Process for Polymerisation of Diethylene Glycol Bis Allyl Carbonate

Abstract

A process for polymerization of diethylene glycol bis allyl carbonate which may advantageously be employed for producing plastic lenses having a low refractive index comprising in the step of subjecting diethylene glycol bis allyl carbonate to the step of gamma radiation in the presence of diiso propyl peroxydicarbonate as a catalyst.

Description

FIELD OF INVENTION

This invention relates to a process for polymerization of diethylene glycol bis allyl carbonate. The polymerized carbonate may be used for lenses Having a low refractive index.

BACKGROUND OF INVENTION

Plastic ophthalmic lenses are classified by their refractive index, and the refractive index defines the power of the lens.

Hitherto, lenses having a low refractive index (1.52) was normally made by the thermal polymerization of diethylene glycol bis allyl carbonate. The process consisted in subjecting diethylene glycol bis allyl carbonate to the step of thermal polymerization in the presence of thermal initiator normally comprising diiso propyl peroxydicarbonate. Such a thermal polymerization consisted of a thermal cycle at different temperatures.

A disadvantage associated with such a known process is that of high power consumption and time consuming.

OBJECTS OF THE INVENTION

An object of this invention is to propose an improved process for polymerization of diethylene glycol bis allyl carbonate which may advantageously be used for the manufacture of opthalmic lenses of low refractive index.

Another object of this invention is to propose a process for polymerization of diethylene glycol bis allyl carbonate which avoids a high power consumption as associated with the known process.

Still another object of this invention is to propose a process for polymerization of diethylene glycol bis allyl carbonate which may advantageously be used for the manufacture of opthalmic lenses having good optical properties.

Yet another object of this invention is to propose a process for polymerization of diethylene glycol bis allyl carbonate, which is efficient.

DESCRIPTION OF INVENTION

According to this invention there is provided a process for polymerization of diethylene glycol bis allyl carbonate which may advantageously be employed for producing plastic lenses having a low refractive index comprising in the step of subjecting diethylene glycol bis allyl carbonate to the step of gamma radiation in the presence of diiso propyl peroxydicarbonate as a catalyst.

In accordance with this invention the process of polymerization comprises in the step of gamma radiation in distinction to the known process of thermal polymerization. Specifically, the present invention envisages in subjecting diethylene glycol bis allyl carbonate to the step of gamma radiation in the presence of said catalyst for a period of 8 to 10 hours and at a radiation dose of 75 to 85 KGy. If, the dose is increased to more than 85K KGy, then the lens has a yellowish colour. However, if the dose is below 75 KGy, the polymerization is incomplete.

Preferably, 1 to 1.5% of catalyst is used in the said step of polymerization.

Further objects and advantages are apparent from the ensuing examples:

EXAMPLE 1

Diethylene glycol bis allyl carbonate also known as CR-39 is taken and mixed with 1.2% of diiso propyl peroxy carbonate also known as IPP. The mixture is taken in a syringe and injected into glass blanks fitted in a gasket. The mold containing the polymerization mixture is exposed to gamma radiation of 15-85 klay.

The glass blanks turned dark known on exposure to gamma irradiation, colorless, clean and transparent lenses having a refractive index of 1.52, transmittance greater than 90% and Barcol hardness of 40 was obtained.

Claims

1-4. (canceled)

5. A method for polymerization of diethylene glycol bis allyl carbonate comprising irradiating diethylene glycol bis allyl carbonate monomer with gamma radiation in the presence of diiso propyl peroxydicarbonate as a catalyst.

6. The method as claimed in claim 5, wherein the radiation dose is 75 to 85 KGy.

7. The method as claimed in claim 5, wherein the radiation is carried out for a period of 8 to 10 hours.

8. The method as claimed in claim 5, wherein the catalyst is present in an amount of 1 to 1.5%.