CA1277553C - Amine-formaldehyde microencapsulation process - Google Patents

Amine-formaldehyde microencapsulation process

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Publication number
CA1277553C
CA1277553C CA000499652A CA499652A CA1277553C CA 1277553 C CA1277553 C CA 1277553C CA 000499652 A CA000499652 A CA 000499652A CA 499652 A CA499652 A CA 499652A CA 1277553 C CA1277553 C CA 1277553C
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CA
Canada
Prior art keywords
formaldehyde
polyol
core material
amine
urea
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
CA000499652A
Other languages
French (fr)
Inventor
David G. Adkins
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Mead Corp
Original Assignee
Mead Corp
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Filing date
Publication date
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Application granted granted Critical
Publication of CA1277553C publication Critical patent/CA1277553C/en
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Classifications

    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08GMACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G12/00Condensation polymers of aldehydes or ketones with only compounds containing hydrogen attached to nitrogen
    • C08G12/02Condensation polymers of aldehydes or ketones with only compounds containing hydrogen attached to nitrogen of aldehydes
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01JCHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J13/00Colloid chemistry, e.g. the production of colloidal materials or their solutions, not otherwise provided for; Making microcapsules or microballoons
    • B01J13/02Making microcapsules or microballoons
    • B01J13/06Making microcapsules or microballoons by phase separation
    • B01J13/14Polymerisation; cross-linking
    • B01J13/18In situ polymerisation with all reactants being present in the same phase
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08GMACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G12/00Condensation polymers of aldehydes or ketones with only compounds containing hydrogen attached to nitrogen
    • C08G12/02Condensation polymers of aldehydes or ketones with only compounds containing hydrogen attached to nitrogen of aldehydes
    • C08G12/40Chemically modified polycondensates
    • C08G12/42Chemically modified polycondensates by etherifying
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08GMACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G14/00Condensation polymers of aldehydes or ketones with two or more other monomers covered by at least two of the groups C08G8/00 - C08G12/00
    • C08G14/02Condensation polymers of aldehydes or ketones with two or more other monomers covered by at least two of the groups C08G8/00 - C08G12/00 of aldehydes
    • C08G14/04Condensation polymers of aldehydes or ketones with two or more other monomers covered by at least two of the groups C08G8/00 - C08G12/00 of aldehydes with phenols
    • C08G14/06Condensation polymers of aldehydes or ketones with two or more other monomers covered by at least two of the groups C08G8/00 - C08G12/00 of aldehydes with phenols and monomers containing hydrogen attached to nitrogen

Abstract

Abstract of the Disclosure A process for producing amine-formaldehyde micro-capsules wherein the reaction of the amine and formaldehyde to form the microcapsule wall is carried out in the presence of a polyol as a systems modifier.

Description

~277553 MD.Y 079 P2 -1-AMINE-FORMALDEHYDE MICROENCAPSUhATION PROCESS

Back~ound of tne Invention Tne present invention relates to a process for forming microcapsules whereln the microcapsule wall is formed from an amine-formaldehyde resin. More particular-ly, it relates to a process for forming urea-formaldehyde microcapsules wherein the urea-formaldehyde resin is condensed in the presence of a polyol.
U.~. Patents 4,089,802 and 4,001,140 describe a process for producing urea-formaldehyde microcapsules wherein the capsule wall is formed in the presence of a negatively charged polyelectrolyte. Tha~ polyelectrolyte is a carboxyl-substituted, linear aliphatic material. The function of the polyelectrolyte is that of a system modi-fier. The polyelectrolyte reportedly controls the forma-- tion of the condensation polymer such that the encapsula-tion process can be carried out without continually dilut-ing the encapsulation medium as reportedly is required with earlier processes. The function of the modifier is reflected in a reduction in the viscosity of the system at higher polymer concentrations.
The system modifiers disclosed in U.S. Patents 4,089,802 and 4,001,140 are maleic anhydride copolymers.
Representative examples are isobutylene-maleic anhydride copolymer, ethylene~maleic anhydride copolymer, propylene-maleic anhydride copolymer, and butadiene-maleic anhydride copolymer. The molecu~ar weight of tAese materials must exceed a certain minimum molecular weight to avoid gelling or thickening of tne encapsulation medium.

