RU2096074C1 - Apparatus for dispersing and microencapsulating hydrophobic fluids - Google Patents

Abstract

FIELD: chemical engineering. SUBSTANCE: aim of invention is to encapsulate fluids with dissolved target additives. Apparatus contains reactor with synchronously operating ultrasonic vibration-emitting systems and generator. Reactor consists of two chambers interconnected through flanges: one for dispersing and the other for microencapsulating hydrophobic fluids. Between the chambers, there is a track filter with calibrated through pores installed incorporated into large-cell stainless steel gauze. Piezoelectric ultrasonic systems are contained in chambers and operate in matched modes. EFFECT: enhanced efficiency of operation. 1 dwg

Description

 The invention relates to dispersing equipment and can be used to obtain microcapsules containing hydrophobic liquids with target additives dissolved in them, such as, for example, color-forming components, drugs and others. Such microcapsules are used in information recording systems, in copying technology, color photography, in thermal indicator devices, in medicine, as well as in many other fields of science and technology.

 Existing device designs [1, 2] for dispersing liquid media are mainly determined by those energy influences that are used in this case.

According to the application [3], the proposed device (disintegrator) for dispersion has a standard valve system and partitions inside the housing with a number of cells of a tetrahedral shape. When liquid passes under high pressure (up to 5.0 • 10 ⁷ Pa) through the cells, it undergoes repeated impact and decompression effects. In places where compression and rarefaction waves are superimposed, cavitation, turbulence, and shear phenomena occur, which increases the degree of homogeneity of the medium being treated.

 In the patent [4] it is proposed to use ultrasonic vibrations as an energy factor. Three ultrasonic transducers are evenly spaced around the cylindrical reactor and mounted in steel sleeves welded to the outer wall of the reactor. Ultrasound is transmitted through a buffer liquid, in particular olive oil, and a wall to the liquid in the reactor. The intensity of the ultrasound is sufficient for the occurrence of cavitation and, therefore, the process of dispersion.

 The dispersant [5] contains an ultrasonic oscillation source, a mixing chamber with inlet and outlet pipes, a nozzle with cylinder-conical holes. At the exit of the nozzle, a turbulent rotational movement of flows with cavitation bubbles is formed.

 The disadvantages of the known devices include the fact that they do not provide the ability to obtain microdroplets of uniform size, and in devices such as a disintegrator, high pressures are used, which complicates the design and increases the energy intensity of the dispersion process.

 The closest in technical essence to the claimed object is a device for mixing and dispersing liquids [6], selected as a prototype, containing a mixing chamber, coaxial with which is installed a divider in the form of a truncated perforated cone, facing a smaller base in the direction of liquid unloading. Perforation on the cone is made with alternating round and trapezoidal holes. Magnetic emitters of ultrasonic vibrations are installed in front of the divider.

 This design of the device for mixing and dispersion also does not allow to obtain uniform in size particles of hydrophobic liquids and does not allow after dispersion to carry out the process of microencapsulation in a polymer shell.

 The main feature of the proposed invention is the need to develop and create a device with an ultrasonic oscillation source, which would allow simultaneously with the dispersion of the liquid hydrophobic composition to carry out the process of microencapsulation of its particles in aqueous solutions of film-forming substances.

 A positive result is achieved by the fact that the proposed device for dispersion and subsequent microencapsulation of hydrophobic liquids is structurally made in the form of two chambers connected to one unit by flanges. A polyethylene terephthalate (PETF) track (nuclear) filter with the required diameter of through pores is installed between the cameras; enclosed on both sides in a stainless steel mesh. The cameras have personal ultrasonic piezoelectric oscillatory emitting systems operating in coordinated modes from the generator. A check valve is installed on the inlet (discharge) pipe of the lower chamber.

 The invention is illustrated in the drawing, which shows a section of the proposed device.

A device for dispersing and microencapsulating hydrophobic liquids consists of two cylindrical chambers 1 (upper and lower) made of stainless steel. The cameras are connected using flanges. A track PET 3 filter 10 microns thick, mounted between two stainless steel grids 4 with a mesh size of 2 • 2 mm, is mounted in a flanged joint using fluororubber rubber gaskets (SKF-32 rubber grade). The diameter of the through pores of the track filter is 1 μm, their number per 1 cm ² is 4 • 10 ⁷ .

