RADIATION CURABLE COMPOSITIONS FOR COATING OPTICAL FIBER VIA ALTERNATIVE OLIGOMERS AND THE COATINGS PRODUCED THEREFROM
Described and claimed herein are radiation curable compositions for coating an optical fiber, particularly primary coating compositions, wherein the composition possesses specified liquid glass transition temperatures, and/or viscosity ratios between, e.g., 25° C. and 85° C. Such compositions preferably possess large amounts of a reactive oligomer component that is either not substantially derived from, or preferably substantially free from polypropylene glycol, with select diisocyanate constituents, one or more reactive diluent monomers, a photoinitiator, and optionally, one or more additives. Such compositions also are preferably sufficiently viscous at room temperature to ensure optimum optical fiber coating processability. Also described and claimed are methods of using such radiation curable compositions in high speed and/or low helium optical fiber coating applications, along with the coated optical fibers produced therefrom.
1 . A radiation curable composition for coating an optical fiber comprising:
a reactive oligomer comprising at least one polymerizable group, wherein said reactive oligomer is not substantially derived from polypropylene glycol;
a reactive diluent monomer;
a photoinitiator; and
optionally, one or more additives;
wherein the radiation curable composition possesses a liquid glass transition temperature (Tg,rheo), a first viscosity at 25° Celsius (C) (η 25 ), a second viscosity at 55° C. (η 55 ), and a third viscosity at 85° C. (η 85 );
wherein the Tg,rheo of the radiation curable composition is less than −74° C., wherein Tg, rheo is determined by fitting equation (8) to experimental viscosity versus temperature data for the radiation curable composition:
η
(
T
)
/
η
25
=
10
(
-
562.5
/
(
62.5
-
T
g
,
rheo
)
*
(
T
-
25
)
37.5
+
T
-
T
g
,
rheo
)
,
where η(T) is the viscosity (in Pa·s) of the composition at temperature, T (in ° C.).
2 . A radiation curable composition for coating an optical fiber comprising:
a reactive oligomer comprising at least one polymerizable group and a backbone, wherein the reactive oligomer comprises a urethane acrylate oligomer which is a product of reactants, said reactants comprising an isocyanate, a polyol, and an acrylate monomer;
a reactive diluent monomer;
a photoinitiator; and
optionally, one or more additives;
wherein the polyol contains a tertiary carbon content of less than 17.2 mol/kg;
wherein the radiation curable composition possesses a liquid glass transition temperature (Tg,rheo), a first viscosity at 25° Celsius (C) (η 25 ), a second viscosity at 55° C. (η 55 ), and a third viscosity at 85° C. (η 85 );
wherein the Tg,rheo of the radiation curable composition is less than −74° C., wherein Tg, rheo is determined by fitting equation (8) to experimental viscosity versus temperature data for the radiation curable composition:
η
(
T
)
/
η
25
=
10
(
-
562.5
/
(
62.5
-
T
g
,
rheo
)
*
(
T
-
25
)
37.5
+
T
-
T
g
,
rheo
)
,
where η(T) is the viscosity (in Pa·s) of the composition at temperature, T (in ° C.).
3 . The radiation curable composition according to claim 2 , wherein the composition comprises a difunctional reactive oligomer, wherein difunctional is defined as having an average between 1.5 and 2.5 reactive groups per oligomer.
4 . The radiation curable composition according to claim 2 , wherein the reactive diluent monomer comprises 2-ethylhexyl acrylate, 2-phenoxyethyl acrylate, 2-(2-ethoxyethoxy)ethyl acrylate, n-vinyl pyrrolidone, dimethylacryl-amide, n-vinylcaprolactam, ethoxylated 2-phenoxy ethyl acrylate, 4-hydroxy butyl acrylate, lauryl acrylate, isobornyl acrylate, caprolactone acrylate, ethoxylated nonylphenol acrylate, or isodecyl acrylate, or combinations thereof.