i;~77S53 MDX 073 P2 -~-Summary of the Invention The present invention resides in the discovery of a class of materials wnich are effective system modifiers for the formation of amine-formaldehyde microcapsules.
The process of the present invention provides for tne formation of capsule walls from the condensation of formaldehyde and an amine sucn as urea, dimethyiol urea, methylated dimethylol urea, or melamine in the presence of a polyol as a system modifier. The system modifier is present in dissolved form in the continuous aqueous phase of the encapsulation medium. Encapsulation proceeds via liquid-liquid phase separation. As the amine and formal-dehyde react in tne aqueous phase, the polymer builds to a molecular weight where it is no longer soluble and precip-itates around the dispersed particles of core material which are oily or oleophilic materials. Tne polymer hardens upon furtner reaction and an impermeable micro-capsule is obtained.
The process of the invention typically involves forming an agitating aqueous solution of the systems modifier having the core material dispersed therein and, while maintaining the dispersion, adding solutions of the amine and formaldehyde thereto. On reaction, an amine-formaldehyde condensate separates from the solution which wets and enwraps the capsule core material. After the walls have belen solidified, the capsules may be separated from the medium and washed.
The order of addition of the system modifier and the amine and formaldehyde solutions is important but open to ~ubstantial variation. In another embodiment, an aqueous solution of amine and the system modifier may be prepared before the core material is dispersed therein.
The formaldehyde solution is then added and upon heatin~, the polymer forms, separates from solution and enwraps tne core material.
A further alternative is to form an aqueous syste.n containing the systems modifier and a water-soluDle, urea-formaldehyde or melamine-formaldehyde precondensate (or prepolymer~, into wnich ~he core material is ~ispersed.
The precondensate is then reacted to form the resin which encapsulates tne core material. As a practical matter, the capsule components can be mixed in any order provided tAat the polyol is present at the time the condensation reaction begins.
Because the order of addition of the encapsulation agents can vary, the present invention is most basicalLy defined by reference to the encapsulation system as it exists immediately prior to forming the microcapsules.
That system includes a continuous aqueous phase having tAe - polyol and amine, formaldehyde, or an amine-formaldehyde pre~condensate dissolved therein, and a dispersed phase of the intended core material.
One method in accordance with the present inven-tion involves the following steps:
(i) preparing an aqueous solution containing the polyol, (ii) emulsifying the core material therein, (iii) adding the amine to the system, (iv) adding formaldehyde to the system, (v) adding the acid catalyst, (vi) polymerizing the urea and formaldehyde while stirring the system, (vii) heating, and (viii) reacting the excess formaldehyde.
The process is flexible. The amine could be added in step (i), (iv), (v) or (vi). The system modifier could be :~277S53 a~ed in steps (ii.i), (iv) or (v~, and the acid catalyst could De added in step (i), (iii) or (iv).
Another process involves ~he following sequence of steps:
(i) emulsifying an oil in an aqueous acid solution containing a polyol, (ii) adding an aqueous solution of tne amine, ~iii) adding an a~ueous solution of resorcinol, (iv) adding an aqueous solution of formalde-hyde, (v) heating to 65C, (vi) adjusting the pH to 9.0, (vii) adding a solution oE sodium acid sulfite to scavenge excess formaldehyde, and (viii) removiny an aqueous dispersion of tne microcapsules. :

