DE2137574C3 - Process for the production of oil-containing microcapsules - Google Patents

Description

The invention relates to a process for the preparation of oil-containing microcapsules by emulsifying or suspending the Kernniateriais in an aqueous solution one hydrophilic gellable polymer, depositing a coacervate phase in the Eimul- ^a 5 tion or suspension gelation of the deposited on the core particles coacervate by Cooling and hardening of the gelled capsule walls.

Processes for making microcapsules by coacervation are described, for example, in U.S. Patent 3 <J Writings 28 00 457 and 28 00 458 described.

Such processes, which rely on the separation of a coacervate phase, are for microencapsulation of liquid droplets which may contain a material dissolved or dispersed therein. However, it is difficult to control the various conditions therefor. The formation of the coacervate is determined by the colloid concentration, the salt concentration, the pH of the system, the ratio of the colloid to the material to be encapsulated, the * ° Affects agitation conditions of the system, temperature and similar factors.

In order to prevent aggregation of the capsules due to an increase in viscosity in such processes System to prevent if the pH value drops rapidly * 5 If the hardening of the coacervate is changed, the colloid concentration must be limited to 2.5%. A large difference in slurry viscosity is obtained since, for example, the non-targeting Ge-Jatine deposited by the encapsulating liquid droplets remains in the system.

In French patent 15 42881 is a Process for the production of microcapsules described, wherein a step of the separation of a film-forming polymeric complex from the solution of a plurality of polymeric materials that form complexes are capable of being carried out with each other.

However, even after this method of operation, the difficulties described above cannot yet can be satisfactorily eliminated.

The object of the invention is to ship a method for the production of oil-containing microcapsules with thick walls and low porosity. In particular The invention aims to develop a method in which a high colloid concentration is used chins are assumed

This object is achieved according to the invention by a method for producing

60 oil-containing microcapsules by emulsifying or suspending the core material in an aqueous solution of a hydrophilic gellable polymer, depositing a coacervate phase in the emulsion or suspension, gelling the coacervate phase deposited on the core particles by cooling and hardening the gelled cap walls, which is characterized in that a phenol or phenolic resin is added between the gelling step and the hardening step.

In particular, the following advantages are achieved by the method according to the invention:

a) As allows the formation of the capsules using a higher colloid concentration large amounts of capsules can be formed and, as a result, the manufacturing cost becomes low decreased; in addition, the amount of the coating mass to be evaporated at Applying the capsule solution to a carrier material or reduces the amount of solvent to be evaporated decreased in the concentration of the capsule solution. This simplifies the devices for evaporation.

b) The liquid to be encapsulated is effective to the amount of the colloid.

c) All the steps in the above process are carried out continuously, as there is no increase the viscosity is caused and the level of hardening of the system is not the rate-limiting one Level becomes while the load on the stirrer is reduced.

The phenols used in the context of the invention include substituted phenols, polyhydric phenols, Phenol carboxylic acids, nitrophenols, biphenols. They can usually be found as a solution in water or alcohols be used.

The substituted phenols include o-cresol, m-cresol, p-cresol, o-ethylphtnol, p-tert.-butylphenol, p-Nonylphenol, p-Dodecylphenol, p-Octylphenol, p-fluorophenol, p-chlorophenol, p-bromophenol, m-chlorophenol, p-Cyclohexylphenol, o-Phenylphenol, p-Phenylphenol, o- (o-chlorophenyl) -phenol, p- (p-bromophenylj-phenol, o- (2-biphenylyl) -phenol, a-phenyi-ocresol, 2,4-xylenol, 3,4-xylenol, 2-allyl-p-cresol, 2,4-dichlorophenol, 2,5-dichlorophenol, 4-chloro-m-creso !, 2-chloro-4-phenylphenol, 2,3,5-trimethylphenol, 2,3,5, 6-tetramethylphenol, «i-naphthol, / I-naphthol.

Examples of polyhydric phenols include resorcinol, catechin, hydroquinone, pyrogallol, Fluoroglycine, 1,2-dihydroxy-4-methylbenzene, 1,3-dihydroxy-5-methylbenzene, 3,4-dihydroxy-1-methylbenzene, 3,5-dihydroxy-1-methylbenzene, 2,4-dihydroxy ethylbenzene, tert-butylhydroxyquinori, 1,3-naphthalenediol, 1,4-naphthalenediol, 1,5-naphthtilinediol, 1,6-naphthalenediol, 1,7-naphthalenediol, 4-phenylpyrocatechol, 4-chlororesorcinol, Phenylhydroquinine, 4,6-dichlororesorcinol, Tetrachlorohydroquinone.

