to about 60 to 95C, preferably to about 70-85C, accelerates the curing rate.
The present invention and some of its advantages are further illustrated, but not limited, by the following examples.
63 parts of a 6~ colorless dye in KMC oil were mixed with 8.11 parts of Araldite 6060, 0.97 parts of Versamine K-ll and 0.2~
parts of Accelerator 399. The mixture was emulsified in 130 parts of a 3% aqueou~ Tamol L/Vinol 523 (95:5) ~olution. The slurry was heated to 75C for four hours. Under 3canning electron microscope, spherical microcapsules were obtained. Average particle size was about 5 microns. The capsule slurry was coated as a CB sheet. When it wa~ written against a phenolic resin coated receiving sheet, a clear black image was obtzined.
20598~1 1 EXAMPL~ 2 63 parts of a 6~ colorless dye in KMC oil were mixed with 6.87 parts of Araldite 3336, 2.20 parts of Versamine ~-11 and 0.20 parts of Accelerator 399. The mixture was emulsified in 130 parts of a 3~ aqueous Tamol LtVinol 523 (95:5) solution. The slurry was heated to 75C for four hour~. Under scanning electron microscope, spherical microcapsules were obtained. Average particle size was about 6 microns. The capsule slurry was coated as a C3 sheet. When it was written against a phenolic resin coated receiving sheet, a clear black image was obtained.
, .
63 parts of a 63 colorless dye in KMC oil were mixed with 7.0 parts of Araldite 3337, 2.07 parts of Versamine K-ll and 0.20 parts of Accelerator 399. The mixture was emulsified in 130 parts of a 3~ aqueous Tamol L/Vinol 523 (95:5) olution. The slurry was heated to 75C for four hours. Under scanning electron microscope, spherical microcapqules were obtained. Average particle size was about 4 microns. The capsule ~lurry was coated a9 a CL sheet. When it was written against a phenolic resin coated receiving shcet, a clear black image was obtained.
E~AMPL~ 4 * *
63 parts of a 6~ colorless dye in Sure~ol 330/Ucane 11 (50s50) ~olution were mixed wlth 6.98 parts of Araldite 6010, 2.09 parts of Versamine X-12 and 0.21 part~ of Accelerator 399. The mixture was emulsified in 130 parts of a 3~ aqueous Tamol L/Vi,sol Trade~mark 2~5~8~
1 523 (95:5) solution. The slurry was heated to 75C for feur hours. Under scanning electron microscope, spherical microcapsules were obtained. Average particie size was about 5 microns. The capsule slurry was overcoated onto a phenolic resin coated receiving sheet. Under writing pressure, a clear black image was obtained.
63 parts of a 6% colorless dye in Suresol 330/Ucane 11 (50:s0) solution were mixed with 8.1 parts of Araldite 6060, 0.98 parts of versamine ~-12 and 0.1 parts of Accelerator 399. The mixture was emul~ified in 130 parts of a 3~ aqueou-~ Tamol L/Vinol 523 (95:5) solution. The slurry was heated to 75C for four hours. Under scanning electron microscope, spherical microcapsules were obtained. Average particle size was about ~.5 microns. The cap~ule slurry was overcoated onto a phenolic resi~
coated receiving sheet. Under writing pressure, a clear black image was obtained.
63 parts of a 6% colorless dye in Suresol 330/Ucane 11 (50:50) ~olution were mixed with 6.86 parts of Araldite 281, 2.22 parts of VerYamine X-12 and 0.22 parts of Accelerator 399. The m$xture waq emulsified in 130 parts of a 3% aqueous Tamol L/Vi-.^l 523 (95:5) solution. The ~lurry wa~ heated to 75C for four hours. Under scanning electron microscope, spherical microcapsules were obtained. Average particle size was about ~5~5~
1 microns. The capsule slurry was overcoated onto a phenoli~ -esin coated receiving sheet. Under writing pressure, a clear bla-k image was obtained.
~A~PLE 7 - 63 parts of a 6% colorless dye in KMC/Ucane 11 (50:50) solution were mixed with 6.86 parts of Araldite 3336, 2.24 parts of Versamine K-12 and 0.22 parts of Accelerator 399. The mix.ure was emulsified in 130 parts of a 3% aqueous Tamol L/Vinol 523 10- (95:5) solution. The slurry was heated to 75C for four hours.
Under qc~nning electron microscope, Ypherical microcapsuleq were obtained. Average particle size was about 4 micron~. The capsule slurry was overcoated onto a phenolic resin coated receiving sheet. Under writing pressure, a clear black image was obtained.
~XA~PLE 8 63 parts of a 6~ colorless dye in Suresol 330/Ucane 11 t50:50) solution were mixed wlth 6.47 parts of Araldite 6010, 2.'6 parts of Versamine X-13 and 0.2 parts of Accelerator 399. The mixture wa~ emulsified in 130 parts of a 3~ aqueou~ Tamol L/Vinol 523 t95:5) solution. The slurry was heated to 75C for four hours. Under scanninq electron microscope, spherical microcapsules were obtained. Average particle size was about ~.5 microns. The cap~ule slurry was overcoated onto a phenolic resln coated receiving sheet. Under writing pre~sure, a clear blac~
image was obtained.
