Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Compositions to be polymerized by wave energy wherein said...
Reexamination Certificate
2001-07-06
2003-05-20
Seidleck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Compositions to be polymerized by wave energy wherein said...
C522S170000, C522S176000, C522S074000, C522S081000, C522S083000, C204S157150, C204S157430, C264S489000, C523S300000, C526S088000, C526S089000, C526S090000, C526S266000
Reexamination Certificate
active
06566414
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method to cure epoxy resins in a short time by means of microwave radiation, and a method for absorbing electromagnetic wave using the cured epoxy resins which are obtained by said curing method.
2. Description of the Prior Art
The curing reactions of epoxy resins can be occur with its required energy such as heating, and propagate exothermically. And when reached to a certain level of curing reaction rate, the cured properties which are practically effective can be obtained. The cured epoxy resins obtained as above are generally in use as coating, adhesive, material for road paving, casting material, molding material, sealant, composite material and laminate, which are useful from the view point of industry. In general, as the heat source that heats material, infra red rays including far infra red rays radiated from hot air, steam, heater or gas burner are used, and the provided heat energy is transferred through complicated effect of radiation, convection and conduction to the surface of the material and is transferred from the surface to its inside.
The heating method to utilize an exothermic phenomenon by high frequency wave radiation is called as the radio frequency heating and in use widely. In case where the material to be heated is a conductor, it can be heated with eddy current which generates inside the conductor when it is set in a coil called induction in which high frequency electric current is streamed and is called induction light. In case where the materials are insulating ones such as plastics and woods, they are set between two electrodes in which high frequency voltage is charged and heated by dielectric loss. Since above-mentioned two cases, the materials can be heated homogeneously by a kind of inductive heat inside them. Therefore, these two types of heating are utilized for the homogeneous drying of woods, adhering and molding of plastics. These methods are called a microwave heating, because these methods use microwave with wave length of 0.1 mm to 1 m such as sub millimeter wave, millimeter one, centimeter one or decimeter wave. As the microwave to be used in this invention, the electromagnetic waves with 1 cm to 1 m wave length are desirably used. The frequency number of said microwave is 300 MHz to 30 GHz. Microwave ovens are a heating system unit to heat insulating materials which the above mentioned principle is applied that utilize above mentioned theory (refer to pages of 489 and 1529, Iwanami Physical and Chemical Dictionary 5th edition, February 98, Iwanami Shoten).
Accordingly, microwave-heating units have been developed vigorously for the purpose of industrial applications. Practical heating units have realized (Papers of 12th Japan Road Conference, Coating Technology. vol 3, 2000; Tsuneo Nakamura). However, actual applications which use the microwave heating and drying method are only for acid curing type, amino alkyd resin base coating paints and polyester-polyurethane type ones in the coating field. Further, in the case of melamine resin type coating, there have been a report that the microwave heating can not be applied, practically because the base resin is partially damaged by the microwave radiation. When the microwave heating is used, good effects are expected in the following. That is, reduction of drying time and the improvement of its operating efficiency could be attained. However, if the materials to make coating are not selected suitably, damage such as foaming observed in the case of melamine resin will occur. Because curing reaction take place quickly. In the case of a clay type material even when water inside the material can be vaporized, a constant rate period of drying cannot be made and directly shifted to a falling rate period. Therefore, transfer rate of vaporized water becomes very slow and pressure inside the coat raises and results in cracking there. Therefore, in this case, many examples that the microwave drying method cannot be substantially used have been known.
Up to this time, as the radio-frequency heating process for epoxy resin compositions, the heating and curing method of fiber reinforced plastics by microwave radiation has been proposed (Japanese Patent Publication 5-79208). This method is specialized as the method to heat and cure a reinforced plastic by microwave radiation and, characterized by settling a molded product of fiber reinforced plastics into a mold made of a material with exothermic reaction by microwave radiation and includes microwave radiation to said molded product and the mold to cause a curing reaction of the molded product and the mold with heat generation. And for Kebler fiber reinforced epoxy resin type prepreg is mentioned as typical example for the fiber reinforced plastics. Further, as the said method to cure a resin molded product, the method to contain molding material composed mainly of a uncured thermosetting resin in a mold which easily conducts electromagnetic wave, and radiate electromagnetic wave from the outside of the mold so as to heat the mold and the above resin at one time is proposed (Japanese Patent Laid open Publication 11-300766). As the thermosetting resin, a modified epoxy resin which has a polar group, a modified epoxy resin obtained by the reaction between carboxyl group containing fatty acid modified urethane compound and epoxy resin and the mixture of said modified epoxy resins and glycidyl ether resins are described as example. Further, as another method, post curing (post curing method) characterized by microwave heating to heat thermosetting resin molded products and post cure them has been disclosed (Japanese Patent Laid-Open publication 9-109271).
These mentioned examples have no intention and are not any method to cure an epoxy resin composition by direct microwave radiation in it, but a method to use heat induced by microwave radiation to a mold as heat to cure the resin are limited to a case that the epoxy resin itself is a very special resin, or a method of post curing after almost completion of the curing.
Epoxy resins are very useful as coating to coat a structural materials, anti-corrosive coating for concretes, repairing materials for concretes, materials for road paving, epoxy asphalt materials and insulators for electric and (or) electronic parts, because of their excellent features such as adhesivity, anti-corrosivity, anti-chemical properties, insulating and mechanical properties. The hardening mechanism of epoxy resins used for above-mentioned applications is illustrated as follows. That is, epoxy resins of lower molecule weight and curing agent are initiated to heating at ambient temperatures or under the temperature raising condition and form cross linked structures so as to form a cross linked and cured coating film of polymer. In general, to progress this curing reaction, it is necessary to heat epoxy resin compositions at temperatures higher than 200° C. for 10 to 30 minutes or eventually several hours. For the realization of this curing process, a large scale drying furnace and wide plant site are required to install it. Therefore, the corresponding the total plant cost is very expensive and is not to be practical when it will be set temporally in a construction field. In the meanwhile, in case of ambient temperature curing method, epoxy resin and curing agent can be prepared separately and respectively mixed at the practical use point. In this case, if a type of short time curing agent is used, the available time of the cured product is remarkably shortened, and subsequently the blending volume of epoxy resin and curing agent is limited to incur a problem that the processing characteristics efficiency decrease remarkably. And, when the curing time is adjusted to be longer, the time to give the initial practical strength to the cured product is delayed, and the problem that the road opening time after road repairing is delayed increasingly might occur. Further more, to avoid the troublesome due to mixing of two liquids at the actual constructio
Matsuura Makoto
Nakanishi Hiroshi
Shimizu Takashi
Takeshima Hideo
Yoshino Takao
McClendon Sanza L.
Nippon Liner Co., Ltd.
Seidleck James J.
Sherman & Shalloway
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