Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Process of treating scrap or waste product containing solid...
Patent
1998-10-15
2000-05-09
Niland, Patrick D.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Process of treating scrap or waste product containing solid...
264911, 528499, 528502R, 528502C, 528503, C08J 1104, C08J 300, C08F 600, C08G 6400
Patent
active
060605278
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a process for recovering a resin as a substrate contained in optical information recording media coated with a thin metal film layer and a printed coating film layer. More particularly, it relates to a process for selectively removing the thin metal film layer and the printed coating film layer from the above optical information recording media and recovering the resin component as a substrate for recycling.
PRIOR ART
There have been developed and made commercially available various optical information recording media such as those using a mode of regenerating sounds or images by detecting the fine unevenness formed at the surface of the disc substrate by means of a laser beam, those using a mode of recording and regenerating information based on the information recording layer formed on the substrate, those using a mode of enabling the recorded information to be erased or overwritten, and those having increased memory capacity by laminating any of the substrates used in the above media. These information recording media must have a large and extremely high-density memory capacity and be of high quality. Therefore, they must be treated as defective when even a very small defect is found. Moreover, the test samples taken out from various steps of production process for the verification of high quality are inevitably large in number. In particular, compact discs for replay only are produced in a large number, and disposal of a large number of resin plates including test samples, defectives and products recovered from market raises a problem.
These recording media have been produced using transparent resins such as polycarbonate resin, polymethyl methacrylate resin, amorphous cyclic polyolefin resin and the like. Of these, the polycarbonate resin is used in most of compact discs and in a large scale production. On the other hand, the use of the polycarbonate resin also produces a large number of test samples, defectives, etc. In disposing these test samples, defectives, etc., transparent optical substrates before neither an information recording layer nor a reflecting layer is applied can be ground or re-pelletized to be mixed with an ordinary polycarbonate resin or with its alloy with other resins for proper recycling. However, in the case of the resin plates on which an information recording layer, a reflecting layer, a protective coat layer such as UV coat, and an adhesive layer for lamination (may be referred to as "coated resin plates" hereinafter) are formed, its recycling is significantly restricted. For example, in the case of a resin plate having a UV coat layer formed thereon, since the UV coat layer is incompatible with polycarbonate resins, mere mixing of said resin plate with an ordinary polycarbonate resin and molding of the mixture gives a molded product having surface unevenness and very bad appearance. In the case of a laminated resin plate, since the adhesive used therein has thermal stability inferior to that of the resin used therein, there may arise, when reused, deterioration of color and reduction in resin molecular weight.
Therefore, proposals were made with an aim of selectively removing the information recording layer, the reflecting layer and the protective coat layer from a coated resin plate and recovering the resin itself of the plate.
Some of these proposals are described below.
(i) Japanese Laid-Open Patent Applications Nos. 4-305414 (European Patent No. 476,475, U.S. Pat. No. 5,151,452), 5-200379 (European Patent No. 537,567, U.S. Pat. No. 5,214,072) and 6-223416 (European Patent No. 601,719, U.S. Pat. No. 5,306,349)
The methods disclosed in these literatures are a method which comprises treating a coated resin plate chemically with, for example, an aqueous solution of an acid or an alkali, that is, a method which comprises dissolving the metal portion of the information recording layer and reflecting layer of a coated resin plate and thereby removing the UV coat layer and the label printing layer. The method has had a drawb
REFERENCES:
patent: 5151452 (1992-09-01), Fennhoff et al.
patent: 5203067 (1993-04-01), DeFazio
patent: 5214072 (1993-05-01), Fennhoff et al.
patent: 5306349 (1994-04-01), Nee
Nakado Tomohiro
Nakahiro Hideki
Shinomiya Hiromasa
Niland Patrick D.
Teijin Chemicals Ltd
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