 The cameras contain ultrasonic piezoelectric emitters 8 operating synchronously from the generator brand UZG 3-04. The emitters are mounted in the chambers of the device through acoustic decoupling and are fixed with installation gaskets 7 made of oil-, gas-resistant rubber. The lower chamber of the device has a discharge pipe 6 with a non-return valve and a drain with a tap 5. The upper one contains two hatches, one 9 for installing the thermocouple sleeve, and the other 1 for loading the necessary solutions of film-forming substances, and also pipe 11 for draining the finished dispersion of microcapsules.

The proposed device allows dispersion of the emulsion of the starting components in the lower chamber to the required particle size of the hydrophobic liquid under the action of sound pressure forces in a pulsating mode and transport them through the filter. The presence of increased static pressure in the closed volume of the lower chamber (not more than 6.0 • 10 ⁴ Pa) prevents the reverse process. In the upper chamber, an ultrasonic flow captures fluid particles entering through the pores of the filter. Here, in a solution of film-forming substances, a polymer shell forms around each particle.

Due to the action of a high-amplitude ultrasonic field (22 ± 7.5% kHz), the emulsion is heated to 65–70 ^° C. At this temperature, the polymer shell is crosslinked (crosslinked). The whole process lasts from 1.5 to 2.0 hours.

 The mechanism of action of the device is based on the known ultrasonic capillary-cavitation effect.

 A pre-prepared emulsion of the oil / water type is pumped through the pipe with a check valve into the lower chamber of the device until it is completely filled (chamber capacity is 0.8 l). A solution of film-forming substances is loaded into the upper chamber to form microcapsule shells. The liquid level must be higher than the acoustic isolation of the emitter.

Using the generator UZG 3-04 in the chambers using oscillatory systems create a high-amplitude ultrasonic field and within 1.5 2 hours the process of dispersion in the lower and microencapsulation in the upper chamber. After completion of the process, the contents of the upper chamber are discharged through a drain pipe and filtered. The microcapsules remaining on the filter are dried at 60 ^° C. for 30–40 minutes under the vacuum created by the water-jet pump.

 Ready-made microcapsules containing a hydrophobic liquid with, for example, a color-forming component dissolved in it, are used for their intended purpose.

The proposed device allows microencapsulation of various chemicals, solvents, oils, catalysts, plasticizers, dispersions of fat-soluble pigments and dyes, photochromic compositions in liquid-phase media with a microcapsule size from 1 to 6 microns and with a polydispersity of 4 6%
The novelty of the device is:
in combining dispersion and microencapsulation processes in one unit;
in the use of two personal for each camera coordinated oscillatory emitting systems that create ultrasonic fields, provided that their maximum intensity is concentrated on the track filter;
in application for obtaining uniform (in size) microcapsules of track (nuclear) filters from thermo-, mechano- and chemically resistant polyester or polyimide films.

Sources of information
1. M. Gutcho. Capsule Fechology and Microcansulation. Noyes Data Corporation. Noyes Bilding. Park Ridge, New Jesty 07656, USA, 1972.

 2. Solodovnik V.D. Microencapsulation. M. Chemistry, 1980.

 3. Japanese application N 69152, C 12 M 1/100, 1/04, 1976.

 4. UK patent N 2243092, B 01 J 19/10, 1991.

 5. USSR patent N 1599075, B 01 J 11/100, 5/06, 1988.

 6. Auto USSR N 1599078, B 01 J 11/02, 1988 (prototype).

Claims (1)

 A device for dispersing and microencapsulating hydrophobic liquids, containing a reactor with ultrasonic oscillating emitting systems operating synchronously, and a generator, characterized in that the reactor consists of two chambers upper and lower with a check valve on the discharge pipe, each of the cameras is equipped with a personal ultrasonic piezoelectric oscillatory system and between the chambers connected by flanges, a polyethylene terephthalic track filter is installed, enclosed in a coarse mesh of stainless steel growing steel.