Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From sulfur-containing reactant
Reexamination Certificate
1998-11-23
2001-05-01
Short, Patricia A. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From sulfur-containing reactant
C528S377000, C528S405000
Reexamination Certificate
active
06225439
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a composition which is advantageously used for optical materials, such as plastic lenses, prisms, substrates of information recording materials and filters, particularly as a material of plastic lenses of glasses.
2. Description of the Related Arts
Plastic materials have widely been used as various optical materials, particularly as lenses of glasses, because of light weight, toughness and easiness of tinting. The properties required for optical materials, particularly for lenses of glasses, are a low specific gravity, optical properties such as large refractive index and Abbe number and physical properties such as high heat resistance and strength. A large refractive index is important to decrease thickness of a lens. A large Abbe number is important to decrease the chromatic aberration of a lens. High heat resistance and strength are important to facilitate fabrication and also from the standpoint of safety.
As conventional materials having a large refractive index, thermosetting optical materials having a thiourethane structure which are obtained by the reaction of a polythiol compound and a polyisocyanate compound have been proposed (Japanese Patent Publication Heisei 4(1992)-58489 and Japanese Patent Application Laid-Open No. Heisei 5(1993)-148340). Technology to obtain a lens by polymerization of an epoxy resin or an episulfide resin with a multi-functional compound have also been proposed in the specifications of Japanese Patent Application Laid-Open No. Heisei 1(1989)-98615, Japanese Patent Application Laid-Open No. Heisei 3(1991)-81320 and International Patent Application Laid-Open No. wo8910575. Of course, optical materials having further large refractive indices are desirable.
A small chromatic aberration is another important property required for an optical material. The larger the Abbe number, the smaller the chromatic aberration. Therefore, a material having a large Abbe number is also desirable. Thus, a material having both large refractive index and large Abbe number is desired.
However, the Abbe number tends to decrease with an increase in the refractive index. Plastic materials obtained from conventional compounds have a maximum Abbe number of about 50 to 55 when the refractive index is 1.50 to 1.55, about 40 when the refractive index is 1.60 and about 31 when the refractive index is 1.66. When the refractive index is forced to increase to 1.70, the Abbe number decreases to 30 or less and the obtained material cannot practically be used.
Moreover, in the case of conventional materials, particularly materials having a thiourethane structure, the molecular weight of a sulfur-containing compound used as the raw material must be increased to achieve a large refractive index and this decreases the crosslinking density. The content of alkyl groups must be increased to achieve a large Abbe number and this decreases the rigidity of molecules of the raw material compounds. As the result, drawbacks such as a decrease in heat resistance arise. In other words, the refractive index of conventional optical materials obtained from episulfide compounds, polythiol compounds and isocyanate compounds can be increased only to a limited degree. Moreover, an increase in the refractive index decreases the Abbe number. Therefore, an advantageous balance between a large refractive index and a large Abbe number cannot be achieved by conventional optical materials.
To solve the above problems, the present inventors discovered a novel sulfur-containing compound having an episulfide structure from which an optical material having a small thickness and a decreased chromatic aberration could be obtained (Japanese Patent Application Nos. Heisei 8(1996)-214631 and Heisei 8(1996)-5797). However, the optical material obtained by curing this sulfur-containing compound by polymerization does not show a sufficient tint performance.
SUMMARY OF THE INVENTION
The present invention has an object to improve the tint performance of the resin obtained by curing by polymerization of the above novel sulfur-containing compound having the episulfide structure which has been discovered by the present inventors.
Accordingly, the present invention provides a composition for a resin which comprises:
(a) a compound having one or more structures represented by the following formula (1) in one molecule:
wherein R
1
represents a hydrocarbon group having 1 to 10 carbon atoms, R
2
, R
3
and R
4
each represents a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms, X represents S or O and an average number of S represented by X is about 50% or more of a total number of S and O constituting the three-membered ring, and
(b) a compound having one or more active hydrogen atoms in one molecule, at least one of the active hydrogen atoms being an active hydrogen atom other than the hydrogen atom of the SH group,
wherein a ratio by mol of a total of the active hydrogen atom other than the hydrogen atom of the SH group in compound (b) to a total of episulfide group and epoxy group in compound (a) is 0.001 to 0.5; and
a resin obtained by curing this composition by polymerization.
The present invention also provides a composition for a resin described above, wherein compound (a) is a compound represented by the following formula (2):
wherein R
5
to R
10
each represents a hydrogen atom or a hydrocarbon group wherein R
5
to R
10
each represents hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms, X represents S or O and an average number of S represented by X is about 50% or more of a total number of S and O constituting the three-member rings, m represents 1 to 6 and n represents 0 to 4.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In the present invention, the ratio by mol of the total of the active hydrogen atom other than the hydrogen atom of the SH group in compound (b) to the total of the episulfide group and/or the epoxy group is 0.001 to 0.5, preferably 0.001 to 0.3, more preferably 0.001 to 0.2 and most preferably 0.01 or more and less than 0.1. When the ratio exceeds 0.5, the heat resistance of the material obtained by curing the composition for a resin by polymerization decreases and the obtained material cannot be used as an optical material. When the ratio is less than 0.001, the excellent tint performance which is the object of the present invention is not obtained.
To obtain the large refractive index which is also the object of the present invention, it is preferable that R
1
in formula (1) represents a methylene group or an ethylene group and R
2
, R
3
and R
4
in formula (1) and R
5
, R
6
and R
7
in formula (2) each preferably represents a hydrogen atom or a methyl group. It is more preferable that R
1
represents a methylene group and R
2
, R
3
, R
4
, R
5
, R
6
and R
7
each represents a hydrogen atom. The average number of S in each of formula (1) and formula (2) is 50% or more, preferably 90% or more, more preferably 95% or more and most preferably substantially 100% of the total number of S and O constituting the three-membered rings.
Examples of compound (a) which is the compound having one or more structures represented by formula (1) in one molecule are as follows.
I. Examples of the compound having one structure represented by formula (1) in one molecule include bis(&bgr;-epothiopropyl)sulfide and compounds obtained by substituting at least one hydrogen atom of the episulfide group in bis(&bgr;-epothiopropyl)sulfide with a methyl group.
II. Examples of the compound having two or more structures represented by formula (1) in one molecule include:
(A) Organic compounds having a chain aliphatic backbone structure to which two or more structures represented by formula (1) are bonded.
(B) Organic compounds having a cyclic aliphatic backbone structure to which two or more structures represented by formula (1) are bonded.
(C) Organic compounds having a aromatic backbone structure to which two or more structures represented by formula (1) are bonded.
The above compounds may also contain oth
Amagai Akikazu
Mizuno Katsuyuki
Shimuta Masanori
Takeuchi Motoharu
Frishauf, Holtz Goodman, Langer & Chick, P.C.
Mitsubishi Gas Chemical Company Inc.
Short Patricia A.
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