a new fluidized bed coating process via photo-initiated cationic polymerization.
The recent paper reviews its principles and practices (1-3).
In a typical fluidized bed, particles are suspended and cycled by air flow.
Depending on the size, shape and density of the particles, the air flow rate needs to be set within the range between the minimum flow rate and the pneumatic delivery.
The coating solution is delivered to the flow chamber through the Atomization Nozzle, atomization into droplets, and then spread to the surface of the flow particles.
The evaporation of the coating solvent leaves a solid solvent on the surface.
The evaporation rate is generally slow, depending on many parameters such as temperature and relative humidity of the air, air flow rate, coating solvent and particle properties (
Size, size distribution, surface roughness)
Make the drying process expensive, may not be friendly to the environment, time-
It is difficult to be controlled precisely.
Another serious problem encountered in this boiling bed coating is unnecessary interparticle reunions, mainly caused by a liquid bridge formed between wet particles.
This may result in a rapid flow-off or even closure of the coating process, especially for the coating of small particles.
Therefore, it is important to develop a solvent
Free fluidized bed coating process with less particle aggregation.
One method is to use the appropriate polymerization method to apply the coating directly to the surface of the particles through the polymerization of the monomer or premix liquid in the fluidized bed coal. Photo-
Aggregation has aroused great interest in the past 20 years because of its increasing relevance in industrial applications, such as UV-
Surface coating can be cured.
There are two types of photos
Polymerization mechanism widely used in paint industry: Free Radical Light-
Photo of polymerization and cationpolymerization.
In atypical free radical polymerization, three-by polymerization of multi-functional acrylic monomer-
Through the dimension network of photos
Induced decomposition of radical initiator.
Acrylic monomer and photos
The initiator for specific purposes has been developed and commercialized by chemical companies such as Sartomerand Dow Chemical. Studies (3-7)
UV has been proven.
Free curing paint
Free Radical Polymerization is easily inhibited by oxygen, so it may lead to a sticky surface in an atmospheric environment. Cationic photo-
Promoters such as iodine and sulfur salt pair produccecross-
Film of epoxy monomer connection.
The initiator accepts ahemolytic C--I (or C--S)
The bond breaks and produces positive ions of benzene iodine free radicals (
Or a positive ion based on benzene sulfon)
This will start the ring further-
Open polymerization of epoxy monomer.
Cation polymerization has some advantages compared to free radical, such as insensitivity to oxygen, small shrinkage, good adhesion to various surfaces and the ability to \"dark cure.
\"Some research has been done to study the photo of the cation
Polymerization of epoxy compounds or functional epoxy resin
In this study, a new particle coating process was successfully developed by fluid-fluid couplingized-
Bed coating with photo
As shown in the figure.
1. By including a transparent quartz cylindrical window in the particle \"origin\" area of the chamber, the regular boiling bed coating machine was modified.
The window allows UV light generated by Mercury UV lamps to penetrate the wall of the coating machine to reach the surface of the flowing particles, where UV-
Cured compounds are pre-coated and then quickly
Curing after UV irradiation.
The process is environment-friendly compared to conventional fluidized bed coatings, as it does not involve volatile or/and toxic solvents.
Polymerization is usually so fast that UV-
Curing can be done in a few seconds, which makes it possible to significantly shorten the processing time of the boiling coating. [
Figure 1 slightly]
Choosing the right polymerization system is critical for drying and stickiness
Free coating on particles during coating process.
Recently, we have extensively studied the curing dynamics of acrylic supermolecules.
Film coating on [A1. sub. 2][O. sub. 3]
Radical mechanism (14).
It is found that the presence of oxygen always leads to a very low conversion rate of acrylic monomer, so it is difficult for air
The driven fluidized bed is free-
Mechanism of radical polymerization.
Taking into account the advantages of cation photos
Polymerization on the free radical photopolymerization described earlier, this study focuses on the development of an active polymerization system containing epoxy monomer that experiences spontaneous and spontaneous in the presence of oxygen generation in a fluidized bed
Epoxy resin due to its ideal properties, many important industrial applications have been found, including adhesion to many substrates, chemical resistance and high strength (15-17). Bilyeu et al. (18)
In the in-depth study of the usingtemperature of the epoxy resin system of thegelation, glass transition, fully cured-modulated DSC (TMDSC)
Dynamic Mechanical Analysis (DMA).
Since the degree of curing is critical to the boiling bed coating process in the study and may affect the properties of coated particles, such as viscosity and fluidity, we have studied the curing dynamics of epoxy thin coatings on particles with light
Differential Scanning heat (photo-DSC)
And Fourier transform infrared spectrum (FTIR).
According to the specific engineering requirements of the fluidized bed coating process, the epoxy resin curing system was formulated.
Experimental material potassium chloride (KC1)particles (40-200 mesh)
It was purchased from Reheis.
Pre-coated particles 0. 2% (w/w)
Use the gas phase method silicone of the rotary drum coating machine.
The specific surface area of gas phase silica is 130 [m. sup. 2]
/G, the average particle size is 16 nm (AEROSIL[R]
R 972, win the record). Ultra-dry air ([H. sub. 2]O content