JPS60175538A - Preparation of microcapsule - Google Patents

Abstract

PURPOSE:To simply microencapsulate a substance solid at an ambient temp., by a method wherein a core substance solid at an ambient temp. is ground at a temp. lower than said ambient temp. and the ground core substance is mixed with a wall substance under stirring at the grinding temp. to coat the core substance with said wall substance. CONSTITUTION:A substance solid at an ambient temp. (e.g., camphor) is used as a core substance and this core substance is ground at a temp. lower than the ambient temp. and, subsequently, the ground core substance is mixed with a wall substance (e.g., stearyl alcohol) under stirring at the grinding temp. to coat the core substance with said wall substance. That is, the substance solid at an ambient temp., especially, a substance easily generating chemical or physical change at an ambient temp. can be simply and safely microencapsulated in high yield.

Description

[Detailed Description of the Invention] a. Technical field The present invention uses wJ quality, which is in a solid state at room temperature, as a core material,
This concerns a method of microencapsulating this.

The present invention relates to a method for producing microcapsules that is particularly effective when the core substance is a substance that easily undergoes chemical or physical changes at room temperature.

b. Prior art and its problems As is well known, microcapsules are widely used in pressure-sensitive copying paper, medicines, agricultural chemicals, fragrances, and the like.

Typical conventional microcapsule manufacturing methods include coacervation method, interfacial polymerization method, in-situ polymerization method, submerged drying method, melt dispersion cooling method, orifice method, spray drying method, and air suspension ridge method. , inorganic wall microencapsulation method, etc.

However, this manufacturing method is difficult to apply when microcapsulating substances that are solid at room temperature and are susceptible to chemical or physical changes at room temperature (hereinafter referred to as reactive solid substances). Met. That is, in the above conventional method, Iy7. In the process of microencapsulation, the surface value of a reactive solid substance increases as it becomes finer, making it easier for the above changes to occur, and chemical or physical changes occur frequently before the surface of the fine particles is covered with a wall material. However, the desired microcapsules cannot be obtained. In addition, even for substances (such as aluminum) that form a very thin film of reaction products only on the surface due to chemical reactions in a bulky solid state at room temperature, when the specific surface area is increased by pulverization, the reaction in the resulting fine powder This may result in an undesirable increase in the proportion of the product.

C0 Purpose of the Invention The present invention has been made in view of the above circumstances, and it is possible to easily microcapsulate substances that are solid at room temperature, especially substances that easily undergo chemical or physical changes at room temperature, in a high yield and safely. The purpose of the present invention is to provide a method for producing microcapsules that can be used to produce microcapsules.

d1 Structure of the invention The present invention will be explained in detail below.

In the method for producing microcapsules of the present invention, when a substance that is solid at room temperature is microencapsulated as a core material, the core material is pulverized at a temperature lower than room temperature, and then the core material is mixed with a wall material at this temperature. 4. Stirring to coat the core** with the wall material.
9Itk, and in the above manufacturing method, the core substance is a substance that undergoes a chemical or physical change at room temperature, and the pulverization of the core substance and mixing and stirring with the wall substance are
It is characterized in that it is carried out at a temperature at which no chemical or physical change of the core substance occurs or at a temperature at which it can be considered that substantially no chemical change or physical change occurs.

First, the core material used in the manufacturing method of this invention is as follows:
Odorous substances such as amino acids, deliquescent substances such as potassium hydroxide, magnesium chloride, calcium chloride, sodium hydroxide, sublimable substances such as naphthalene and camphor, etc., are subject to chemical changes such as oxidation reactions and sublimation at room temperature. Various substances that easily undergo physical changes can be mentioned. However, it is necessary that the above-mentioned change is suppressed or the rate of change is sufficiently slowed to be substantially suppressed at an appropriate low temperature below room temperature.

