Stock material or miscellaneous articles – Circular sheet or circular blank
Reexamination Certificate
1999-03-31
2001-06-12
Evans, Elizabeth (Department: 1774)
Stock material or miscellaneous articles
Circular sheet or circular blank
C428S064400, C428S064500, C428S412000, C428S913000, C430S270110, C430S945000, C528S499000, C528S503000
Reexamination Certificate
active
06245405
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an optical molding material that is an aromatic polycarbonate resin pellet. More specifically, it relates to an aromatic polycarbonate resin pellet that hardly produces fine powders during transportation, conveyance or storage thereof and is suitable for use as an optical molding material.
The present invention also relates to a process for producing an aromatic polycarbonate resin pellet that hardly produces fine powders and to an optical disk substrate formed from the resin pellet.
PRIOR ART
Since aromatic polycarbonate resins (may be simply abbreviated as “PC resins” hereinafter) have high transparency and excellent heat resistance and dimensional stability, they are used as an optical recording materiel such as an optical disk material. A typical optical disk made from such a PC resin is a compact disk (CD). The development of DVD, DVD-ROM and DVD-RAM, having larger recording capacity,, especially higher recording density, is also recently under way.
The PC resins for use as a material for these optical disks are required to have high quality. It is known that the content of resin fine powders in a PC resin pellet has an influence upon the properties and quality of a molded product. It is also known that, when the content of resin fine powders in a PC resin pellet to be molded is more than or equal to a predetermined amount, an optical disk molded from the pellet has various defects as a recording material due to the formation of a carbide. For example, JP-B 6-18890 (the term “JP-B” as used herein means an “examined Japanese patent publication”) discloses that the content of a powdery polymer, contained in a PC resin pellet and having an average particle diameter of 0.5 mm or less, should be 2.0 wt % or less.
Heretofore, the amount of fine powders contained in a PC resin pellet has been measured by screening the produced pellet directly, washing it with water, or the like.
The measurement result of the amount of fine powders by a manufacturer or supplier does not always reflect the amount of fine powders contained in a pellet used by a pellet user (molder of a substrate). For example, even if the amount of fine powders contained in a pellet supplied from a manufacturer is small, the amount of fine powders may increase and may influence the quality of a molded substrate when a user uses the pellet. Resin fine powders are produced from the surface of the pellets because the pellets collide or contact with one another or with an apparatus during conveyance, storage or pipe transport between the shipment: of the pellets by the manufacturer or supplier and the arrival thereof to the user. The amount of fine powders produced from the PC resin pellet is not fixed because it is influenced not only by the shape and properties of the pellet but also by its conveyance, storage and pipe transport conditions. Therefore, the manufacturer or supplier of the PC resin cannot accurately know the amount of fine powders contained in each pellet that is actually used for molding. In other words, the relationship between the amount of fine powders and the amount of a carbide contained in an optical disk cannot be accurately clarified.
SUMMARY OF THE INVENTION
It is an object of the present invention to clarify the relationship between the amount of fine powders and the amount of a carbide formed by knowing the amount of fine powders contained in a resin pellet that is actually used to produce an optically molded product and to provide a resin pellet that produces fine powders only in an extremely small amount during its transportation, conveyance or the like.
The inventor of the present invention has conducted studies to achieve the above object and has found that the amount of fine powders contained in a transported or conveyed pellet can be estimated by controlling the amount of fine powders produced by shaking resin pellets together to mix for a predetermined time. The inventor has also found that a resin pellet which hardly produces fine powders can be produced by improving the method of cooling a strand for producing the resin pellet and a temperature condition.
The present invention has been accomplished by the above findings. The present invention relates to an optical molding material that is an aromatic polycarbonate resin pellet characterized in that the amount of fine powders, produced by mixing 5 kg of the pellets in a vessel for 1 hour and having a particle diameter of 1.0 mm or less, is 300 ppm or less, preferably 250 ppm or less, more preferably 150 ppm or less.
The resin pellet of the present invention hardly produces fine powders during its transportation or delivery, the manufacturer or supplier of the resin pellet can control the amount of resin fine powders at the time of using the resin pellet (molding), and a high-quality resin pellet for optical disks can be supplied to a user.
