CN1158138C - Large particle size and high strength oil-containing microcapsules and preparation method thereof - Google Patents

Abstract

The invention relates to a large-diameter high-strength oil-containing microcapsule and a preparation method thereof. It first mixes the bifunctional compound into the inclusion of microcapsules, and then adds it to the aqueous gelatin solution to form the suspension of the inclusion; then adds the aqueous solution of gum arabic to the system, and conducts condensation reaction at 40-60°C and pH 4-6 Form the capsule wall; reduce the temperature to 5-10°C, and form oil-containing microcapsules with a particle size of 0.2-1.5 mm and a wall thickness of 0.01-0.25 mm through surface aggregation and solidification. This method proposes a method combining the aqueous phase precipitation method and the interfacial polymerization reaction method, which is reasonable, simple and easy to operate. It can not only save the material of the capsule wall, but also the capsule wall is relatively tough, which prevents the microcapsules from breaking during subsequent processing, storage and use. Expand the scope of application of microcapsules.

Description

Large particle size and high strength oil-containing microcapsules and preparation method thereof

The present invention relates to the preparation technology of oil-containing microcapsules with large particle size, especially suitable for containing oily liquids or oily liquids containing cosmetics, medicines, magnetic materials, inks, etc., large-particle size, high-strength oil-containing microcapsules and preparation methods thereof .

US Patent No. 5,411,389 discloses a microcapsule containing magnetic powder prepared by using a gelatin/gum acacia system as a microcapsule wall component and adopting an agglomeration method. That is, the light-absorbing magnetic particles and the light-reflecting non-magnetic particles were dissolved in phenolphthalein dibutyl ester at a weight ratio of 4% and 14%, respectively, to obtain a dispersion liquid. Then, add the gum arabic aqueous solution with a weight concentration of 8% to the gelatin aqueous solution with a weight concentration of 8%, and control the pH at 6, so as to obtain an aqueous solution system forming a thin wall of microcapsules. Then, raise the temperature of the system to 50°C, adjust the pH to 4.0, disperse the light-absorbing magnetic particles and light-reflective magnetic particles in phenolphthalein dibutyl ester at a ratio of 1:1, and then add the dispersion to the gelatin/Arabic In the glue solution system, the diameter of the oil droplet is controlled by stirring, and then the temperature of the system is slowly lowered to 10°C, so that the gelatin polymer phase is separated from the aqueous solution, and the gel is precipitated on the surface of the oil droplet. An aqueous solution of glutaraldehyde is then added to crosslink the microcapsule wall material. The diameter of the microcapsule prepared by this method is difficult to reach more than 500 microns, and the low strength of the microcapsule wall is not conducive to subsequent processing and storage.

Japanese Patent Laid-Open No. 4-23581 also discloses a preparation of large-diameter oil-containing microcapsules by utilizing the precipitation and aggregation properties of the gum arabic/gelatin system under certain conditions. The preparation method is similar to the method in the U.S. patent. The prepared microcapsules The strength of the wall material is still low.

During the preparation of microcapsules by the aqueous phase coacervation method, lowering the temperature of the system leads to gelatin precipitation. During the precipitation process, a part of the gelatin is deposited on the oil droplets, and the other part is aggregated with each other, and will precipitate to a certain extent. The ratio of these two fractions of gelatin is controlled both thermodynamically and kinetically. When the particle size of the oil droplet is small (below 100 microns), since the volume of the oil droplet is larger than that of the self-polymer of gelatin, the surface energy of the former is smaller, which is conducive to the formation of gelatin on the oil droplet in thermodynamics. microcapsule wall. However, when the oil droplet particles are very large (more than 500 microns in diameter), the number of oil droplets formed in the water phase is very small. In this case, the number of self-polymers of gelatin is far greater than the number of oil droplets. Kinetically, gelatin tends to form self-aggregates and precipitate, so that the thickness of gelatin coated on the surface of oil droplets is small, so that the strength of the final microcapsule wall is low. On the other hand, microcapsules with larger diameters have larger radii of curvature, resulting in microcapsules that are structurally more fragile. Therefore, it is impossible to prepare microcapsules with larger particle size and higher strength by aqueous precipitation method.