Examples of phenol carboxylic acids are given m-oxybenzoic acid, p-oxybenzoic acid, protocatechuic acid, a-resorcylic acid, / Ϊ-resorcylic acid, orsellic acid, Caffeic acid, umbellic acid, bile acid. Examples of nitrophenols are p-nitrophenol, m-nitrophenol, called o-nitrophenol.

Examples of biphenols include; n Biphenol, Bicresol, Diethylbiphenol, Dipropylbiphenol, Öiallylbiphenol, Dihalogenbiphenol, Biphenyltetrol, Methylendiphenol, Methylenebis (alkylphenol), methylenebis (benzylphenol),

Methylenebis (phenylphenol), methylenebis (hafogenphenolj.

Examples of compounds of the biphenol type are ο, ο'-biphenol, m.m'-biphenol, p, p'-biphenol 4 4'-Bi o-cresol, 4,4'-Bi-m-cresoI, 6,6'-o-cresel, 2,2'-diethyl- s ρ, ρ'-biphenol, 2,2'-diallyl-p, p'-biphenoI, 3,3 ', 5 5'-biphenyltetrol, 4,4'-methylenediphenol, 2,4'-methylenediphenol, 2,2'-methylenediphenol, 4,4'-isopropylidenediphenol, 4,4'-Cyclopentylidenephenol, 4,4'-CycIohexyIidendiphenol, Methyiendiresorchi, 4,4'-MethyIen-di-ocresol, 4,4'-methylenebis (2-chlorophenol), 4,4'-methylenebis (2,5-dichlorophenol), 4,4'-thiodiphenol. The above phenolic monomers can be used as the sodium or potassium salt.

Typical examples of the phenolic resins used in the context of the invention include phenol aldehyde condensates, which are generally referred to as resol type or novolak type resins.

Water-soluble phenolic resins are for the invention This method is more suitable, but so-called alcohol-soluble novolak types can also be used after they have been dissolved in a solvent compatible with water.

The following measures are used to carry out the method according to the invention, namely a ₅

1. Suspending a hydrophobic fine powder or emulsifying a hydrophobic liquid in the aqueous solution of at least one kind of a hydrophilic gellable polymer which is used for Wall formation is used (dispersion or emulsification stage),

2. Dilute the suspension or emulsion according to step 1. with water and then add salt or / and pH adjustment of the same. If desired, an aqueous solution of a high molecular colloids are added to this (coacervation stage),

3. Cooling of the formed coacervate for gelation (cooling step),

4. Addition of phenol or phenolic resin at a temperature above 8 C,

5. addition of a hardening agent to the system,

6. Addition of an anti-shock agent at a temperature lower than the gelling point of Gelatin, under shock the phenomenon is to be understood that the viscosity of the system rapidly at a pH close to 6 to 9 in the case of performing the pre-hardening of the coacervate capsule liquid, which contains gelatin, increases and with shock preventive means the solution for the prevention of shock,

7. Adjustment of the pH value of the system to the alkaline side (steps 5, 6 and 7 above: Pre-hardening treatment), and

8. Increasing the temperature of the system (hardening stage).

Examples of hydrophilic gellable polymers include gelatin, casein, alginate, gum arabic, Carrageenan, maleic acid-styrene copolymers, maleic acid-methyl vinyl ether copolymers, maleic acid-ethylene copolymers. In the method of the present invention, gelatin must be used as one of the hydrophilic colloids will.

In addition to hydrophobic solid particles, natural and synthetic are used as core materials for the capsules oils into consideration.

Typical examples of hardening agents include formaldehyde, acetaldehyde, glyoxal, glutaraldehyde, Chrome alum.

Shock prevention agents are, for example, compounds with anionic functional groups, such as cellulose derivatives, such as carboxymethyl cellulose, carboxyethyl cellulose, sulfated cellulose, phosphorized Cellulose, carboxymethyl hydroxyethyl cellulose; Starch derivatives such as carboxymethyl starch, sulfated Starch, phosphorized starch; D-gelactonic acids such as pectin, pectic acid; Vinylbenzenesulfonic acid or sulfonate copolymers, such as vinylbenzenesulfonate-acryloyl-morpholine copolymers, Vinylbenzenesulfonate-acrylamide copolymers, vinylbenzenesulfonate-vinylpyrrolidone copolymers and acrylic acid or acrylic acid salt copolymers such as acrylic acid-acryloylmorpholine copolymers, Acrylic acid-vinylpyrrolidone copolymers. Such shock prevention means are in the German Offenlegungsschrift 19 39 624 described.

The amount of the phenol compound is ^l / i, oo to _^3/4 parts by weight, preferably V100 V to ₂ parts by weight based on 1 part by weight of gelatin used to form the wall.