Detailed Description of the Invention ~hile the discussions herein frequently make reference to the use of urea, it will be understood that urea derivatives such as dimethylol urea, methylated dimethylol urea, etc. as well as other amines such as melamine may also be used.
Polyols which are preferred for use in the present invention are low molecular weight ~molecular weight less than 500) materials having three or more hydroxyl groups.
A particularly preferred class of polyols are tetrahydroxy-alkyl alkylenediamines of the formula R~ R
~N--A--H~
R ~R

lZ77~iS3 wnere each R represents a hydroxyalkyl group having l to 6 CarDOn atoms and A is an al~ylene bridge having l tv 4 carbon atoms. The respective R groups may be tne same or different but are frequently the same in commercially availaDle products. A particularly preferr~d polyol is N,N,N',N'-tetraKis(2-nydroxypropyl) etnylenediamine wAich is col~mercially available under the trademark QUADROL from BASF Wyandotte Corporation.
Polyols can be used alone or in combination with other systems modifiers such as the maleic anhydride copolymers mentioned above. Another modifier useful in comDination with polyols is pectin or polygalacturonic acid.
The condensation reaction proceeds under acid conditions, e.g., pH of 7.0 or less; Aowever, the reaction is preferably carried out at a pH in the range of 2.5 to 5Ø The temperature of the encapsulation medium snould be maintained at about l0 to 95C, preferably about 25 to 85C and more preferably about 45 to 75C.
Among the acid catalysts that may be used are low moleculae weight carboxylic acids, e.g., formic acid, acetic acid, etc.; inorganic acids, e.g., sulfuric acid, hydrochloric acid, phosphoric acid, etc.; and acidic or easily hydrolyzable salts such as aluminum sulfate, ammon-ium nitrate, ammonium chloride, ammonium sulfate, etc.
Ammonium salts are preferred as they seem to provide a stronger and less permeable capsule. Tne ammonium salts are usually employed in an amount of about 2 to 20% by weight based on the amoun~ of urea.
Urea and formaldehyde are preferably present in the encapsulation medium, whether as the free monomer or a precondensate, in a molar ratio of formaldehyde to urea of at least 1.5 and preferably about 2.0 to 3Ø

- :

~Z77553 rO reduce malodor and tAe incidence of skin irritation, wnen the polymerization reaction is complete, it is desirable to remove or react tne excess form~ldehy~e.
This can be accomplished by using any one of several known techniques such as the addition of phosphoric acid, urea, sulfite or bisulfite. These materials react with the - formaldehyde to form a product which is easily removed from tne medium. The addition of the urea or sodium sulfite to scavenge formaldenyde is preferably made in a single step after encapsulation and prior to storage. The pH and temperature of the medium snould be adjusted for this reaction. The sulfite is preferably reacted at a pH
of 6 to 8 at room temperature for about 2 hours. The urea can be reacted at a p~ of 3 to 5 or 8 to 12 at a tempera-ture of 30 to 60C for 4 hours.
A polyhydric phenol may be added to the reaction system for co-condensation with the urea and formaldenyde to improve permeability as desired. Suitable phenols are resorcinol, catechol, gallic acid, and the like. The phenols may be added in an amount of about 5 to 30% by weight based on the amount of urea.
Microcapsules prepared in accordance with the present invention are particularly advantageous for use in pressure-sensitive papers or photographic papers of the type described in U.S. Patents 4,399,209 and 4,440,846 to Sanders et al. For these applications, the microcapsules preferably have a size of about l to 20 microns, mvre preferably l.5 to lO microns and most preferably 2 to 8 microns.
In some cases it may be desiraDle tv use an emulsion stabilizer in the encapsulation. Tnese are materials which form a thin layer around the capsule core ~Z77~3 ~X 079 P2 -7-entities and thereby stabilize the emulsion. Certain surfactants can be used for tnis purpose but, in particu-lar, it may ~e desirable to add a polyisocyanate to tne core material. This practice is described in detail in U.~. Patent 4,353,809. Tne polyisocyanate is believed to react with water at the interface of the core material and the aqueous medium and form a thin layer of polymer which stabilizes the emulsion. Preferred polyisocyanates are SF-50, an aromatic triisocyanate manufactured by Union Carbide and N-lO0, a biuret of hexametnylene diisocyana~e and water manufactured by Mobay Cnemical Co. The isocyan-ate is typically added in an amount of about 0.005 to 3 parts per lO0 parts of the core material and preferably O.Ol to 2 parts.
The capsule core material will vary with the function of the microcapsules. Core materials convention-ally used in the carbonless paper art are also useful in the present invention. The materials include a color former and optionally an oil solvent. The encapsulation process of the present invention is particularly useful in forming photosensitive microcapsules as described in the aforementioned Sanders et al. patents. In these emoodi-ments, the core material may be a combination of a ph~to-sensitive composition and a color former.
The invention will be illustrated in more detail by the following example.