5 . The radiation curable composition according to claim 2 , wherein the reactive oligomer comprises a block copolymer, wherein the reactive oligomer possesses a monoblock structure, a diblock structure, or a triblock structure,
wherein a monoblock structure is defined as an average number from 0.9 to less than 1.5 polyether blocks per unreacted oligomer,
a diblock structure is defined as an average number of between 1.5 to less than 2.5 polyether blocks per unreacted oligomer, and
a triblock structure is defined as an average number of between 2.5 to less than 3.5 polyether blocks per unreacted oligomer.
6 . (canceled)
7 . The radiation curable composition according to claim 2 , wherein the reactive oligomer possesses a number average molecular weight, as measured by a size exclusion chromatography method calibrated against a polystyrene standard, from 7,000 to 15,000 g/mol.
8 . The radiation curable composition according to claim 2 , wherein the reactive oligomer is present by weight, relative to the weight of the entire radiation curable composition, in an amount of from 50 to 80 wt. %.
9 . The radiation curable composition according to claim 2 , wherein the radiation curable composition is a liquid at each of the first viscosity, the second viscosity, and the third viscosity, and wherein the ratio of the first viscosity to the third viscosity is less than 18.
10 . (canceled)
11 . The radiation curable composition according to claim 2 , wherein the third viscosity is from 0.01 Pa·s to 2 Pa·s.
12 . The radiation curable composition according to claim 2 , comprising a second reactive diluent monomer.
13 . The radiation curable composition according to claim 2 , wherein the reactants are present in an amount, by molar ratio of polyol groups to isocyanate groups, from 1:4 to 1:1, and by molar ratio of isocyanate groups to acrylate groups from 1.5:1 to 5:1.
14 . The radiation curable composition according to claim 2 , wherein the reactive oligomer is a copolymer which is a reaction product of reactants including multiple polyols, wherein the average tertiary carbon content of all of the multiple polyols used, by weight fraction, is from 6 mol/kg to 15 mol/kg.
15 . The radiation curable composition according to claim 2 , wherein the polyol comprises at least one polyester, polytetramethylene ether, or polyoxypropyleneglycol block.
16 . The radiation curable composition according to claim 15 , wherein the polyol consists of, or consists essentially of, polyester, polytetramethylene ether, or polyoxypropyleneglycol blocks, or combinations thereof.
17 . The radiation curable composition according to claim 2 , wherein the isocyanate comprises isophorone diisocyanate, 2,4-isomer toluene diisocyanate, 4,4′-methylenedicyclohexyl diisocyanate, 1,5-pentane diisocyanate, 2,2,4-trimethyl-hexamethylene diisocyanate, 2,4,4-trimethyl-hexamethylene diisocyanate, or hexamethylene diisocyanate, or combinations thereof.
18 . The radiation curable composition according to claim 2 , wherein the acrylate monomer comprises 2-hydroxyethyl acrylate, caprolactone acrylate, or ethoxylated nonyl-phenol acrylate.
19 . The radiation curable composition according to claim 2 , wherein the reactive oligomer is substantially free from polypropylene glycol.
20 . The radiation curable composition according to claim 2 wherein the composition comprises, relative to the entire weight of the composition:
from 50 wt. % to 82 wt. % of the reactive oligomer;
from 10 wt. % to 50 wt. % of the reactive diluent monomer;
from 1 wt. % to 5 wt. % of the photoinitiator;
and from 1 wt. % to 5 wt. % of additives.
21 . The radiation curable composition according to claim 2 , wherein the polyol contains a tertiary carbon content from 7 mol/kg to 12 mol/kg.
22 . The radiation curable composition according to claim 9 , wherein the ratio of the first viscosity to the third viscosity is from 7 to 15.
23 . A coated optical fiber comprising a primary coating, wherein the primary coating is the cured product of the radiation curable composition according to claim 2 .