Polyisocyanate compounds, process for producing the same,...

Details Polyisocyanate compounds, process for producing the same,... Polyisocyanate compounds, process for producing the same,...

1999-07-14

2001-11-06

Sergent, Rabon (Department: 1711)

Organic compounds -- part of the class 532-570 series

Organic compounds

Heterocyclic carbon compounds containing a hetero ring...

C560S330000, C560S340000, C560S343000, C560S357000

Reexamination Certificate

active

06313316

ABSTRACT:

This application is based on Japanese patent application Nos. H10-198798 and H10-198799, both filed on Jul. 14, 1998, the entire contents of which are incorporated herein by reference.
FIELD OF THE INVENTION
The invention relates to a polyisocyanate compound and a process for producing the same. In particular, it relates to a novel polyisocyanate compound useful as a starting material for an optical material, and a process for producing the same at good efficiency. It also relates to an optical material and an optical product using the same. Specifically, it relates to an optical material which has excellent optical characteristics such as a high refractive index, a low dispersion, an excellent transparency, lack of optical distortion and the like and good heat resistance, and to an optical product formed of this optical material, such as a lens, a prism, optical fibers, a substrate for a recording medium, a filter, a glass, a vase and the like.
BACKGROUND OF THE INVENTION
Recently, plastic materials have been used for optical parts in place of inorganic glass, especially for eyeglass lenses, because they are lightweight and have good dyeability and good impact resistance. In particular, a polyethylene glycol bisallylcarbonate polymer (hereinafter referred to as CR-39) and polymethyl methacrylate (PMMA) have been used, primarily for plastic lenses. However, it has a refractive index of 1.50, which is lower than that of inorganic glass. Therefore, when they are used as lens materials, for example, the thickness of the lenses has to be increased with the increasing power. Consequently, not only is the superiority of plastics as lightweight material been impaired, but also they have not been preferred in view of the aesthetic property. Furthermore, the concave lens, in particular, has had problems when the thickness (edge thickness) of the surrounding portion of the lens is increased causing a birefringence or a chromatic aberration to occur.
For these reasons, in order to be able to decrease the thickness of the lens while applying most of the characteristics of plastics having a low specific gravity, a plastic material having a high refractive index has been in demand. As a material having such a performance, for example, (1) a polymer comprising a xylene diisocyanate compound and a polythiol compound (official gazette of JP-A-63-46213), (2) a resin comprising an aliphatic linear sulfur-containing diisocyanate and a polythiol compound (official gazette of JP-A-2-153302), (3) a polymer comprising a dithian derivative substituted with two isocyanatoalkyl groups and a polythiol (official gazette of JP-A-4-159275) are disclosed.
Although the resin in the above-mentioned item (1) and the resin in the above-mentioned item (2) have an increased refractive index by limiting a combination with a polythiol compound to be polymerized, the resin of item (1) has problems in that an Abbe number is decreased and a chromatic aberration is increased, and the resin of item (2) has a problem in that its heat resistance is decreased.
The polymer of item (3) has a high refractive index and a low dispersion (high Abbe number) and has an excellent heat resistance. However, in recent years, there has been a demand for a material having a higher refractive index and a lower dispersion.
SUMMARY OF THE INVENTION
In order to overcome many of the problems in the prior art, the invention provides an optical material having the above-mentioned desirable properties. It is a feature of the invention to provide a novel polyisocyanate compound which can give an optical material having a high refractive index, a low dispersion and an excellent heat resistance, and a process for producing this compound at good efficiency. It is also a feature of the invention to provide an optical material which has excellent optical characteristics such as a high refractive index, a low dispersion, an excellent transparency, lack of optical distortion and the like, and which has good heat resistance. It is also a feature of the invention to provide optical products made from the optical material.
In particular, the invention provides a polyisocyanate compound having a 1,4-dithian ring and an isocyanate group in a side chain connected by a sulfur atom. The compound exhibits a high refractive index, a low dispersion and high heat resistance. In addition, the invention provides methods for producing the polyisocyanate compound by an efficient processes. It also provides an optical material formed of a poly(thio)urethane obtained by subjecting a component comprising a polyisocyanate compound and a component comprising a compound having two or more of hydroxyl groups or mercapto or both groups to a polyaddition reaction.
In one aspect, the invention provides a polyisocyanate compound having general formula (I)
wherein X and Y, independently represent an alkylene group having from 1 to 5 carbon atoms or an alkylene group having from 1 to 5 carbon atoms to which group an isocyanatoalkyl group (in which the carbon number of the alkyl group is preferably between 1 and 3) is bound, these alkylene groups may have a sulfur atom, and m and n, independently represent an integer from 1 to 3.
In another embodiment, the polyisocyanate compound can be produced by one of the following processes: production process 1 and production process 2.
Production process 1 of the invention is a process for producing a polyisocyanate compound represented by general formula (I-a)
wherein m and n, independently represent an integer from 1 to 3, X
1
and Y
1
, independently represent an alkylene group having from 1 to 5 carbon atoms, and this alkylene group may have a sulfur atom.
Process 1 comprises:
(a) obtaining a dicarboxylic acid ester from a 2,5-bis(mercaptoalkyl)-1,4-dithian compound, said dicarboxylic acid being represented by general formula (III)
 wherein R
1
and R
2
, independently represent a lower alkyl group, X
1
, Y
1
, m and n are as defined above, said 2,5-bis(mercaptoalkyl)-1,4-dithian compound being represented by general formula (II)
 wherein m and n are as defined above,
(b) converting the dicarboxylic acid ester to a dicarbonyl hydrazide represented by general formula (IV)
 wherein m, n, X
1
and Y
1
are as defined above, and
(c) converting the carbonyl hydrazide group into an isocyanate group.
Production process 2 of the invention is a process for producing a polyisocyanate compound represented by general formula (I-b)
wherein A
1
and A
2
, independently represent a substituted alkylene group having from 1 to 5 carbon atoms, this alkylene group may have a sulfur atom, B
1
and B
2
, independently represent an alkylene group having from 1 to 3 carbon atoms, m and n, independently represent an integer from 1 to 3, and k represents 0 or 1.
In one aspect, the invention provides a process for producing the polyisocyanate compound of general formula (I-b), wherein said A
1
and said A
2
are each a substituted methylene group, a substituted ethylene group having said B
1
or said B
2
bound to a carbon atom bound to a sulfur atom or a substituted ethylene group having said B
1
or said B
2
bound to a carbon atom not bound to a sulfur atom, and said B
1
and said B
2
are each a methylene group.
Process 2 comprises:
(a) obtaining a tricarboxylic acid ester or a tetracarboxylic acid ester from a 2,5-bis(mercaptoalkyl)-1,4-dithian compound, the tricarboxylic acid ester or the tetracarboxylic acid ester being represented by general formula (V)
 wherein A
1
, A
2
, B
1
, B
2
, k, m and n are as defined above, and R
3
and R
4
, independently represent a lower alkyl group, the 2,5-bis(mercaptoalkyl)-1,4-dithian compound being represented by the above-mentioned general formula (II),
(b) converting the tricarboxylic acid ester or a tetracarboxylic acid ester to a tricarbonyl hydrazide or a tetracarbonyl hydrazide represented by general formula (VI)
 wherein A
1
, A
2
, B
1
, B
2
, m, n and k are as defined above, and
(c) converting the carbonyl hydrazide group into an isocyanate group.
In another embodiment, the opti

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