Polymerization catalyst for polythiourethane optical material, polymerizable composition containing the same, polythiourethane resin obtained from the composition, and process for producing the resin

Abstract

By using an amine hydrochloride represented by the formula (1) as a catalyst, a polythiourethane resin which is suitably used for a transparent resin for optical use, can be obtained without using an organotin compound which has been conventionally used as a catalyst for polythiourethane resins and without being affected by the acidity of an additive:wherein R1, R2 and R3 independently represent a monovalent or higher valent linear aliphatic, branched aliphatic, cyclic aliphatic or aromatic organic residue which may have a hydroxyl group or an amino group; and R1, R2 and R3 may be arbitrarily bonded to each other to form a ring.

Description

TECHNICAL FIELD[0001]The present invention relates to a polymerization catalyst for polythiourethane, a polymerizable composition for obtaining a polythiourethane resin, an optical material comprising the polythiourethane resin, and a process for producing the polythiourethane resin.BACKGROUND ART[0002]In recent years, harmony with global environment or reduction of environmental burdens is becoming a major issue in the industry. Therefore, the development of environmentally friendly products or technologies is accelerating. This movement is seen in a technical field of the present invention. In particular, an organotin catalyst, which is widely used as a catalyst for a polythiourethane resin, has been concerned because it is harmful to humans as it is highly toxic, may become the endocrine disrupter, etc. Consequently, regulation on the use of organotin compounds has been strengthened primarily in developed countries. In a spectacle lens industry employing polythiourethane resins, ...

AI Technical Summary

Benefits of technology

[0009]Generally a cast polymerization method, in which a polymerizable composition is injected in a mold and cured under heating, is employed for production of the polythiourethane resin as a material for plastic lenses or the like. On the occasion, the polymerization reaction is carried out from several hours to several tens of hours while gradually rising the temperature from low temperature to high temperature. It is important to ensure sufficient time until casting, that is, sufficient pot life (usable time) for the improvement of workability. In addition, it is necessary that the polymerization is completed to bring out full resin properties. In order to be completed the polymerization, examples of the method may include using a catalyst having strong polymerization activity, and increasing the amount of a catalyst. Furthermore, in order to obtain stable polymerization properties, it is important to ensure stable pot life in different lots. If the pot life fluctuates with respect to each lot, there is a possibility of affecting the quality stability of the resin by polymerization lag. Accordingly, the present invention further provides a polymerization catalyst which brings stable pot life.

[0024]A polymerization catalyst of the present invention does not contain an organotin compound possibly harmful to humans, and exhibits stable polymerization activity which is not affected by the acidity of an additive. That is, according to the present invention, since the polymerization catalyst is hardly affected by additives, quality of monomers, kinds of monomers or the like, a polymerizable composition containing the polymerization catalyst exhibits stable polymerization properties and stable pot life. The polymerization catalyst of the present invention can suppress the rate of occurrence of optical inhomogeneity or white turbidity in the obtained resin. Such a polythiourethane polymerization catalyst is suitable for application to optical materials in which high refractive index and high transparency are required.

Problems solved by technology

As a result, optical inhomogeneity or white turbidity occurred in the obtained resin in some cases, a resin having stable quality as a transparent resin for optical use such as plastic lenses for spectacles could not be always obtained.

If the pot life fluctuates with respect to each lot, there is a possibility of affecting the quality stability of the resin by polymerization lag.

Generally, optical inhomogeneity could occur in a lens when the polymerization rate is too fast, and alternatively white turbidity appears in a resin when the polymerization rate becomes slow.

A different of the polymerization rate, which occurs by the difference of the acidity of an additive, is expected to be the cause that stable resins cannot be obtained.

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