The present invention will be described hereunder in more detail.
The aromatic polycarbonate resin in the present invention is generally obtained by reacting a divalent phenol with a carbonate precursor in accordance with a solution or melting process. Typical examples of the divalent phenol used herein include hydroquinone, resorcinol, 4,4′-dihydroxydiphenyl, bis(4-hydroxyphenyl)methane, bis{(4-hydroxy-3, 5-dimethyl)phenyl}methane, 1,1-bis(4-hydroxyphenyl) ethane, 1,1-bis(4-hydroxyphenyl)-1-phenylethane, 2,2-bis(4-hydroxyphenyl)propane (generally called “bisphenol A”), 2,2-bis{(4-hydroxy-3-methyl) phenyl}propane, 2,2-bis{(4-hydroxy-3,5-dimethyl) phenyl}propane, 2,2-bis{(3,5-dibromo-4-hydroxy) phenyl}propane, 2,2-bis{(3-isopropyl-4-hydroxy) phenyl}propane, 2,2-bis{(4-hydroxy-3-phenyl) phenyl}propane, 2,2-bis(4-hydroxyphenyl)butane, 2,2-bis(4-hydroxyphenyl)-3-methylbutane, 2,2-bis(4-hydroxyphenyl)-3, 3-dimethylbutane, 2,4-bis(4-hydroxyphenyl)-2-methylbutane, 2, 2-bis(4-hydroxyphenyl)pentane, 2,2-bis(4-hydroxyphenyl)-4-methylpentane, 1,1-bis(4-hydroxyphenyl)cyclohexane, 1,1-bis(4-hydroxyphenyl)-4-isopropylcyclohexane, 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane, 9,9-bis(4-hydroxyphenyl) fluorene, 9,9-bis{(4-hydroxy-3-methyl)phenyl}fluorene, &agr;, &agr;′-bis(4-hydroxyphenyl)-o-diisopropylbenzene, &agr;,&agr;′-bis(4-hydroxyphenyl)-m-diisopropylbenzene, &agr;,&agr;′-bis(4-hydroxyphenyl)-p-diisopropylbenzene, 1,3-bis(4-hydroxyphenyl)-5,7-dimethyladamantane, 4,4′-dihydroxydiphenyl sulfone, 4,4′-dihydroxydiphenyl sulfoxide, 4,4′-dihydroxydiphenyl sulfide, 4,4′-dihydroxydiphenyl ketone, 4,4′-dihydroxydiphenyl ether, 4,4′-dihydroxydiphenyl ester and the like. They may be used alone or in admixture of two or more.
Of these, preferred are homopolymers and copolymers obtained from at least one bisphenol selected from the group consisting of bisphenol A, 2,2-bis{(4-hydroxy-3-methyl) phenyl}propane, 2,2-bis(4-hydroxyphenyl)butane, 2,2-bis(4-hydroxyphenyl)-3-methylbutane, 2,2-bis(4-hydroxyphenyl)-3, 3-dimethylbutane, 2,2-bis(4-hydroxyphenyl)-4-methylpentane, 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane and &agr;, &agr;′-bis (4-hydroxyphenyl)-m-diisopropylbenzene, and particularly preferred are a homopolymer of bisphenol A and a copolymer of 1,1-bis(4-hydroxyphenyl)-1,3,5-trimethylcyclohexane with bisphenol A, with 2,2-bis{(4-hydroxy-3-methyl) phenyl}propane or with &agr;, &agr;′-bis(4-hydroxyphenyl)-m-diisopropylbenzene.
The carbonate precursor is selected from carbonyl halide, carbonate ester and haloformate, as exemplified by dihaloformates of phosgene, of diphenyl carbonate and of divalent phenols.
When a polycarbonate resin is produced by reacting the above divalent phenol with the above carbonate precursor in accordance with a solution or melting process, a catalyst, a terminating agent and an antioxidant for a divalent phenol. may be used as required. The polycarbonate resin may be a branched polycarbonate resin containing a polyfunctional aromatic compound having a functionali
Evans Elizabeth
Teijn Chemicals Ltd
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