Organic compounds -- part of the class 532-570 series – Organic compounds – Isocyanate esters
Reexamination Certificate
1999-07-28
2001-02-27
Killos, Paul J. (Department: 1623)
Organic compounds -- part of the class 532-570 series
Organic compounds
Isocyanate esters
C351S159000
Reexamination Certificate
active
06194603
ABSTRACT:
BACKGROUND OF THE INVENTION
(a) Technical Field
The present invention relates to a polyisocyanate compound and a process for producing the same. More specifically, the present invention relates to a novel polyisocyanate compound useful as a starting material for an optical material which has excellent optical characteristics such as a high refractive index and low dispersion, and a process for producing the same with good efficiency.
Moreover the present invention relates to an optical material and an optical product using the same. More specifically, it relates to an optical material which has excellent optical characteristics such as high refractive index, low dispersion, excellent transparency, lack of optical distortion and the like, and which is also good in heat resistance, solvent resistance and weatherability, 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.
(b) Related Art
In comparison with glass, plastics are lightweight, hard to break, and easy to dye. Therefore, plastics have been applied, in recent years, to optical use in various lenses and the like. As optical plastic materials, polyethylene glycol bisallyl carbonate (CR-39) and polymethyl methacrylate (PMMA) have been generally used. However, these plastic materials have a refractive index of 1.50 or less. Therefore, when they are used as lens materials, for example, the thickness of the lenses has to be increased with increasing lens power. Consequently, not only is the superiority of plastics lightweight materials impaired, but thick lenses have undesirable aesthetic properties. Furthermore, concave lenses in particular have been problematic in that the thickness (edge thickness) of the surrounding portion of the lens is increased and birefringence or chromatic aberration is liable to occur.
Therefore, in order to be able to decrease the thickness of the lens, while making the most of the characteristics of plastics with low specific gravity, a plastic material having a high refractive index has been in demand. Among materials having such performance are, for example, (1) a polymer comprising a xylylene diisocyanate compound and a polythiol compound (Japanese Unexamined Patent Publication JP-A-63-46213), (2) a resin comprising an aliphatic linear sulfur-containing difunctional isocyanate and a polythiol compound (Japanese Unexamined Patent Publication JP-A-2-153302), (3) a polymer comprising an aliphatic branched sulfur-containing difunctional isocyanate compound and a polythiol compound (Japanese Unexamined Patent Publication JP-A-10-45707).
Although the above-mentioned polymer (1) and resin (2) have an increased refractive index by limiting a combination with the polythiol compound to be polymerized, problems arise such as a decreased Abbe number and increased chromatic aberration in polymer (1) and decreased heat resistance in resin (2).
Meanwhile, the above-mentioned polymer (3) has a high refractive index, and improvements in the chromatic aberration and heat resistance are found therein, but the heat resistance is not yet satisfactory, and solvent resistance is also poor.
Furthermore, since these are uncrosslinked polymers obtained from difunctional isocyanate compounds, a special crosslinking agent is needed separately to improve the heat resistance and solvent resistance. Thus, there is a problem that it is unavoidable to limit the type of the polythiol compound to be polymerized.
It is therefore an object of the present invention to provide, under these circumstances, a novel polyisocyanate compound which can give an optical material having a high refractive index, low dispersion, excellent heat resistance and excellent solvent resistance. It is also an object and to provide a process for producing this compound at good efficiency.
It is a further object of the present invention to provide, under these circumstances, an optical material which has excellent optical characteristics such as high refractive index, low dispersion, excellent transparency, lack of optical distortion and the like, and which is also good in heat resistance, solvent resistance and weatherability. It is a still further object to provide an optical product formed of this optical material.
SUMMARY OF THE INVENTION
The present inventors have assiduously conducted investigations to achieve the above-mentioned objects, and have consequently found that a polyisocyanate compound having sulfur atoms contributing to a high refractive index and a low dispersion in a main skeleton and having three isocyanate groups as polymerization functional groups is a novel compound and is adapted to the above objects, and that this compound can be obtained at good efficiency by the specific processes described herein Moreover, the inventors have consequently found that an optical material formed of a poly(thio)urethane obtained by subjecting a component containing a specific polyisocyanate compound and a component containing a compound having two or more of hydroxyl groups, or mercapto groups, or both of these groups in a molecule, to a polyaddition reaction, can be adapted to the above objects.
These findings have led to the completion of the present invention.
That is, in accordance with the above objects, the present invention provides a polyisocyanate compound represented by general formula (I)
wherein Z represents a direct bond or —CH
2
—.
Further, this polyisocyanate compound can be produced by the following processes (production processes 1 and 2) according to the present invention.
First, the production process 1 of the present invention is a process for producing a polyisocyanate compound represented by general formula (I-a)
wherein Y represents ═CH— or ═CHCH
2
—, comprising the steps of:
(a) reacting a dihalogeno-aliphatic carboxylic acid lower alkyl ester represented by general formula (II)
X
2
—Y—COOR
1
. . . (II)
wherein X represents a halogen atom, Y is as defined
above, and R
1
represents a lower alkyl group, with a thioglycolic acid lower alkyl ester to obtain a tricarboxylic acid ester represented by general formula (III)
wherein R
2
represents a lower alkyl group, and Y and
R
1
are as defined above;
(b) converting the tricarboxylic acid ester to a tricarbonyl hydrazide represented by general formula (IV)
wherein Y is as defined above; and
(c) converting one or more of the carbonyl hydrazide groups of the general formula (IV) into an isocyanate group.
Next the production process 2 of the present invention is a process for producing 1,5-diisocyanato-3-isocyanatomethyl-2,4-dithiapentane represented by formula (I-b)
comprising the steps of:
(a) reacting a propiolic acid lower alkyl ester represented by general formula (V)
CH≡C—COOR
3
. . . (V)
wherein R
3
represents a lower alkyl group, with a thioglycolic acid lower alkyl ester, to obtain a tricarboxylic acid ester represented by general formula (VI)
wherein R
2
represents a lower alkyl group, and R
3
is as defined above;
(b) converting the tricarboxylic acid ester (VI) into 1,5-bis(hydrazinocarbonyl)-3-hydrazinocarbonylmethyl-2,4-dithiapentane represented by formula (VII),
(c) converting one or more of the carbonyl hydrazide groups into isocyanate groups.
Furthermore, the present invention provides an optical material formed of or comprising a poly(thio)urethane obtained by subjecting to a polyaddition reaction a monomer mixture comprising (A) a component containing at least a polyisocyanate compound represented by general formula (I)
wherein Z represents a direct bond or —CH
2
—, and (B) a component containing at least one member selected from the group consisting of (a) a compound having two or more mercapto groups in a molecule, (b) a compound having two or more hydroxyl groups in a molecule and (c) a compound having one or more hydroxyl groups and one or more mercapto groups in a molecule.
Furthermore, the present invention provides an optical product formed of or comprising the above-mention
Jiang Jian
Kitahara Yoshitaka
Griffin & Szipl, P.C.
Hoya Corporation
Killos Paul J.
Oh Taylor V
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