The purpose of the present invention is to overcome the defects of the prior art, and provide a large particle size, high strength oil-containing microcapsule and a preparation method thereof by combining the aqueous phase precipitation method and the interfacial polymerization reaction method.

The purpose of the present invention can be achieved through the following measures:

A method for preparing large particle size, high-strength oil-containing microcapsules, comprising the following steps:

Step 1: Prepare materials

Prepare materials according to the following components and their weight percentages based on the dry weight of pure materials:

Components % by weight

Gelatin 4～7%

Gum Arabic 4～7%

Oil 5～10%

Bifunctional compound 0.5～1.5%

Additives 0～12%

Glutaraldehyde 0.5%

Water 70～80%

Step 2: Preparation of inclusions, aqueous gelatin solution, and aqueous gum arabic solution

(1) Mix oils and additives evenly to prepare microcapsule inclusions, and mix bifunctional compounds into the inclusions;

(2) preparing respectively a gelatin aqueous solution with a weight concentration of 5 to 15% and an aqueous gum arabic solution with a weight concentration of 5 to 15%, and adjusting their pH values to weakly acidic;

Step 3: Combining aqueous phase precipitation and interfacial polymerization to form microcapsules

(1) Add the mixture of step 2(1) into the aqueous gelatin solution of step 2(2), stir to suspend the inclusion drop in the gelatin aqueous solution, and control the size of the inclusion drop by controlling the stirring speed;

(2) Add the gum arabic aqueous solution equal in weight to the gelatin aqueous solution into the system; then raise the temperature to 40-60°C, and reduce the pH value of the system to 4.0-6.0, so that the bifunctional substances mixed in the inclusions and The gelatin dissolved in water and the hydroxyl groups in gum arabic undergo condensation reactions to form the initial microcapsule wall; then slowly lower the temperature to 5-10°C to make the gelatin dissolved in water and gum arabic in the formed microcapsule wall The surface of the capsule wall aggregates to form microcapsules with gelatin/gum arabic/bifunctional compound as the wall material;

Step 4: Curing of Microcapsule Walls

The weight concentration is that 15～30% glutaraldehyde aqueous solution is added in the above-mentioned system, to further cross-link the microcapsule wall material, through the reaction time of 10～25 minutes, the thin polymer wall wrapped in the inclusion is just solidified into a relatively Tough and transparent shell; filter the prepared microcapsules with stainless steel mesh and dry to obtain oil-containing microcapsules with a particle size of 0.2mm-1.5mm and a wall thickness of 0.01mm-0.25mm.

The bifunctional compound is selected from substances containing bifunctional groups that can react with the gelatin/gum arabic system, such as dibasic acid chlorides, diamines, or diisocyanates.

Additives are selected from substances that can make the microcapsules have specific functions, such as cosmetics, medicines, magnetic materials, inks, and the like.

Compared with the prior art, the present invention has the following outstanding advantages:

1. Combining the aqueous phase precipitation method and the interfacial polymerization reaction method for the first time, a new large particle size, high strength oil-containing microcapsule and its preparation method are proposed. In this method, the interface reaction is used to adsorb a part of gelatin and gum arabic on the surface of oil droplets to reduce the concentration of gelatin/gum arabic in the water phase, thereby inhibiting the self-polymerization of gelatin and gum arabic, and successfully preparing oil-containing microparticles with a particle size of more than 1mm. capsule. When the particle size of the microcapsule is large and the dosage of the capsule wall material is constant, more microcapsule inclusions can be accommodated, thereby saving the capsule wall material; in addition, the scope of application is expanded, especially in many special occasions, such as magnetic display materials. Microcapsules with large particle size are used.

