Low-volatility radiation-curable composition for coating an optical fiber

Abstract

Disclosed and claimed herein are one or more oligomers (a) that are reaction products of a hydroxy-functional or thiol-functional backbone compound, an isocyanate compound, and a hydroxyl-functional endcapper, optionally one or more second oligomers (b), optionally one or more reactive diluent monomers, one or more photoinitiators, and optionally one or more additives, which is a primary optical fiber coating composition. The oligomers are present in an amount of at least 0.01% by weight based on the total coating composition, and the molar ratio of isocyanate groups to hydroxyl or thiol groups is 1.0 or less. The total amount of (a)+(b) is between 70% and 99% by weight. Also disclosed are a method of coating an optical fiber incorporating the composition described herein, and a coated optical fiber and cable produced therefrom.

Description

Technical Field

[0001] The present invention generally relates to a radiation-curable formulation particularly suitable as an optical fiber primary coating composition, a method of coating an optical fiber using the radiation-curable formulation as a primary coating composition, and a coated optical fiber produced therefrom. Cross-reference to related applications

[0002] None

Background Art

[0003] An optical fiber is composed of a glass fiber obtained by thermal melting spinning of glass and one or more coating layers disposed on the glass fiber for protection and reinforcement. Optical fibers are produced, for example, by first forming a flexible primary coating layer on the surface of the glass fiber and then forming a more rigid secondary coating layer called a secondary coating on the primary coating. Also known are tape-like optical fibers or optical fiber cables having a plurality of optical fibers with coating layers bonded together with a binder.

[0004] Radiation-curable thermosetting compositions have been used for a long time to form primary and secondary coating layers because they are particularly fast-curing and can impart desired properties to optical fibers. Typically, a radiation-curable optical fiber coating is a cured product of a composition containing a mixture of one or more components having one or more ethylenically unsaturated (C═C) bonds that undergo crosslinking by free radical polymerization under the influence of irradiation. Such compositions usually also contain a photoinitiator to assist in radiation curing, particularly when curing is effected by irradiation with ultraviolet (UV) wavelengths.

[0005] The relatively soft inner primary coating provides resistance to unwanted microbending, which results in further attenuation (i.e., signal loss) of signal transmission in the coated optical fiber. Microbends are microscopic curvatures in the optical fiber that include local axial displacements of a few micrometers and spatial wavelengths of a few millimeters. Microbends can be induced by thermal stress and / or mechanical lateral forces. The coating can provide protection against lateral forces that protect the optical fiber from microbending, but the amount of protection provided decreases as the thickness of the coating decreases.

[0006] The primary coating preferably has a higher refractive index than the cladding of the associated optical fiber so as to be able to remove spurious optical signals from the core of the optical fiber. The primary coating should maintain adequate adhesion to the glass fiber during heat and hydrolysis aging, but can be peelable from the glass fiber for splicing purposes (if desired). The primary coating typically has a thickness in the range of 20 to 50 μm (e.g., about 25 or 32.5 μm), and for a 200 μm fiber, has a thinner thickness in the range of 15 to 25 μm.

[0007] The harder secondary coating provides resistance to handling forces such as occur when the coated optical fiber is ribbonized and / or cabled. The secondary coating composition of a radiation-curable optical fiber also generally includes a mixture of ethylenically unsaturated compounds and one or more acrylate-functional oligomers and photoinitiators dissolved or dispersed in a liquid ethylenically unsaturated diluent. The coating composition is typically applied to the optical fiber in liquid form and then exposed to actinic radiation to effect curing.

[0008] A method commonly used to form a coating layer on a glass fiber is, for example, to coat the glass fiber with a liquid curable resin composition and cure it with heat or light, particularly ultraviolet light. The optical fiber coating including the primary layer and the secondary layer is typically applied using one of two processes, namely, wet-on-wet (WOW) and wet-on-dry (WOD). In the WOD process, the fiber first passes through a primary coating application that is cured by exposure to UV radiation. The fiber then passes through a secondary coating application and is subsequently cured by similar means. In the WOW process, the fiber passes through both the primary and secondary coating applications, and then the fiber proceeds to the curing step. In the wet-on-wet process, the curing lamp between the primary coating and the secondary coating is omitted. Summary of the Invention Problems to be Solved by the Invention

[0009] There continues to be a movement towards more sustainable and effective optical fiber coatings. Known optical fiber coatings that cure fast enough, impart sufficient performance on the fiber, and still adhere well to the optical fiber substrates to which they are related still have room for improvement. Specifically, it is desirable to provide an optical fiber primary coating that maintains an acceptable curing rate and performance on the fiber, yet has lower volatility, as evidenced by a reduction in the content of monomer and / or diluent compounds contained therein, as expected by the industry. [Brief Description of the Drawings]

[0010] None Means for Solving the Problems

[0011] This specification describes several aspects and embodiments of the present invention. A first aspect is, based on the weight of the entire primary coating composition: (a) at least 0.01% by weight of one or more oligomers that are reaction products of (i) a hydroxy-functional or thiol-functional backbone compound, (ii) an isocyanate compound; and (iii) a hydroxyl-functional endcapper further containing an ethylenically unsaturated moiety, wherein the molar ratio of the number of isocyanate groups in (ii) to the number of hydroxyl and thiol groups in (i) is 1.0 or less; (b) optionally, one or more urethane (meth)acrylate oligomers other than (a); (c) optionally, a reactive diluent monomer; (d) a photoinitiator; (e) optionally, one or more additives; wherein the total amount of (a)+(b) is 70% to 99% by weight, and it is an optical fiber primary coating composition. When (b) is absent, the one or more oligomers described in (a) preferably have at least two ethylenically unsaturated groups. More preferably, when (b) is absent, the one or more oligomers described in (a) have two ethylenically unsaturated groups.