Example l An aqueous phase was prepared by placing llOg water and 4.7g N,N,N',N'-tetrakis(~-ny~roxypropyl) ethylenediamine in a steel beaker under an overhead mixer carrying a six blade impeller. The solution was stirred ~775~3 MDX 07~ P2 -8-until the diamine dissolved and 3.lg sigma pectin was added with stirring. Then, 0.06259 of cetyldimethyletnyl-ammonium bromide was added and the pH of the solution was adjusted to 4.0 witn the addition of 20~ H2SO4.
An oil phase containing 50g trimetnylolpropane triacrylate (T~PTA), 3g Crystal Violet Lactone (CVL), and 5.lg of a photoinitiator system was prepared and 3.29 SF-50 and 6.6g N-100 was added thereto.
The oil phase was emulsified into the aqueous phase with stirring at 3,000 rpm over a period of ~0 minutes. The rate of stirring was reduced to 2,000 rpm and the following solutions were added at 2 minute inter-vals in order: (i) 16.6g of 50~ urea, ~ii) 0.8g of resor-cinol in 5.09 water, (iii) 2l.4g of 37% aqueous formalde-hyde, and (iv) l.5g of 40~ ammonium sulfate. After stir-ring for 5 minutes at room temperature, the temperature of the emulsion was increased to 65C and cured for 2 hours.
The pH of the emulsion was then adjusted to 9.0 by adding 20~ NaOH. To react excess formaldehyde, 2.8g of sodium bisulfite was added and tne e,nulsion was allowed to cool to room temperature with stirring.

Example 2 An aqueous phase was prepared consisting of ll0g water and 9.4g N,N,N',N'-tetrakis(2-hydroxypropyl) ethylenediamine. After stirring to dissolve the diamine, 3.lg of sigma pectin was added with stirring. The pH of the solution was then adjusted to 4.0 with the addition of 60% HzsO4.
An oil phase was prepared consisting of 509 TMPTA, 3.09 CVL and 5.19 of a photoinitiator system. The oil phase was emulsified into the aqueous phase with .
, .

~Z77553 M~X 073 P2 -9-s~irring at 3,000 rpm for lO ,ninutes. Stirring was reduced to 2,000 rpm and solutions (i)-(iv) from Example l were added at 2 minute intervals. Tne resulting emulsion was stirre~ at room temperature for 6 minutes and tne tempera-ture was then raised to 65C for 2 hours. Tne pH of tne emulsion was adjusted to 9.0 and sodium bisulfite was tAen added as in Example l above.
Having described tne invention in detail and b~
reference to preferred embodiments thereof, it will be apparent that modifications and variations are possible without departing from the scope of the invention defined in the appended claims.
What is claimed is:

Claims (13)