The wall material covering the core material is determined depending on the relationship with the core material, but the following materials are generally used. First, lauri 7, myristic acid,
Higher fatty acids such as stearic acid and oleic acid, higher alcohols such as lauryl alcohol, palmityl alcohol, and stearyl alcohol, higher fats such as palmitic acid amide, stearic acid amide, and oleic acid amide1
Higher fatty acid esters such as amide, glycerin fatty acid ester, higher fatty acid gold salts such as aluminum stearate, zinc stearate, calcium stearate, lead oleate, zinc oleate, copper palmitate, carnauba wax, paraffin wax, Natural and petroleum waxes such as beeswax, wood wax, tallow wax, caldera wax, polyethylene wax, and oxidized paraffin wax; natural and synthetic resins such as rosin fat and terpene resin; solid fat such as beef tallow; gelatin jelly; Examples include foods such as butter and melt-type cheese, and easily meltable metals such as Wood alloys and Newtonian alloys. These wall materials are solid at around room temperature, and as will be described later, when mixed with the core material at a low temperature, they become finer than the core material at that temperature, and the particles generated during the mixing and stirring. It is necessary that the viscosity of the wall material be lower than the viscosity of the core material at the temperature of local heat generated on the particle surface due to friction between particles. It should be noted that these viscosity comparisons are made at temperatures near the melting or softening point of the wall material, and the wall material in the method of the present invention has a melting or softening point of about 200° C. or less in relation to the local heat generated. Preferably, one dose of the substance is used.

Furthermore, when selecting a wall material to be combined with the core material, it is necessary to select a material that does not cause chemical changes at the interface when brought into contact with the core material at room temperature.

Next, microencapsulation will be explained.

First, the core substance is cooled using cold energy such as the forehead spirit element,
Powder it in this state. The temperature at this time is the property of the core material)
Depending on the ML (chemical or physical property yi), the temperature or desired ambient atmosphere is such that no chemical or physical change in the core substance occurs, or the rate of change is sufficiently slow that it can be considered that no change occurs substantially. It is necessary.

Next, while maintaining this powder at a low temperature to prevent chemical or physical changes, the above-mentioned wall material is added and mixed and stirred to form microcapsules. For this mixing and stirring, it is preferable to use a Cutter high-speed stirrer equipped with a liquefied nitrogen cooling jacket, and the stirring conditions are a stirring speed of 5,000 to 30.00 rpm, and a stirring time of several seconds to 1000 rpm.
It's a minute. In particular, when using this type of (・6: God), the above-mentioned freezing and pulverization can also be performed within this device, which is advantageous in terms of the process.In addition, ball mills, stirrers with cutters, attritors, etc. can also be used for mixing and stirring. The temperature during stirring is the same as the temperature during freeze-grinding, and in order to prevent temperature rise due to frictional heat, the stirrer must be continuously cooled by passing a coolant such as liquefied nitrogen. The mixing ratio of the core material powder and the wall material also depends on the shape of the core material powder; if the powder is spherical, a small amount of wall material is required, but usually 100 parts by weight of the core material powder is used. In addition, the particle size of the microcapsules obtained is determined by the particle size of the core material powder and the film thickness of the wall material. 114 seconds can be set arbitrarily depending on the mixing ratio of the material and wall material and the mixing and stirring conditions, and the average particle size is 1 to 1500 μm.
microcapsules can be obtained satisfactorily. During this mixing and stirring operation, the powder of the wall material is more likely to be atomized than the core material at the temperature during stirring, so when the core material and wall material collide, the surface of the core material After the atomized wall material physically adheres to the surface, frictional heat is generated locally on the collision surface of the two, which causes the wall material to flow and become heated due to the viscosity of the wall material being lower than that of the core material. It is smeared onto the surface of the material powder, thereby covering the core material powder with the wall material.

In the microcapsules V thus obtained, the core material powder is completely covered with the wall material, and the powder remains smooth and fluid even at room temperature.

In addition, the microcapsules obtained by the above steps are
Since the capsule may have air permeability to the core material, if necessary, to achieve more complete encapsulation, the surface of the microcapsule may be coated with a polymer using a vapor phase method, etc. What is necessary is to perform a process such as dissolving and re-solidifying the wall material of the microcapsules to achieve densification.

Also, the flow of microcapsules obtained! 14 If you want to further improve the JJ properties or to make the wall material more completely coated, use the following average particle size of about 10 during the above mixing and stirring process.
A small amount of fine powder of 0 μm or less can also be added. Fine powders include silica fine powder, various bentonites, aluminum oxide, carbon black, calcium carbonate, talc,
Examples include kaolin% titanium oxide, ceramic powder, phytic acid and its gold salt, fine powder of synthetic resin such as polyethylene, nylon, methacrylate, starch, and fine powder obtained by surface treatment of these powders. The amount of this fine powder added is 0.5 to 100 parts by weight of the core material powder.
5 parts is enough.

According to this method of manufacturing microcapsules.

