# US 4,396,670 A · Process for the production of microcapsules

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- Number: US 4,396,670 A
- Document ID: US4396670A
- Status: Granted
- Kind: A
- Application number: 06/247,150
- Filed: 1981-03-24
- Granted: 1983-08-02
- Earliest claimed: 1980-04-08
- Assignees: The Wiggins Teape Group Limited
- Inventors: Peter Sinclair
- Web page: https://patentgrep.com/patent/US4396670A

## CPC

- B41M 5/165: characterised by the use of microcapsules; Special solvents for incorporating the ingredients
- B01J 13/18: In situ polymerisation with all reactants being present in the same phase
- Y10T 428/249997: Encapsulated liquid
- B41M: PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING, (correction of typographical errors B41J; processes for applying transfer pictures or the like B44C1/16; fluid media for correction of typographical errors by coating C09D10/00; printing textiles D06P)
- B01J: CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

In a process for the production of microcapsules containing a liquid fill material, a dispersion-stabilizing species is produced in an aqueous acidic medium by interaction of a melamine formaldehyde precondensate and a water soluble polymer, neither of which alone is dispersion stabilizing with respect to the liquid fill material, and the precondensate is condensed by acid catalysis to produce a condensate which separates from solution and enwraps the liquid fill material to produce microcapsules.

## Claims

### Claim 1

A process for the production of microcapsules containing a liquid fill material, comprising the steps of:
establishing an aqueous medium which is at an acidic pH and which contains both a melamine formaldehyde precondensate condensable at said acidic pH and a polymer which contains at least one acid, amide, amine, imine, ester, ether, hydroxyl, urethane, thiol or mercaptan group, said melamine formaldehyde precondensate interacting with said polymer in the absence of any substantial amount of urea formaldehyde precondensate to form a species which imparts dispersion-stabilizing properties to the liquid fill material, neither said melamine formaldehyde precondensate nor said polymer alone being dispersion-stabilizing with respect to the liquid fill material at the conditions at which a stable dispersion is to be established;
establishing a stable dispersion of liquid fill material in the aqueous medium after formation of said dispersion stabilizing species; and
condensing said melamine formaldehyde precondensate by acid catalysis after formation of said dispersion to produce a melamine formaldehyde condensate which separates from solution and enwraps the dispersed liquid fill to produce said microcapsules.

### Claim 2 (depends on 1)

A process according to claim 1 wherein said melamine formaldehyde precondensate is a methylated melamine formaldehyde precondensate.

### Claim 3 (depends on 1)

A process as claimed in claim 1 wherein said water soluble polymer is an acrylamide/acrylic acid copolymer, starch or a starch derivative, hydroxyethyl cellulose carboxymethyl cellulose, an alginate, a polyurethane, polyethylene oxide, polypropylene glycol, a polyquaternary amine, a polyamide polyamine epichlorohydrin resin, polyethyleneimine or xanthan gum.

### Claim 4

A process as claimed in any preceding claim wherein said acidic pH is in the range 3.9 to 5.5.

### Claim 5 (depends on 1, 2, 3)

A process as claimed in any of claims 1, 2 or 3 where the precondensate is partially condensed in the presence of the polymer to produce the dispersion stabilising species.

### Claim 6 (depends on 1, 2, 3)

A process as claimed in any of claims 1, 2 or 3 wherein the dispersion stabilising species is formed without initial partial condensation in the presence of the polymer.

### Claim 7 (depends on 1, 2, 3)

A process as claimed in any of claims 1, 2 or 3 wherein the weight ratio of said polymer to said precondensate is in the range 0.03:5 to 5:1.

### Claim 8 (depends on 1, 2, 3)

A process as claimed in any of claims 1, 2 or 3 wherein once a stable dispersion has formed the temperature is raised to accelerate the condensation reaction.

### Claim 9 (depends on 1, 2, 3)

A process as claimed in any of claims 1, 2 or 3 wherein the weight ratio of liquid fill material droplets to microcapsule wall precursor material in aqueous acidic medium is in the range of 4.5:1 to 20:1.

### Claim 10 (depends on 1, 2, 3)

A process as claimed in any of claims 1, 2 or 3 wherein additional melamine formaldehyde precondensate is added after formation of a stable dispersion.

### Claim 11 (depends on 1, 2, 3)

Microcapsules produced by a process as claimed in any of claims 1, 2 or 3.

### Claim 12 (depends on 11)

A sheet material carrying microcapsules as claimed in claim 11.