2. The addition of bifunctional substances plays the role of cross-linking gelatin and gum arabic, thereby greatly improving the strength of the microcapsule wall material. When the strength of the microcapsule wall material is improved, on the one hand, the thickness of the capsule wall can be reduced, thereby further saving the capsule wall material; on the other hand, the microcapsule can be prevented from breaking during subsequent processing, storage and use.

The present invention is described in further detail by the following examples:

Example 1

Components % by weight based on dry weight of pure material

Gelatin 5%

Gum Arabic 5%

Dibutyl phthalate 10%

phthaloyl chloride 0.5%

Glutaraldehyde 0.5%

Water 79%

According to the above ratio, dibutyl phthalate and phthaloyl chloride are uniformly mixed to prepare microcapsule inclusions. The gelatin aqueous solution and the gum arabic aqueous solution were respectively prepared into aqueous solutions with a weight concentration of 11%, and their pH values were adjusted to 6.

Add the prepared microcapsule inclusions, that is, the mixture of dibutyl phthalate and phthaloyl chloride, into the aqueous gelatin solution, and stir to obtain O/W latex. The inclusions are suspended in the aqueous gelatin solution, and stirred by controlling The velocity controls the size of the inclusion droplet. Then the prepared aqueous solution of gum arabic was added into the system, and the temperature was raised to 40° C., while the pH value of the system was lowered to 4.0. Add hot water at 40°C four times that of the gelatin aqueous solution into the latex, stir, and slowly lower the temperature to 10°C to form a thin polymer wall on the surface of the inclusion.

Glutaraldehyde was dissolved in the remaining water and added to the above system to further crosslink the microcapsule wall material. After a reaction time of 25 minutes, the thin polymer walls surrounding the inclusions solidified into a relatively hard, transparent shell. Filter the prepared microcapsules with a stainless steel mesh and dry to obtain oil-containing microcapsules with a particle diameter of 1.5 mm and a wall thickness of 0.05 mm.

Example 2

Components % by weight based on dry weight of pure material

Gelatin 7%

Gum Arabic 7%

Liquid Paraffin 5%

Toluene diisocyanate 1.0%

Vaseline 5%

Sorbitan Sesquioleate 1%

Spices 0.01%

Glutaraldehyde 0.5%

Water 73.4%

According to the above proportion, liquid paraffin, vaseline, sorbitan sesquioleate, spices and toluene diisocyanate are uniformly mixed to prepare microcapsule inclusions. The gelatin aqueous solution and the gum arabic aqueous solution were respectively prepared into aqueous solutions with a weight concentration of 15%, and their pH was adjusted to 6.

The prepared microcapsule inclusions are added to the gelatin aqueous solution, stirred to obtain O/W type latex, the inclusion drop is suspended in the gelatin aqueous solution, and the size of the inclusion drop is controlled by controlling the stirring speed. Then the prepared aqueous solution of gum arabic was added into the system, and the temperature was raised to 50° C., while the pH value of the system was lowered to 4.5. Then add 50°C hot water four times that of the gelatin aqueous solution into the latex, stir, and slowly lower the temperature to 10°C to form a thin polymer wall on the surface of the inclusion.

Glutaraldehyde was dissolved in the remaining water and added to the above system to further crosslink the microcapsule wall material. After a reaction time of 10 minutes, the thin polymer walls surrounding the inclusions solidified into a relatively hard, transparent shell. Filter the prepared microcapsules with a stainless steel mesh and dry to obtain cosmetic-containing microcapsules with a particle size of 0.3 mm and a wall thickness of 0.01 mm.

