Coating of fiber lightguides with UV cured polymerization products

DETAILED DESCRIPTION The FIGURE shows a preform 10 being drawn into an endless glass fiber 11 with the aid of a heat source 12 applied in a conventional way.
A coating vessel 13 is arranged to coat the fiber with a fluid 14 which later, upon curing, becomes the protective coating for the fiber.
The coating vessel is shown here as a simple cup with a flooded exit capillary, through which the fiber is threaded.
A more detailed account of a suitable coating apparatus appears in U.
S.
patent application, Ser.
No.
600,280, filed July 31, 1975, by R.
V.
Albarino and S.
Torza, now U.
S.
Pat.
No.
4,073,974.
The fiber exiting from the coating vessel and carrying uncured resin, passes through the curing stage, which is shown here as one or more UV lamps 15 arranged with UV light incident efficiently on the fiber.
The finished fiber, now coated with a cured resin, is taken up on conventional reel 16.
The material contained in the coating vessel is, according to the invention, a prepolymer made by mixing certain epoxy resins and reacting the mixture with acrylic and/or methacrylic acid.
The mixture contains an aliphatic type glycidyl ether and an aromatic type glycidyl ether.
Excellent results have been obtained with a mixture of 1, 4-butanediol diglycidyl ether and a diglycidyl ether of bisphenol A or substituted, e.
g.
, halogenated, bisphenol A, and specifically with brominated bisphenol A.
The recommended proportion of aliphatic diglycidyl ether to aromatic diglycidyl ether is 0.
4 to 1.
0 on a weight ratio basis.
The epoxy resin mixture is reacted with acrylic and/or methacrylic acid on an equivalent basis with between 0.
5 to 1.
0 mol acid per epoxy equivalent weight, and preferably 0.
8-0.
95 mol acid per equivalent weight.
Either acrylic acid or methacrylic acid function adequately and can be mixed in any proportion to give the recommended molar quantity.
The reaction to form the prepolymer proceeds more effectively in the presence of a tertiary amine.
The amine functions as a catalyst to the epoxy-acrylic acid addition reaction