2~8~
1 , EXAMPLE 9 63 parts of a 6~ colorless dye in Suresol 330/Ucane 11 (s0:50) solution were mixed with 6.26 parts of Araldite 281, 2.82 parts of versamine X-13 and 0.21 parts of Accelerator 399. The mixture was emulsified in 130 parts of a 3% aqueous Tamol L/Vinol 523 (95:5) solution. The slurry was heated to 75C for four hours. Under scanning electron microscope, spherical microcapsules were obtained. Average particle size was about 5 microns. The capsule slurry was overcoated onto a phenolic resin coated receiving sheet. Under writing pressure, a clear black image was obtained.
63 parts of a 6~ colorless dye in KMC/Ucane 11 (50:50) solution were mixed with 6.36 parts of Araldite 3337, 2.72 parts of versamine R-13 and 0.2 parts of Accelerator 39g. The mixture was emulsified in 130 parts of a 3~ aqueous Tamol L/Vinol 523 (95:5) qolution. The slurry was heated to 75C for four hours.
Under scanning electron microscope, spherlcal microcapsules were obtained. Average particle size was about 4 microns. The capsule slurry wa~ overcoated onto a phenolic resin coated receivinq sheet. Under writing pressure, a clear black image was obtained.
Although the pre~ent invention has been described in connection with the preferred embodiments, it is to be understood that modlficstion~ and variations may be resorted to without - 17 _ ~OS98~1 departing from the spirit and scope of the invention. Such modifications are considered to be within the purview and s~cpe o.
the inven~ion and the appended claims.
Claims (28)
1. A process for producing microcapsules by in-situ polymerization comprising:
providing two capsule wall-forming reaction components within a first liquid, wherein said reaction components are an epoxy resin and a ketimine; and forming a stable dispersion of droplets of said first liquid in an aqueous continuous phase of a second liquid;
wherein said ketimine is hydrolyzed at the surface of the droplets by contact with said aqueous continuous phase to release a reactive amine, said reactive amine thereby contacting the epoxy resin to form polymeric capsule walls at the interface between the droplets of the first liquid and the aqueous continuous phase, the droplets of the first liquid being encapsulated in capsules of epoxy.
providing two capsule wall-forming reaction components within a first liquid, wherein said reaction components are an epoxy resin and a ketimine; and forming a stable dispersion of droplets of said first liquid in an aqueous continuous phase of a second liquid;
wherein said ketimine is hydrolyzed at the surface of the droplets by contact with said aqueous continuous phase to release a reactive amine, said reactive amine thereby contacting the epoxy resin to form polymeric capsule walls at the interface between the droplets of the first liquid and the aqueous continuous phase, the droplets of the first liquid being encapsulated in capsules of epoxy.
2. The process of claim 1, wherein said first liquid is an organic carrier solvent containing a colorless dye or precursor thereof.
3. The process of claim 1, wherein said first or second liquid further contains an accelerating agent.
4. The process of claim 1, wherein the epoxy resin is bisphenol A or bisphenol F based glycidyl ether resin.
5. The process of claim 4, wherein the epoxy resin is bisphenol A based glycidyl ether resin.
6. The process of claim 5, wherein the bisphenol A based glycidyl ether resin has a weight per epoxy within the range of 175-500.
7. The process of claim 4, wherein the epoxy resin is bisphenol F based glycidyl ether resin.
8. The process of claim 7, wherein the bisphenol F based glycidyl ether resin has a weight per epoxy in the range of 150-300.
9. The process of claim 1, further comprising heating said stable dispersion to 70-85° C to accelerate the curing rate of the epoxy.
10. A process for forming microcapsules comprising;
dissolving a colorless dye precursor or precursor mixture in an organic carrier solvent;
mixing the resulting solution with an epoxy resin and a ketimine compound emulsifying the resulting solution in the presence of an emulsification agent to form an oil-in-water emulsion;
the oil droplets in the emulsion thereby coming into contact with water molecule to release a reactive amine through hydrolysis of the ketimine, said reactive amine then reacting with the epoxy resin to form microcapsules having epoxy walls.
dissolving a colorless dye precursor or precursor mixture in an organic carrier solvent;
mixing the resulting solution with an epoxy resin and a ketimine compound emulsifying the resulting solution in the presence of an emulsification agent to form an oil-in-water emulsion;
the oil droplets in the emulsion thereby coming into contact with water molecule to release a reactive amine through hydrolysis of the ketimine, said reactive amine then reacting with the epoxy resin to form microcapsules having epoxy walls.
11. The process of claim 10, wherein the microcapsules are 1-10 microns.
12. The process of claim 10, further comprising heating the emulsion to 70-85°C to accelerate the cure rate.
13. The process of claim 10, wherein the epoxy resin s bisphenol A or bisphenol F based glycidyl ether resin.
14. The process of claim 13, wherein the epoxy resin is bisphenol A based glycidyl ether resin.
15. The process of claim 14, wherein the bisphenol A based glycidyl ether resin has a weight per epoxy within the range of 175-500.