The viscosity variation of the previously known coacervation processes was identical to that in Method according to the invention compared using the Phenolverbifldung.

A system (coacervation pH = 4.5) with 11 parts by weight of a colloid (6 parts gelatin and 5 parts gum arabic) used in 210 parts by weight of water. When practicing the method according to the invention Resorcinol was added at a temperature of 30 ° C.

USA.-

Patent addition of

28 00 457 resorcinol

Secluded crowd
of gelatin

Viscosity at 10 C

Maximum viscosity
during instillation
of alkali

76 ° _o 85%

84 cp 42 cp

6700 cp. 2500 cp

The addition of resorcinol results in the method for producing capsules in combination the water dilution with the pH adjustment according to the USA. Patent 28 00 457 a An increase in the deposited amount of gelatin and microcapsules with thick walls and result with lower porosity. Furthermore, the viscosity is lower at 10 C and during the pH adjustment humbled than half.

With the aid of the method according to the invention, color formers for pressure-sensitive copier papers can be produced. Perfumes, Adhesives, catalysts, chemicals, or drugs can be encapsulated.

The following examples serve to further illustrate the invention.

In the examples, parts are based on weight and the viscosity is given in Centipoisc (cp), the was determined by means of a B-type rotary viscometer.

5 6

Example 1 Example 3

In 20 parts of warm water at 35 ° C., the same procedure as in Example 2 was repeated as parts of acid-treated gelatin with an isoelectrode, but 0.5 part of bile acid was dissolved by a point of 8.2. Then 35 parts of 5 0.3 parts of 4,4'-bis (4-oxyphenyl) sulfone were replaced and added to lemon oil and emulsified, so that an emul site of 5 parts of methanol 4 parts of methanol version of the oil-in-water Type was obtained. When it turns. The viscosity at 10 C was 27 cp and when the oil droplets were 20 to 25 μ, the stirring pH was 8 it was 34 cp.
interrupted and 6 parts of gum arabic dissolved in

180 parts of warm water at 35 C became an "e-" Example 4

poured, whereupon the pH value was then increased to 4.2 by _{pouring in 2} o parts of warm water at 35.degree

drops of 10% hydrochloric acid with stirring einge- _{6 Tei} | _it äurebehandelte gelatin with an isoelectronic

was steep. Dissolved the tric point of 8.2 with cooling from outside the vessel,

was cooled with stirring to remove the deposited. Then 35 parts of liquid paraffin were used

To gel colloid walls. When the temperature of 15 produces an oil-in-water type emulsion

System was 25 C during the cooling stage, were emulsified. When the oil droplets were 20 to 25 μ,

10 parts of a 5 _{was> u} züge- aqueous Catechinlösung interrupted _stirring and 3 parts of rubber

give, and, when the temperature was 10 C, were _ara bicum, dissolved in 160 parts of warm water from

20 parts of a 10% sodium sulfate cellulose (Ver 350 _{c were} poured in, whereupon the pH value

degree of esterification 0.74, viscosity in 2% aqueous 2O _{42 by dropping in} 10% hydrochloric acid below

Added 64 cp), and further _R ü was adjusted _NREN - solution at 25 C. The vessel was from the outside

3.0 parts of 37% formaldehyde were poured in _{with stirring to} gel the deposited

(Viscosity at 10 C = 20 cp). Colloid walls were then cooled. When the temperature of the

the pH was increased to 9.5 by dropping 10% _system s 22 C during the cooling stage

Set sodium hydroxide solution and the viscosity was 36 cp »5 _{for the system} 5 _{parts e} one made of resorcinol and formal

at pH 8.0. _{deh i.e. erge} phenolic resin (60% solids contents introduced

The solution was then heated to 45 _° C. and a good deal added. When the temperature of the system

heat-resistant single-core capsules, which contained lemon oil | 0'C, 20 parts of a 10% sulfate

held, received. Cdlulose sodium salt (degree of esterification 0.74,

³ ° viscosity at 25 C in 2% aqueous solution 64 cp)

Example 2 added, continued and refrigerated when the system

In 30 parts of warm water at 35 C were 8 C, 3.0 parts were 37% formaldehyde

6 parts of acid-treated gelatin with an isoelek- poured in. The viscosity was 18 cp ^{at 10 1 C.}

Tric point 8.2, 5 parts of gum arabic and 0.2 Then the pH was adjusted to 9.5 by dropping

Parts of polyacrylic acid dissolved. ³⁵ of 10% sodium hydroxide solution set. The viscosity

