Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-03-08
2001-03-20
Sanders, Kriellion (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C252S405000, C252S406000, C252S407000
Reexamination Certificate
active
06204311
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a (thio)epoxy compound suitably used in the field of resins such as optical materials including plastic lenses, prisms, optical fibers, information recording media and light emitting diodes which are required to have a high refractive index and a high transparency, as well as resins therefrom.
This invention also relates to a polymerizable composition suitably used as a starting material for a plastic lens for eyeglasses.
2. Description of the Related Art
A plastic lens is lighter and less brittle than an inorganic lens, and dyeable, which has been therefore rapidly prevailing in the areas of optical devices such as a lens of eyeglasses and a camera lens. Such a plastic lens is required to exhibit optical properties including a high refractive index and a high Abbe number and physical properties including high heat resistance and a low specific gravity.
Among these, high heat resistance and a low specific gravity have been considerably achieved by a current plastic lens with a high refractive index. Currently, the resins which may be widely used for these applications, include those prepared by radical polymerization of diethylene glycol bis(allylcarbonate) (referred to as “D.A.C.”). These resins have various features such as excellent impact resistance, lightness, excellent dye-affinity, and good processability including machinability and abradability. These resins, however, have a low refractive index (nd) of about 1.50, leading to a lens with thick center and margin. Thus, there is a need for a resin for a lens with a higher refractive index.
Resins with a higher refractive index than D.A.C. resin are known; for example, polythiourethane resins (e.g., JP-A 63-46213); sulfur-containing O-(meth)acrylate resins (e.g., JP-A 1-128966, 3-217412 and 4-16141); and thio(meth)acrylate resins (e.g., JP-A 63-188660 and JP-B 3-59060), in which sulfur atoms are introduced. A polythiourethane resin is well-balanced in its properties, that is, having suitable properties such as a high refractive index and good impact resistance.
A refractive index and an Abbe number are, however, conflicting properties; as the refractive index increases, the Abbe number decreases. It is, therefore, quite difficult to simultaneously improve these properties. Thus, it has been intensively investigated to achieve a high refractive index, preventing an Abbe number from being decreased.
Most typical suggestions of these attempts are processes using a (thio)epoxy compound as described in JP-As 9-110979, 9-71580 and 9-255781.
According to the processes, a high refractive index can be achieved while maintaining a relatively high Abbe number. A resin prepared according to these processes exhibits a refractive index of nd=about 1.70. Thus, it cannot be considered to meet the need for an improved refractive index sufficient to make a margin of an eyeglass significantly thinner while maintaining a high Abbe number, compared with a commercially available common lens with nd=1.67. An thioepoxy resin prepared from an thioepoxy compound tends to turn yellow during heating in a secondary process, long-term storage or its use. Such yellowing may cause tone alteration of an eyeglass which is required to be fashionable. Thus, it may not meet the needs of routine users of eyeglasses. A procedure for solving the problem has been suggested in, e.g., JP-A 10-298287, where a thiol compound is added to an thioepoxy compound to prevent yellowing. Although such a process can prevent yellowing, addition of a thiol compound, especially a mono- or bis-functional thiol, may cause significant deterioration of heat resistance, resulting in a lens which cannot give sufficient properties for an application requiring higher heat resistance.
SUMMARY OF THE INVENTION
An objective of this invention is to provide a polymerizable composition which can be used to prepare a resin having a very high refractive index and a high transparency, specifically having nd of 1.71 or higher, maintaining a high Abbe number.
Another objective of this invention is to provide a polymerizable composition which can give a resin maintaining a high refractive index and a high heat resistance, and which can prevent yellowing.
The inventors have intensely investigated to solve the above problems and finally have found that a higher refractive index can be provided by using a (thio)epoxy compound having at least one intramolecular disulfide bond which has been believed to be unstable (e.g., Reld.E.E., Organic Chemistry of Bivalent Sulfur Vol.3).
Specifically, one aspect of this invention is a polymerizable composition comprising a (thio) epoxy compound having at least one intramolecular disulfide bond. We have found that the polymerizable composition can be cured to give a resin with a high refractive index of nd=1.71 or higher.
There has been no information for physical properties or other characteristics of a polysulfide polymer prepared by curing a polymerizable composition containing a (thio)epoxy compound comprising at least one intramolecular disulfide bond.
The second aspect of this invention is a polymerizable composition comprising one or more compounds selected from the group of compounds having at least one NH
2
group and/or at least one NH group per a molecule as a yellowing inhibitor, having a total molar ratio of 0.001 to 0.5 of NH
2
and NH groups in the inhibitor to thioepoxy and epoxy groups in the (thio)epoxy compound comprising at least one intramolecular disulfide bond. We have found that a resin from the second polymerizable composition of this invention exhibits a high refractive index and a high Abbe number without heat resistance reduction or yellowing.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The first aspect of this invention will be described in detail.
A polymerizable composition comprising a (thio)epoxy compound having at least one intramolecular disulfide bond according to the first aspect of this invention contains at least one epoxy or thioepoxy compound having a disulfide bond and an epoxy or thioepoxy group. The composition may contain inorganic and/or organic compounds including polyether or polysulfide oligomers such as dimers, trimers and tetramers thereof, inorganic and organic acids added as a polymerization retarder, solvents or other by-products as long as they are not harmful.
In the specification, the term “(thio)epoxy” means thioepoxy or epoxy. Thioepoxy is represented by the following structure:
A (thio)epoxy compound having at least one intramolecular disulfide bond includes (thio)epoxy compound having one intramolecular disulfide bond such as bis(2,3-epoxypropyl) disulfide and bis(2,3-epithiopropyl) disulfide; (thio)epoxy compounds having two or more intramolecular disulfide bonds such as bis(2,3-epithiopropyldithio)methane, bis(2,3-epithiopropyldithio)ethane, bis(6,7-epithio-3,4-dithiaheptane) sulfide, 1,4-dithian-2,5-bis(2,3-epithiopropyldithiomethyl), 1,3-bis(2,3-epithiopropyldithiomethyl)benzene, 1,6-bis(2,3-epithiopropyldithio)-2-(2,3-epithiopropyldithioethylthio)-4-thiahexane and 1,2,3-tris(2,3-epithiopropyldithio)propane. Among the compounds, (thio) epoxy compounds having one intramolecular disulfide bond represented by formula (1) are preferred. Besides the process described in the document, bis(2,3-epithiopropyl) disulfide can be prepared by reacting bis(2,3-epoxypropyl) disulfide with a sulfurating agent such as a thiocyanate, thiourea, triphenylphosphine sulfide and 3-methylbenzothiazol-2-thione, preferably a thiocyanate and thiourea.
wherein X and Y are independently oxygen or sulfur and may be different or the same.
A most preferred (thio)epoxy compound having at least one intramolecular disulfide bond is bis(2,3-epithiopropyl) disulfide.
The (thio)epoxy compound having at least one intramolecular disulfide bond may be used to improve a refractive index of a resin prepared by curing a polymerizable composition comprising the (thio)epoxy compound.
A polymerizable composition comprising a (thio)epoxy c
Kanemura Yoshinobu
Kobayashi Seiichi
Morijiri Hiroyuki
Okazaki Koju
Ryu Akinori
Burns Doane Swecker & Mathis L.L.P.
Mitsui Chemicals Inc.
Sanders Kriellion
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