Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From sulfur-containing reactant
Reexamination Certificate
2001-07-30
2003-11-11
Truong, Duc (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From sulfur-containing reactant
C528S373000, C525S328500, C525S535000
Reexamination Certificate
active
06646104
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method of preparing a sulfur-containing compound having at least one thio group in the molecules by reacting a thiol compound with an organic compound having at least one functional group capable of forming a thio group in the molecules upon the reaction with a mercapto group, easily, in a high yield and in a highly pure form being colored little. The invention further relates to a sulfur-containing compound of a highly pure form obtained by the above method.
It is expected that the sulfur-containing compound having a thio group in the molecules can be used as an optical material that exhibits a high refractive index owing to its relatively large molecular refraction possessed by a sulfur atom and can be used in the field of medicines and agricultural chemicals owing to a high degree of activity exhibited by sulfur for animals and plants. In particular, the sulfur-containing compound is very useful as a polymerizable monomer or an intermediate product thereof for obtaining an optical material in a field where a high degree of refractive index is desired as represented by photochromic plastic lenses.
BACKGROUND ART
In the field of plastic lenses in recent years, attention has been given to those highly functional materials to which photochromic properties are imparted. Photochromic property is a reversible action of a material which quickly changes its color when irradiated with light containing ultraviolet rays such as of sunlight or light of a mercury lamp, and exhibits its initial color when the material is no longer irradiated with light but is placed in a dark place. A photochromic plastic lens is obtained by dispersing a photochromic compound having the above-mentioned property in a plastic lens. As the polymerization-curable compositions for obtaining the photochromic plastic lenses, there have been known photochromic curable compositions obtained by dissolving a photochromic compound in a radically polymerizable monomer as disclosed in Japanese Unexamined Patent Publication (Kokai) No. 124790/1991 and PCT International Patent Application No. 96/19741.
It has further been demanded to produce plastic lenses having smaller thicknesses. For example, the cured products obtained by curing the above-mentioned photochromic curable composition exhibit refractive indexes of smaller than 1.55, and it has been desired to further increase the refractive index from the standpoint of producing stronger lenses yet having smaller thicknesses.
It has generally known that a resin that exhibits a high refractive index can be realized by introducing halogen atoms other than fluorine, or by introducing aromatic rings or sulfur atoms in large amounts into the molecules of the polymerizable monomer. Among these methods, the method of introducing sulfur atoms into the monomer molecules is particularly effective from such a standpoint that the weight of the polymer (i.e., plastic lens) does not increase compared to the case of introducing halogen atoms other than fluorine or introducing aromatic rings and, besides, Abbe's number does not decrease.
When sulfur atoms are introduced into the molecules of the polymerizable compound, however, offensive odor is in many cases produced in working the finally obtained polymer (plastic lens). Besides, sulfur atoms must be introduced in large amounts from the standpoint of increasing the refractive index. Because of these reasons, there has not yet been obtained a highly refractive photochromic plastic lens which is satisfactory to a sufficient degree by using sulfur-containing polymerizable monomers.
As described above, no photochromic plastic lens has ever been known which is highly refractive, light in weight and exhibiting a large Abbe's number. It has therefore been desired to develop a method of preparing a polymerizable monomer for forming such a photochromic plastic lens maintaining a high yield and a high purity.
The present inventors have studied the method of introducing thio groups into the molecules of a polymerizable monomer based on such an idea that sulfur atoms can be introduced in large amounts into the monomer molecules by introducing sulfur atoms in the form of thio groups and that the refractive index of a polymer can be increased due to this effect.
Concerning the method of introducing thio groups into the molecules, Journal of American Chemical Society, 74, 828, 1952 teaches that an ethylphenylthio ether is obtained maintaining an yield of 82% by reacting a thiophenol with an ethyl bromide in the presence of sodium. The present inventors have attempted to synthesize a polymerizable sulfur-containing compound having thio groups relying on the sulfide-forming reaction by removing hydrogen halide by using an organohalide and metal sodium in compliance with the above-mentioned method only, however, to find that the reaction yield was from 70 to 80% involving much problem if the method is to be put into practice on an industrial scale.
According to the above method, further, use of metal sodium makes the operation cumbersome. In order to improve operability, therefore, the reaction was conducted by using an aqueous solution of sodium hydroxide instead of sodium. As a result, though the operability was improved, by-products were formed due to side reactions and, hence, the purity was low and, besides, color was observed.
Further, the polymerizable sulfur-containing compound obtained by the above method was evaluated for its performance as a monomer for producing photochromic plastic lenses. As a result, though the refractive index could be increased, there occurred a new problem in that the light resistance of photochromic properties was markedly deteriorated.
DISCLOSURE OF THE INVENTION
It is therefore an object of the present invention to provide a method of preparing a sulfur-containing compound having a thio group in the molecules by reacting a thiol compound with an organic halogen compound in the presence of a basic compound such as sodium hydroxide, the method requiring easy operation, featuring a high reaction yield of the object compound and free from the problem of coloring caused by impurities.
The invention further has an object of providing a method of preparing the sulfur-containing compound, wherein when the sulfur-containing compound having a polymerizable functional group is used as a monomer for forming the photochromic plastic lens, photochromic property having good light resistance is exhibited.
The present invention was proposed in order to solve the above-mentioned objects and was completed based on a discovery that a sulfur-containing compound which is an object compound is obtained suppressing the formation of impurities, suppressing the development of color in the product, maintaining a high purity and a high yield by controlling the amount of water in the reaction system to be smaller than a predetermined value, and that, in addition to the above, when the above reaction is conducted in an atmosphere without substantially containing oxygen such as nitrogen atmosphere, formation of the disulfide compounds, which are the impurities, is suppressed to a high degree, the disulfide compounds exhibiting chemical and physical behaviors resembling to those of the object sulfur-containing compound and, as a result, light resistance of the photochromic property is markedly improved when the above sulfur-containing compound is used as the monomer for forming photochromic plastic lenses.
That is, the present invention is concerned with a method of preparing a sulfur-containing compound having at least one thio group in the molecules by reacting a thiol compound with an organic compound having at least one functional group capable of forming a thio group in the molecules upon reacting with a mercapto group in the presence of a basic compound, wherein the number of moles of water contained in the reaction system is set to be not larger than 7.5 times as large as the number of moles obtained by multiplying the number of moles of the thiol compound to be reacted by a nu
Hara Tadashi
Momoda Junji
Mori Katsuhiro
Sherman & Shalloway
Tokuyama Corporation
Truong Duc
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