Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Compositions to be polymerized by wave energy wherein said...
Reexamination Certificate
1999-06-17
2003-07-29
Berman, Susan W. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Compositions to be polymerized by wave energy wherein said...
C522S026000, C522S028000, C522S031000, C522S071000, C522S081000, C522S083000, C522S170000, C442S149000, C442S150000, C442S409000, C156S272800, C156S273300, C156S273500, C156S275500, C156S307100, C156S307300
Reexamination Certificate
active
06599954
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a resin curing method for curing resins rapidly by means of energy radiation such as ultraviolet radiation (UV), electron beam (EB), infrared radiation, X-rays, visible light, light from lasers (e.g., argon, CO
2
and excimer lasers), sunlight and radiated heat rays, and other energy such as heat, and to polymerization initiators and compositions which enable resins to be cured by this method, molded articles made therefrom, and their production methods and apparatus.
More particularly, the present invention relates to a resin curing method for thick-walled resins in which energy radiation is attenuated or absorbed by the resin to cause a marked reduction in curing action and, therefore, the deep part thereof cannot be cured, and for resins reinforced with fillers (e.g., carbon fiber, metallic fibers and glass fiber) or metallic inserts in which energy radiation is screened by such reinforcing materials and, therefore, the shaded part of the resin cannot be completely cured, and to polymerization initiators and compositions which enable such resins to be cured by this method, molded articles made therefrom, and their production methods and apparatus.
The present invention also relates to a novel resin curing method which enables the energy radiation curing of resin systems containing substances highly capable of screening radiation energy (e.g., carbon, carbon fiber (CF), metals and other inorganic fillers), such as carbon fiber-reinforced composite materials (CFRPS) and carbon/metal/inorganic matter-containing resins, and to compositions therefor, molded articles made therefrom, and their production methods.
The present invention also relates to a method of making a fiber-reinforced composite material (FRP) wherein a composition capable of inducing the novel resin curing mechanism in the aforesaid resin curing method is used as the matrix resin, and a reinforcing fiber (e.g., CF) is impregnated with this resin and then cured by means of energy radiation typified by UV.
The aforesaid curing method, compositions, molded articles and molding methods are effective without regard to the UV screening properties of fibers or fillers, and the length, size and shape thereof. Moreover, they can be utilized not only in the field of composite materials, but also in the fields of adhesives, sealers, varnishes, paints, coating materials, inks, toners and the like.
BACKGROUND ART
In recent years, energy radiation-curable resins typified by UV-curable resins are being used in various fields and applications. These resins are characterized in that they are cured only in regions exposed to more than a certain amount of energy radiation. On the other hand, energy radiation typified by UV radiation is characterized in that it is attenuated while it passes through a resin. As a result, it is difficult for energy radiation to reach the deep part of a resin, or energy radiation is greatly attenuated or absorbed, for example, in the presence of a substance capable of absorbing a wavelength equal to that of the energy radiation. Thus, photo-curable resins are cured only in a surface layer having a thickness of several micrometers to several millimeters through which energy radiation can pass, and the deep part thereof remain uncured. Consequently, it is difficult or impossible to apply photo-curable resins to thick-walled materials. Moreover, in the case of resins containing fillers and other substances hindering the passage of energy radiation, they tend to undergo inhibition of their cure and hence become incurable. Owing to these problems, their application has been chiefly limited to the fields of photoresists, coatings, paints, adhesives, varnishes and the like.
Typical solutions to these problems are offered by highly UV-curable resins (Mitsubishi Rayon Co., Ltd.; active energy radiation-curable compositions; Japanese Patent Provisional Publication No. 8-283388/'96) and UV- and heat-cocurable resins {Optomer KS series (Asahi Denka Kogyo K.K.); Radicure (Hitachi Chemical Co., Ltd.); UE resin (Toyobo Co., Ltd.); Japanese Patent Publication (JP-A) No. 6-38023/'86; and the like}. However, highly UV-curable resins still have the problem that they cannot be cured when energy radiation is blocked by a filler or the like. Moreover, in UV- and heat-cocurable resins which are cured by heating after exposure to UV radiation, their energy radiation curability is similar to that of conventional photo-curable resins, and the problems associated with the curing of thick-walled resins and filler-containing resins remain entirely unsolved. Thus, under the existing circumstances, these problems cannot be solved and are hence coped with by heat curing subsequent to photo-curing (of a surface layer alone).
If a technique by which the above-described thick-walled resins containing an energy radiation screening substance or highly capable of attenuating or absorbing energy radiation can be cured rapidly is established, this technique may be applied not only to conventional fields of application, but also to various other fields in which the application of energy radiation curing has been impossible owing to the problems of photo-curable resins. One example thereof is application to the matrix resins of FRPs, particularly CFRPs.
Conventionally, a variety of processing techniques and production processes are employed for FRPs, but the matrix resin consists of a thermosetting or thermoplastic resin in most cases. The problems associated with the molding of FRPs, particularly CFRPs, are that high processing costs are involved because a long curing time results from complicated temperature control, a large-sized heating oven is required for the curing of large-sized FRPs, resins capable of being cured at room temperature in a short period of time cannot be used for large-sized FRPs requiring a long curing time, the molding of FRPs is difficult because the resin-impregnated state varies according to changes in resin viscosity with temperature, and the formation of voids arises from residual solvent during the curing of the resin and causes a reduction in the quality of the molded article.
Recently, as a solution to these problems, the utilization of a photo-curable resin as the matrix resin is attracting attention. A particular and typical example of this matrix resin curing method is the filament winding molding process of Loctite Corp. which uses a combination of UV curing and heat curing (Loctite Corp.; Fiber/resin composition and its preparation method; Published Japanese Translation of PCT International Publication No. 7-507836/'95). However, in the FRP molding process using such a composition, an uncured resin-impregnated FRP is irradiated with UV radiation so as to cure its surface and so as thicken (or gelatinize) its inner part extremely and thereby enable the maintenance of its shape and resin-impregnated state to some extent, and then heated to achieve a complete cure. Accordingly, as compared with the conventional production process using a thermoplastic or thermosetting resin, the change in resin viscosity with temperature is very slight and the handling of the FRP after resin impregnation is easy, but a heat curing step is still required in order to achieve a complete cure. Thus, the problem of high processing costs arising from the fuel and light expenses and operating time required for heat curing, the problem of a long curing time, and the need for a large-sized heating oven in the molding of large-sized FRPs remain unsolved.
DISCLOSURE OF THE INVENTION
In view of the above-described disadvantages of conventional resins cured by energy radiation and the above-described disadvantages of FRPs, particularly CFRPs, the present inventors made intensive investigations on the energy radiation curing of thick-walled resins containing an energy radiation screening substance (i.e., a substance capable of screening energy radiation) and the energy radiation curing of FRPs, particularly CFRPs, and have now attained the present invention. An ob
Hayashi Noriya
Hayashi Shun-ichi
Berman Susan W.
Mitsubishi Heavy Industries Ltd.
Myers Bigel & Sibley & Sajovec
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