1. A process for producing microcapsules which comprises:
forming an agitating aqueous system having dis-crete particles of an oily core material dispersed therein, said aqueous system being a solution of a polyol and an amine or an amine-formaldehyde precondensate, and condensing formaldehyde with the amine to form a condensation product which is insoluble in said system and which forms a solid capsule wall surrounding said particles of core material.
2. The process of claim 1 wherein said polyol has a molecular weight less than about 500 and and three or more hydroxyl groups.
3. The process of claim 2 wherein said polyol has the structural formula where A is an alkylene bridge having 1 to 4 carbon atoms and each R represents a hydroxyalkyl group having 1 to 6 carbon atoms.
4. The process of claim 3 wherein said polyol is N,N,N',N'-tetrakis(2-hydroxypropyl) ethylenediamine.
5. The process of claim 4 wherein said condensation product is a urea-formaldehyde resin.
6. The process of claim 4 wherein said condensation product is melamine-formaldehyde resin.
7. The process of claim 1 wherein said process further comprises adding a solution containing a polyhydric phenol to said aqueous system.
8. The process of claim 1 wherein after forming said microcapsules, said process comprises the additional step of reacting any excess formaldehyde to remove it.
9. A process for producing microcapsules which comprises:
establishing an agitating aqueous system including a polyol as a a system modifier, dispersing in said system particles of an oily core material substantially insoluble in said system, adding sequentially or simultaneously an aqueous solution of urea and an aqueous solution of formaldehyde to said system having said particles of core material dispersed therein, and reacting said urea and formaldehyde in the presence of said polyol to form a condensation product which is insoluble in said system and which forms a solid capsule wall around said particles of core material, wherein said polyol is a diamine of the formula where each R is a hydroxyalkyl group and A is an alkylene bridge.
10. The process of claim 9 wherein said polyol is N,N,N',N'-tetrakis(2-hydroxypropyl) ethylenediamine.
11. The process of claim 9 wherein said process comprises the additional step of adding a polyhydric phenol to said aqueous system.
12. The process of claim 11 wherein said phenol is resorcinol.
13. The process of claim 9 wherein said oily core material is a photosensitive composition.
CA000499652A 1985-03-29 1986-01-15 Amine-formaldehyde microencapsulation process Expired - Lifetime CA1277553C (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US717,930 1985-03-29
US06/717,930 US4594370A (en) 1985-03-29 1985-03-29 Amine-formaldehyde microencapsulation process

Publications (1)

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CA1277553C true CA1277553C (en) 1990-12-11

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CA (1) CA1277553C (en)

Families Citing this family (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6297638A (en) * 1985-10-25 1987-05-07 Kanzaki Paper Mfg Co Ltd Preparation of microcapsule
US5112540A (en) * 1989-12-14 1992-05-12 The Mead Corporation Method of making microcapsules having an improved pre-wall
US5120475A (en) * 1989-12-14 1992-06-09 The Mead Corporation Method for preparing microcapsules having improved pre-walls, and microcapsules and photosensitive materials produced thereby
DE4103966A1 (en) * 1991-02-09 1992-08-13 Basf Ag COLOR IMAGE PREPARATIONS
CN1044336C (en) * 1991-11-18 1999-07-28 碳素种植股份有限公司 Pyrolytic deposition in a fluidized bed
US5281286A (en) * 1992-04-09 1994-01-25 The United States Of America As Represented By The Secretary Of The Army Microcoacervation of propellant ingredients
FR3092502A1 (en) * 2019-02-12 2020-08-14 Européenne D'application Des Cristaux Liquides Formulation of microcapsules with reinforced aminoplast membrane

Family Cites Families (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3516941A (en) * 1966-07-25 1970-06-23 Minnesota Mining & Mfg Microcapsules and process of making
US3755190A (en) * 1971-11-09 1973-08-28 Ncr Capsule manufacture
US4093556A (en) * 1975-07-02 1978-06-06 Loctite Corporation Process for microencapsulation of metallocenes
US4100103A (en) * 1976-12-30 1978-07-11 Ncr Corporation Capsule manufacture
JPS54107881A (en) * 1978-02-14 1979-08-24 Fuji Photo Film Co Ltd Preparation of minute capsule
US4396670A (en) * 1980-04-08 1983-08-02 The Wiggins Teape Group Limited Process for the production of microcapsules
DE3039117A1 (en) * 1980-10-16 1982-05-13 Bayer Ag, 5090 Leverkusen METHOD FOR PRODUCING MICROCAPSULES
DE3044113A1 (en) * 1980-11-24 1982-07-15 Basf Ag, 6700 Ludwigshafen GROCES CONTAINING MICROCAPSULES
JPS57110332A (en) * 1980-12-13 1982-07-09 Kanzaki Paper Mfg Co Ltd Preparation of microcapsule
JPS57147430A (en) * 1981-03-06 1982-09-11 Kureha Chem Ind Co Ltd Preparation of microcapsule

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US4594370A (en) 1986-06-10

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