There is presently a desire to achieve higher precision and higher density in semiconductor sealing materials, underfill materials, sealants, adhesives, insulating materials, solder masks, and dry films for the purpose of reducing the size and the weight of portable equipment and increasing communication speed. Under these circumstances, there is a desire for the materials having properties such as higher stability, flowability, and heat resistance. There is also a desire to develop a method for producing a curing catalyst in particulate form usable for a composition constituting the materials.
Conventionally, there have been reported many methods for preparing particulates (microcapsules) composed of a core material and a polymer material coating the core material. The known methods use a dispersion system such as an emulsion polymerization method, a suspension polymerization method, an interface reaction method, or a submerged drying method. These methods have advantages such that no special equipment is required, the size of particulates is easy to adjust to some degree, and the properties and the structures of particulate membranes can be controlled. Thus, the methods are utilized in various fields, for example, in practical use for pressure sensitive copying papers, pressure measurement sheets, pressure sensitive adhesives, liquid crystal display materials, controlled release pharmaceuticals, and controlled release agricultural chemicals.
The conventional production methods, however, have a tendency that only components of particulates according to each method are applicable for producing more uniform particulates. This causes a problem of narrowing the scope of selection of components. In addition, the properties of particulates to be obtained considerably depend on parameters of particulate size and membrane thickness (the diameter and the thickness of a wall membrane) of particulates. Therefore, in order to make particulates to have excellent properties uniformly, it is necessary to control the particulate size and membrane thickness within a proper range. However, particulates are conventionally produced by techniques such as forming lumps of core materials in a liquid by dispersion using a dispersing agent and stirring. In employing this production method, the particulate size and membrane thickness of microcapsules are controlled by adjusting the rate of stirring or the concentration of a dispersing agent, resulting in variation in both of the particulate size and the membrane thickness. In summary, it is difficult to control microcapsules precisely such that the microcapsules have a desired level of particulate size and membrane thickness, and further make the microcapsules uniform.
In order to overcome the problems, Patent Document 1 discloses a method of producing microcapsules (phase separation method, submerged drying method, interfacial polymerization method, or in situ polymerization method) by ejecting a liquid composition composed of a polymer material to form a membrane and a core material into a solution by an inkjet method. The method is excellent in that the particulate size of microcapsules can be controlled precisely.
The method, however, has a drawback that obtained microcapsules are required to be separated from the liquid into which the composition is ejected. The method has many unsolved industrial and environmental problems such that it takes much time to separate microcapsules having a particulate size on the order of millimeters to nanometers by filtration, and large amounts of a cleaning fluid are required to wash the microcapsules.
Patent Document 1: JP-A-2001-232178
An object of the present invention is to provide a method for producing a curing catalyst in particulate form that remains stable and flowable for a long time after a base compound and a curing agent are combined into one pack, and usable for a composition compatible with high performance of present underfill materials, sealants, adhesives, insulating materials, solder masks, or the like. Another object of the present invention is to provide a method for producing a curing catalyst in particulate form of which particulate size is controlled precisely and uniformly, and the produced catalyst can be separated and extracted easily.