Microcapsule and process for their production

• US 4,533,599 A
• Filed: 03/23/1984
• Issued: 08/06/1985
• Est. Priority Date: 03/25/1983
• Status: Expired due to Fees

• Current Assignee: Mitsubishi Paper Mills Limited
• Original Assignee: Mitsubishi Paper Mills Limited
• Inventors: Kawai, Akira, Okumura, Fumio
• Primary Examiner(s): Lovering, Richard D.
• Application Number:
  US06/592,845
• Time in Patent Office: 501 Days
• Field of Search: 264/4.7, 427/213.34, 428/402.21, 428/402.24
• US Class Current: 428/402.21
• CPC Class Codes: B01J 13/18 In situ polymerisation with all reactants being present in the same phase
• CPC Class Codes: B41M 5/165 characterised by the use of microcapsules; Special solvents for incorporating the ingredients
• CPC Class Codes: Y10T 428/2985 Solid-walled microcapsule from synthetic polymer
• CPC Class Codes: Y10T 428/2989 Microcapsule with solid core [includes liposome]

Abstract

By using, in production of microcapsules, a partially esterified product of a styrene-maleic anhydride copolymer as an emulsifier, advantages are obtained that coloring of emulsion can be reduced/prevented at the time of emulsification and, when the microcapsules produced are used in a carbonless copying paper, a desensitizer component is not transferred to a lower paper and accordingly color development is not hindered.

Claims

1. A process for producing microcapsules containing a hydrophobic material as a core material, the process comprising the steps of dispersing or emulsifying a hydrophobic material in the form of discontinuous microparticles in an acidic aqueous solution containing a partially esterified product of a styrene-maleic anhydride copolymer, the partially esterified product of a styrene-maleic anhydride copolymer being used in a quantity of 2 to 20 parts by weight relative to 100 parts by weight of the hydrophobic material, adding a melamine-formaledhyde precondensate to the dispersion or emulsion obtained, and subjecting the resuting mixture to reaction in an acidic phase with heating to form a shell film on each microparticle.

2. A process for producing microcapsules according to claim 1, wherein the ester group of the partially esterified product of a styrene-maleic anhydride copolymer is selected from those having an alkyl group of 1 to 10 carbon atoms or an aralkyl group.

3. A process for producing microcapsules according to claim 1, wherein the esterification degree of the partially esterified product of a styrene-maleic anhydride copolymer is 50% or lower relative to total carbonyl group number.

4. A process for producing microcapsules according to claim 3, wherein the esterification degree is 5 to 50%.

5. A process for producing microcapsules according to claim 1, wherein the partially esterified product of a styrene-maleic anhydride copolymer is obtained by copolymerizing styrene monomer, maleic anhydride and a required quantity of a mono- or di-ester of maleic acid or by partially esterifying a styrene-maleic anhydride copolymer.

6. A process for producing microcapsules according to claim 1, wherein the melamine-formaldehyde precondensate is obtained by reacting melamine with formaldehyde in a molar ratio of 1 (the former)/1.5 (the latter) or in a lower molar ratio.

7. A process for producing microcapsules according to claim 6, wherein the molar ratio is 1/2 to 1/3.

8. Microcapsules produced by the process defined in claim 1.