Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From sulfur-containing reactant
Reexamination Certificate
2001-10-26
2003-05-06
Truong, Duc (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From sulfur-containing reactant
C528S375000, C528S373000
Reexamination Certificate
active
06559276
ABSTRACT:
The present invention relates to an optical product such as plastic lenses, prisms, optical fibers, substrates for information recording, IR-absorbing filters, color filters and others. These optical products are made from a polymer obtained by using an asymmetric disulfide compound as an essential monomer component.
The present invention also relates to novel asymmetric disulfide compounds and to a method for producing the same. The novel asymmetric disulfide compounds are useful as a starting material for optical materials having a high refractive index and a high Abbe's number.
BACKGROUND OF THE INVENTION
Plastics are used for various optical applications these days, for example, for lenses and others, as being lightweight, hardly broken and easily colored when compared with glass. For optical plastic materials, generally used are poly(diethylene glycol bisallyl carbonate) (CR-39) and poly(methyl methacrylate). However, these plastics have a refractive index of at most 1.50. Therefore, for example, when they are used for lens materials, the lenses produced become thicker with the increase in their power, and they lose the advantage of plastics that are lightweight. In particular, powerful concave lenses are thick at their periphery, and are therefore unfavorable as causing birefringence and chromatic aberration. For spectacles, in addition, such thick lenses are often not aesthetic. For obtaining thin lenses, it is effective to increase the refractive index of the materials for them. In general, the Abbe's number of glass and plastics decreases with the increase in their refractive index, and, as a result, their chromatic aberration increases. Accordingly, desired are plastic materials having a high refractive index and a high Abbe's number.
For plastic materials having such properties, for example, (1) polyurethanes obtained through addition-polymerization of a polyol having bromine in the molecule and a polyisocyanate (Japanese Patent Laid-Open No. 164615/1983); and (2) polythiourethanes obtained through addition-polymerization of a polythiol and a polyisocyanate (Japanese Patent Publication Nos. 58489/1992 and 148340/1993), are proposed. For the starting material, polythiol for the polythiourethanes of above (2), specifically proposed are branched polythiols having an increased sulfur atom content (Japanese Patent Laid-Open Nos. 270859/1990 and 148340/1993), and polythiols into which is introduced a dithian structure for increasing their sulfur atom content (Japanese Patent Publication No. 5323/1994 and Japanese Patent Laid-Open No. 118390/1995). Further proposed are (3) polymers of an alkyl sulfide having a polymerization-functional group, episulfide (Japanese Patent Laid-Open Nos. 71580/1997 and 110979/1997).
However, though their refractive index is increased a little, the polyurethanes of above (1) still have a low Abbe's number and have some other drawbacks in that their light fastness is poor, their specific gravity is high and therefore they are not lightweight. Of the polythiourethanes (2), those for which the starting polythiol used has a high sulfur content have an increased refractive index ranging from approximately 1.60 to 1.68, but their Abbe's number is lower than that of optical inorganic glass having a refractive index on the same level. Therefore, they still have a problem in that their Abbe's number must be increased more. On the other hand, one example of the alkyl sulfide polymers (3) having an Abbe's number of 36 has an increased refractive index of 1.70. The lenses made of such polymer can be made extremely thin and lightweight. However, still desired are plastic materials of which both the Abbe's number and the refractive index are more increased.
BRIEF SUMMARY OF THE INVENTION
The present invention provides an optical product made of optical material having a high refractive index and a high Abbe's number and having superior heat resistance, superior weather resistance and superior transparency. The invention also provides novel asymmetric disulfide compounds capable of giving optical materials of which both the refractive index and the Abbe's number are high and which have superior heat resistance, superior weather resistance and superior transparency, and provides an efficient method for producing the compounds.
DETAILED DESCRIPTION OF THE INVENTION
The invention provides an optical product comprising a polymer obtained by using at least one asymmetric disulfide compound as an essential monomer component. Preferably, the asymmetric disulfide compound is one obtained through reaction of (A) an O-alkyl-S-substituted sulfenylthiocarbonate with (B) a thiol.
The component (A), O-alkyl-S-substituted sulfenylthiocarbonate may be one obtained through reaction of an alkoxycarbonylsulfenyl halide (for example, a chloride) with a thiol that differs from the thiol for the component (B) Preferred examples of the substituent for the S-substitution in the compound are hydrocarbon groups, including, for example, an alkyl group, an alkenyl group (a vinyl group, etc.), an alkynyl group (a propargyl group, etc.), etc.
The asymmetric disulfide compound may be produced via the O-alkyl-S-substituted sulfenylthiocarbonate through reaction of an alkoxycarbonylsulfenyl halide with two different types of thiols, as in the following reaction schemes (1) and (2).
In the above schemes, R
1
represents an alkyl group (e.g., a lower alkyl group, preferably a methyl group, an ethyl group, etc.); R
2
represents a thiol residue; and R
3
represents a thiol residue that differs from R
2
.
For the two different types of thiols, various thiols can be used. For example, when the thiol used for synthesizing the component (A) is 1,2-dimercaptoethane, 1,2,3-trimercaptopropane, trimercaptomethane or dimercaptomethane, the thiol of the component (B) is preferably 2,3-epithiopropylmercaptan; and when the thiol used for synthesizing the component (A) is vinylmercaptan, propargylmercaptan or 2,3-epithiopropylmercaptan, the thiol of the component (B) is preferably 1,2-dimercaptoethane, 1,2,3-trimercaptopropane, trimercaptomethane or dimercaptomethane.
The reaction in the reaction scheme (1) is carried out in a solvent (e.g., dichloromethane) at 0 to −78° C. for 1 to 12 hours with dehydrochlorination. The resulting O-alkyl-S-substituted sulfenylthiocarbonate is, after optionally isolated and purified, then mixed with a pure thiol in the presence of from 10
−6
to 10
−3
mol % of an amine catalyst with stirring, according to the reaction scheme (2), to obtain the intended asymmetric disulfide of the invention.
The production method may be described as follows. Specifically, even though the thiol R
2
SH to constitute a part of the asymmetric disulfide compound is unstable at ambient temperature under atmospheric pressure, it is reacted with an alkoxycarbonylsulfenyl halide to give a stable O-alkyl-S-substituted sulfenylthiocarbonate having the structure of the thiol R
2
SH introduced thereinto, which can be stored at ambient temperature under atmospheric pressure. The reaction goes well even at relatively low temperatures at which the thiol is stable.
In addition, the reaction of the O-alkyl-S-substituted sulfenylthiocarbonate with the other thiol R
3
SH (the reaction according to the reaction scheme (2)) goes quantitatively, and gives the intended asymmetric disulfide that is substantially colorless and pure. The by-products, carbonyl sulfide and alkyl alcohol R
1
OH, are both volatile, and can be readily removed under reduced pressure.
Accordingly, an asymmetric disulfide not requiring purification is obtained from the pure O-alkyl-S-substituted sulfenylthiocarbonate and a thiol. In case where the intended asymmetric disulfide is difficult to purify or where less colored optical materials are desired to be obtained, this production method is useful.
In the alkoxycarbonylsulfenyl halide to be used in the first reaction, the alkoxy group is preferably a methoxy group or an ethoxy group for enabling easy removal of the alcoh
Jiang Jian
Okubo Tsuyoshi
Hoya Corporation
Truong Duc
LandOfFree
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