Then 20 parts of an epoxy resin was emulsified, pH 8.0 was 26 cp and the solution was dissolved

until the size of the emulsion droplets was 50 μ. 45 C heated and good heat resistant single core

Then, 180 parts of warm water was obtained from capsules containing liquid paraffin.
35 C is added and the pH adjusted to 4.3 by pouring 50 ° _o acetic acid. Then ⁴ ° was comparative example 4a
cooled from outside the vessel with stirring. _{The same procedure as in Example} 4 _{was as} follows. When the temperature of the system was 12 C wur- _{Derho, but no phenol resin was} used. The 0.5 part of bile acid dissolved in 5 terfen of methanol, the _{viscosity of the} capsule solution obtained was 67 cp and, when the temperature was 8 C, it was _{οχ and at} " _g " _{during the change of} the 25 parts of a 5% , gen aqueous Pekt.nsaurelosung _{H. It was worth} 643 cp.
and then 3.5 parts of 25% glyoxal to ^v & ν
given. Example 5

The viscosity at 8 ° C. was 35 cp. Furthermore, _{25 teaspoons of warm water of 3rc were made}

the pH was reduced to 9 5 by adding 10% .ger . _{ acid-treated gelatin with an isoelectronic

Caustic soda set. The viscosity is at pH 8.0. _{point of 7 g 4 parts gum arabic and}

carried 39 cp. It was then heated to 40 C to dissolve capsules, j styrene-maleic copolymers,

containing the epoxy resin. The obtained _were \ _{Q T} ue le monöl emulgieVt. When

nen capsules were single-core capsules and could _{dj fhd} oil-in-water emulsion 20 to 25 μ

be stored without breakage, even after 10 hours _Dia ^P _{had eater), 170 parts of warm Watl} £

rv ΐ. ν t T .Ti ^. of 35 "C. The pH was then poured up to

The microcapsules were used as adhesive capsules with sulfuric acid.

de. The dry, produced by spray drying, the vessel is cooled from the outside in order to

The nete powder was dispersed in a polyamide solution _{γ If} ⁸ _{the temperature} ^ß , ₂ C

and could be used as a pressure-sensitive adhesive from the _6q »phenolic resin (6O ⁰ J ^ solid

Fluss.gke.ts.yp are stored. _haU) ^ _{then 5 parts} , _{e 20} y ^ _v glutaraldehyde

...... . added and cooled ^{to 8 0 C.}

Comparative Example 2a 2 parts of a 10% carb-The same procedure as in Example 2 was added to oxymethylhydroxyethyl cellulose and the pH was repeated, but without adding the solution from bile 6s value to 9.2 by dropping 10% sodium acid in Methanol. The viscosity at 10 C during alkali set and the contents at 40 ⁰ C for the preparation of the capsules was 70 cp, and heated at obtain capsules with hardened walls pH 8.0 it was 121 cp. would.

The viscosity at 8 "C during the manufacture of the capsules was 38 cp and the viscosity at pH 8.0 was 67 cp.

Example 6

6 parts of acid-treated gelatin, 5 parts of gum arabic and 0.2 parts of polyacrylic acid were used in 30 Parts of polysulfide resin emulsified so that emulsion droplets with 50 μ size were obtained. After addition from 175 parts of warm water at 35 C, 50% acetic acid was used to adjust the pH 4.3 poured in. It was then cooled from outside the vessel with stirring and when the Temperature was 25 C, were 6 parts of a phenol-formaldehyde resin added. When the temperature of the system was 8 ° C, there became 30 parts of a copolymer of potassium vinylbenzenesulfonate with mor-

pholin (mole number of Kaliumvinylbenzolsulfonats 76.5%, intrinsic viscosity (determined in in-NaNO ₃ at 30C = added 0.421), and then 3 parts poured in 37% formaldehyde, to which 10 _"u strength sodium hydroxide solution dropwise on to adjust the pH-value 9.5 was added, and the viscosity at pH 8.0 was 54 cp. By heating the system to 40 ° C., capsules containing the thiokol resin were obtained.

ίο The capsules obtained were effective as Use capsules for pressure sensitive adhesives.

Comparative example 6a

The procedure was as in Example 6, but no phenolic resin was used. The viscosity at pH 8.1 was 136 cp.

Claims (1)

Patent claim: Process for the production of oil-containing microcapsules by emulsifying »resp. Suspending the Nuclear material in a v.issrigea solution of a hydrophilic gellable polymers, separation of a coacervate phase in the emulsion or suspension, Gelation of the coacervate phase deposited on the core particles by cooling and Hardener, the gelled capsule walls, thereby characterized that between the vulture stage and a phenol or phenolic resin is added to the curing step. 15th