Example 3

Components % by weight based on dry weight of pure material

Gelatin 4%

Gum Arabic 4%

Dioctyl phthalate 10%

ethylenediamine 1.5%

Iron Tetroxide Powder 7%

Glutaraldehyde 0.5%

Water 73%

According to the above-mentioned proportion, dioctyl phthalate, ferric iron tetroxide powder and ethylenediamine are uniformly mixed to prepare microcapsule inclusions. The gelatin aqueous solution and the gum arabic aqueous solution were respectively prepared into aqueous solutions with a weight concentration of 11%, and their pH values were adjusted to 6.5.

The prepared microcapsule inclusions are added to the gelatin aqueous solution and stirred to obtain O/W latex, the inclusions are suspended in the gelatin aqueous solution, and the size of the inclusions is controlled by controlling the stirring speed. Then the prepared aqueous solution of gum arabic was added into the system, and the temperature was raised to 60° C., while the pH value of the system was lowered to 5.0. Then add 60°C hot water four times that of the gelatin aqueous solution into the latex, stir, and slowly lower the temperature to 10°C to form a thin polymer wall on the surface of the inclusion.

Glutaraldehyde was dissolved in the remaining water and added to the above system to further crosslink the microcapsule wall material. After a reaction time of 10 minutes, the thin polymer walls surrounding the inclusions solidified into a relatively hard, transparent shell. Filter the prepared microcapsules with a stainless steel mesh and dry to obtain magnetic microcapsules with a particle diameter of 1.0 mm and a wall thickness of 0.25 mm.

Claims (3)

1, a kind of preparation method of large particle size high strength oil-containing microcapsules, it comprises the following steps: Step 1: Prepare materials Prepare materials according to the following components and their weight percentages based on the dry weight of pure materials: Components % by weight Gelatin 4～7% Gum Arabic 4～7% Oil 5～10% Bifunctional compound 0.5～1.5% Additives 0～12% Glutaraldehyde 0.5% Water 70～80% Step 2: Preparation of inclusions, aqueous gelatin solution, and aqueous gum arabic solution (1) Mix oils and additives evenly to prepare microcapsule inclusions, and mix bifunctional compounds into the inclusions; (2) preparing respectively a gelatin aqueous solution with a weight concentration of 5 to 15% and an aqueous gum arabic solution with a weight concentration of 5 to 15%, and adjusting their pH to weak acidity; Step 3: Combining aqueous phase precipitation and interfacial polymerization to form microcapsules (1) Add the mixture of step 2(1) into the aqueous gelatin solution of step 2(2), stir to suspend the inclusion drop in the gelatin aqueous solution, and control the size of the inclusion drop by controlling the stirring speed; (2) Add the gum arabic aqueous solution equal in weight to the gelatin aqueous solution into the system; then raise the temperature to 40-60°C, and reduce the pH value of the system to 4.0-6.0, so that the bifunctional substances mixed in the inclusions and The gelatin dissolved in water and the hydroxyl groups in gum arabic undergo condensation reactions to form the initial microcapsule wall; then slowly lower the temperature to 5-10°C to make the gelatin dissolved in water and gum arabic in the formed microcapsule wall The surface of the capsule wall aggregates to form microcapsules with gelatin/gum arabic/bifunctional compound as the wall material; Step 4: Curing of Microcapsule Walls The weight concentration is that 15～30% glutaraldehyde aqueous solution is added in the above-mentioned system, to further cross-link the microcapsule wall material, through the reaction time of 10～25 minutes, the thin polymer wall wrapped in the inclusion is just solidified into a relatively Tough and transparent shell; filter the prepared microcapsules with stainless steel mesh and dry to obtain oil-containing microcapsules with a particle size of 0.2mm-1.5mm and a wall thickness of 0.01mm-0.25mm. 2. The method for preparing oil-containing microcapsules with large particle size and high strength according to claim 1, characterized in that the bifunctional compound is: a dibasic acid chloride containing a bifunctional group capable of reacting with the gelatin/gum arabic system Or diamines or diisocyanates. 3. A method for preparing oil-containing microcapsules with large particle size and high strength according to claim 1, characterized in that the additives are cosmetics, medicines, magnetic materials or inks.