Freeze and crush the core material and turn it into powder, and add this to the wall? Since the material is added and mixed and stirred at low temperature, chemical or physical changes in the core material during production are dramatically suppressed.
There is no loss of core material, microcapsules can be produced at high yields, the process is simple and can be produced in a short time, and the production equipment requires only a stirrer, so the production cost is extremely low. . Furthermore, since all processes are carried out at low temperatures that can suppress changes in the core material, degeneration and alteration of the wall material as well as the core material can be suppressed. Furthermore, compared to conventional methods that use water or organic solvents, there is no need for a drying process or wastewater treatment, and the work is highly safe. Since the particle size of the microcapsules can be arbitrarily and easily adjusted, microcapsules with a particle size suitable for the purpose can be easily prepared.

Furthermore, as described above, the method of the present invention is highly effective for core substances that are highly active at room temperature, but is also effective when an inactive substance is used as the core substance.

That is, by freezing and pulverizing the core material at low temperatures, fine pulverization becomes easy and the total surface area of the core material can be increased, resulting in good microcapsules.

e. Example Hereinafter, the present invention will be specifically explained with reference to Examples.

[Example 1] Microcapsules were manufactured using 76 parts by weight of camphor as a core material, 20 quintillion parts by weight of stearyl alcohol as a wall material, and Atist part of hydrophobic silica fine powder (trade name: Aerosil) as a trace additive.

First, a core material was placed in a stirrer equipped with a cutter, and the core material was cooled to below -80 υ using liquid nitrogen.

After the core material was sufficiently cooled to a low temperature, it was pulverized and stirred for 2 minutes at a rotational speed of 15,000 to 25,000 rpm. At this time, liquid nitrogen was constantly supplied to maintain a low temperature in order to eliminate heat generation due to Mf@ between the fine powders and friction between the shaft portion. Next, the pre-cooled wall material and Aerosil were added to the finely pulverized core material and mixed and stirred at the same stirring speed as above.

By the above operation, microcapsules in which the surface of camphor powder was coated with stearyl alcohol were obtained in high yield.

When comparing the odor of this microcapsule with camphor of the same weight and same degree of crushing as the camphor used in this microcapsule, it was found that the microcapsule had less camphor odor, and a clear difference was observed. In addition, we measured the weight loss over time of the camphor content in the microcapsules and pure camphor, and the results shown in the figure were obtained, indicating that microencapsulation suppresses the sublimation rate of camphor as a core material. was recognized.

[Example 2] Microcapsules were prepared in the same manner as in Example 1 using 80 parts by weight of magnesium chloride dihydrate as the core material, 17 parts by weight of hydrogenated castor oil as the wall material, and type 3 hydrophobic silica powder. 4 g of MJ was added to obtain microcapsules in which magnesium chloride powder was coated with hydrogenated castor oil. Despite the fact that magnesium chloride is a highly deliquescent substance, the microcapsules maintained a smooth, powdery consistency even after one week had passed since their preparation.

10 Effects of the Invention As explained in detail, the method for producing microcapsules of the present invention improves the pulverization efficiency and facilitates pulverization because the core substance is pulverized at a temperature lower than room temperature. Therefore, microcapsules with small particle size can be easily produced. When using a material that is long and has high chemical or physical activity at room temperature as a core material, the core material is pulverized and absorbed by the wall material at a low temperature that sufficiently suppresses chemical or physical changes in the core material. Because of this, the degeneration of the core* quality,
Due to its activity, which has been difficult to achieve in the past, it is possible to microencapsulate solid substances in high yields while suppressing changes. During production, no water or organic solvents are used, so the drying process and wastewater treatment are indestructible, and work safety is high. Furthermore, microcapsules of any particle size can be easily produced, and microcapsules with a wide variety of purposes can be produced.

[Brief explanation of the drawing]

The drawing is a graph showing the measurement results of changes in burden over time in Example 1. Applicant Nippon Sanso Co., Ltd.

Claims (1)

[Claims] l) A core material made of a substance that is solid at room temperature is pulverized at a temperature lower than room temperature, and then the core material 9 is ground at this temperature. A method for producing microcapsules, characterized in that the core material is covered with a wall material by mixing and stirring the core material with the material. 2) The core material is a material that undergoes chemical or physical changes at room temperature, and the core material is crushed and mixed and stirred with the wall material at a temperature at which chemical or physical changes do not occur in the core material. The method for producing microcapsules according to claim 1, wherein the process is carried out at a temperature at which substantially no chemical or physical changes occur in the core substance. 3) The method for producing microcapsules according to claim 1 or 2, wherein the core material and wall material are crushed in a mixed state.