16. The process of claim 13, wherein the epoxy resin is bisphenol F based glycidyl ether resin.
17. The process of claim 16, wherein the bisphenol F based glycidyl ether resin has a weight per epoxy in the range of 150-300.
18. A process of making microcapsules for use in carbonless paper comprising:
incorporating a colorless dye or precursor thereof and a carrier solvent within a capsule member, wherein said capsule member is formed by reacting an epoxy resin together with a ketimine in the presence of said colorless dye, said carrier solvent and water.
incorporating a colorless dye or precursor thereof and a carrier solvent within a capsule member, wherein said capsule member is formed by reacting an epoxy resin together with a ketimine in the presence of said colorless dye, said carrier solvent and water.
19. The process of claim 18, wherein the epoxy resin is bisphenol A or bisphenol F based glycidyl ether resin.
20. The process of claim 19, wherein the epoxy resin is bisphenol A based glycidyl ether resin.
21. The process of claim 20 wherein the bisphenol A based glycidyl ether resin has a weight per epoxy in the range of 175-500.
22. The process of claim 19, wherein the epoxy resin is bisphenol F based glycidyl ether resin.
23. The process of claim 22, wherein the bisphenol F based glycidyl ether resin has a weight per epoxy in the range of 150-300.
24. The process of claim 18, wherein the microcapsules are 1-10 microns in size.
25. A process for producing microcapsules by in-situ polymerization comprising:
forming a stable dispersion of droplets of a first liquid in a continuous phase of a second liquid by emulsification, said dispersion containing two capsule wall-forming reaction components, which are an epoxy resin and a ketimine;
introducing water to said dispersion to cause a reactive amine to be released by hydrolysis of the ketimine, said reactive amine contacting the epoxy resin to form polymeric capsule walls at the surface of the droplets of the first liquid, the droplets of the first liquid being encapsulated in capsules of epoxy.
forming a stable dispersion of droplets of a first liquid in a continuous phase of a second liquid by emulsification, said dispersion containing two capsule wall-forming reaction components, which are an epoxy resin and a ketimine;
introducing water to said dispersion to cause a reactive amine to be released by hydrolysis of the ketimine, said reactive amine contacting the epoxy resin to form polymeric capsule walls at the surface of the droplets of the first liquid, the droplets of the first liquid being encapsulated in capsules of epoxy.
26. The process of claim 1, wherein the epoxy resin is an aromatic epoxy resin containing two or more epoxide groups and having an equivalent weight of 175 to 500.
27. The process of any one of claims 1 to 26, wherein the ketimine is a reaction product of (1) a ketone of the formula R'-CO-R" with (2) an amine selected from the group consisting of a diamine of the formula: H2N-R-NH2 (wherein R' and R" are each a lower alkyl and R is (CH2)2, (CH2)2-NH-(CH2)2, or a residue of hexamethylenediamine), dipropylenetriamine and triethylenetetramine.
28. The process of any one of claims 1 to 26, wherein the ketimine is represented by the formula:
(II) (III) or (IV) (wherein R is an isobutyl radical).
(II) (III) or (IV) (wherein R is an isobutyl radical).
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US65401891A | 1991-02-12 | 1991-02-12 | |
| US07/654,018 | 1991-02-12 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2059851A1 true CA2059851A1 (en) | 1992-08-13 |
Family
ID=24623166
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2059851 Abandoned CA2059851A1 (en) | 1991-02-12 | 1992-01-22 | In-situ polymerization process for producing epoxy microcapsules |
Country Status (3)
| Country | Link |
|---|---|
| JP (1) | JPH0568872A (en) |
| AU (1) | AU641846B2 (en) |
| CA (1) | CA2059851A1 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2006159194A (en) * | 2001-07-19 | 2006-06-22 | New Industry Research Organization | Method for manufacturing target component-encapsulated fine particle and hollow polymer fine particle and method for manufacturing it |
| JP6868916B1 (en) * | 2020-04-28 | 2021-05-12 | エレテン株式会社 | Sterilizing nanocapsules, grape-like fine particle aggregates, disinfecting sterilizing filters and manufacturing methods thereof |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6017573B2 (en) * | 1977-05-04 | 1985-05-04 | 神崎製紙株式会社 | Manufacturing method of microcapsule aqueous dispersion |
| US4356108A (en) * | 1979-12-20 | 1982-10-26 | The Mead Corporation | Encapsulation process |
| US5015527A (en) * | 1989-01-13 | 1991-05-14 | Moore Business Forms, Inc. | Interfacial epoxy microcapsulation system |
-
1992
- 1992-01-22 CA CA 2059851 patent/CA2059851A1/en not_active Abandoned
- 1992-02-11 AU AU10852/92A patent/AU641846B2/en not_active Ceased
- 1992-02-12 JP JP4058902A patent/JPH0568872A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0568872A (en) | 1993-03-23 |
| AU1085292A (en) | 1993-03-18 |
| AU641846B2 (en) | 1993-09-30 |
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