[0012] In another embodiment according to the first aspect, the one or more oligomers described in (a) are present in the optical fiber primary coating composition in an amount of more than 0.1% by weight, preferably more than 1% by weight, preferably more than 5% by weight, preferably more than 10% by weight, preferably more than 40% by weight, and preferably 96% by weight or less, more preferably 95% by weight or less, more preferably 90% by weight or less, more preferably 80% by weight or less, more preferably 70% by weight or less. In yet another embodiment, the molar ratio of the number of isocyanate groups in (ii) to the number of hydroxyl and thiol groups in (i) is 2 / 3 (about 0.67) or more, such that it is between 2 / 3 and 1.0. In various other embodiments of the first aspect, the one or more oligomers described in (a) have various urethane linkages, block structures, theoretical molecular weight values, terminal portions, backbone types, isocyanate types, and hydroxyl-functional endcap types. In yet another embodiment, more specific types regarding elements (b)-(e) are described.

[0013] The second aspect of the present invention is a method for coating an optical fiber, comprising the steps of: providing a glass optical fiber, preferably by drawing the glass optical fiber through a drawing tower; applying a primary coating composition onto the surface of the glass optical fiber; optionally, applying a dose of UV light sufficient to at least partially cure the primary coating composition; applying a secondary coating composition onto the primary coating composition; and exposing the primary coating composition and the secondary coating composition to at least one radiation source capable of emitting ultraviolet light and affecting the curing of the primary coating composition and the secondary coating composition to form a cured primary coating on the surface of the optical fiber and a cured secondary coating on the surface of the cured primary coating; wherein the primary coating composition is a composition according to any of the embodiments of the first aspect of the present invention.

[0014] The third aspect of the present invention is a coated optical fiber, comprising a glass core and a cladding layer in contact with and surrounding the glass core; and a coated portion further comprising a primary coating layer in contact with and surrounding the cladding layer; and a secondary coating layer in contact with and surrounding the primary coating layer. According to this third aspect, the primary coating layer is a cured product of a radiation-curable composition according to any of the embodiments of the first aspect, and the primary coating and the secondary coating are applied and cured according to any of the embodiments of the second aspect. **DETAILED DESCRIPTION OF THE INVENTION**

[0015] The first aspect of the present invention is, with respect to the total weight of the primary coating composition: (a) One or more oligomers that are reaction products of at least 0.01% by weight of (i) a hydroxy-functional or thiol-functional main chain compound, (ii) an isocyanate compound, and (iii) a hydroxyl-functional end capper further containing an ethylenically unsaturated moiety, wherein the molar ratio of the number of isocyanate groups in (ii) to the number of hydroxyl and thiol groups in (i) is 1.0 or less; (b) Optionally, one or more urethane (meth)acrylate oligomers other than (a); (c) Optionally, a reactive diluent monomer; (d) A photoinitiator; (e) Optionally, one or more additives comprising, or consisting essentially of, or consisting of, a radiation-curable composition for coating an optical fiber, wherein the total amount of (a) + (b) is 70% to 99% by weight. When (b) is absent, the one or more oligomers described in (a) preferably have at least two ethylenically unsaturated groups. More preferably, when (b) is absent, the one or more oligomers described in (a) have two ethylenically unsaturated groups.

[0016] Accordingly, a radiation-curable composition for coating an optical fiber according to a first aspect of the present invention may contain an oligomer (a), a second oligomer (b), a reactive diluent component (c), a photoinitiator component (d), and an additive component (e). Such components described below can be used in a composition or formulation according to any aspect of the present invention, including the primary coating composition for an optical fiber according to the first aspect, the primary coating composition used in a method for coating an optical fiber according to the second aspect, and the composition coated and cured on an optical fiber described in connection with the third aspect.

[0017] Surprisingly, oligomer (a) has been found to tend to have a lower viscosity value. Surprisingly, the presence of such an oligomer in the optical fiber primary coating composition beneficially contributes to the ability to reduce the volatile content of the optical fiber primary coating composition while remaining suitable for use in optical fiber coating applications, and in particular, it has been found to maintain an acceptable viscosity and curing rate as well as performance on the fiber, as expected by the industry. Oligomer component

[0018] The radiation curable composition according to the present invention comprises an oligomer component; that is, a collection of one or more individual oligomers having one or more specific structures or types. Oligomers are used herein to mean molecules of intermediate relative molecular weight, the structure of which includes, actually or conceptually, a plurality of units derived from molecules of lower relative molecular weight. As used herein, a component is considered an oligomer if it further has a number average molecular weight (Mn) greater than about 1 kilodalton (kDa), as measured preferably by the size exclusion chromatography (SEC) method described elsewhere herein. It will be understood by those skilled in the art that oligomers having Mn values in this range are generally less volatile than their low molecular weight analogs and, therefore, advantageously have a low likelihood of migrating from the primary coating composition to the glass tube surrounding the optical fiber during the drawing process.

[0019] In one embodiment, the oligomer component comprises, consists of, or consists essentially of one or more oligomers having an Mn of at least 1 kilodalton (kDa), or at least 2 kDa, or at least 3 kDa, or at least 5 kDa, or at least 10 kDa, or at least 20 kDa, or at least 30 kDa, or at least 40 kDa, or from 20 to 150 kDa, or from 20 to 130 kDa, or from 20 to 100 kDa, or from 30 to 80 kDa, or from 35 to 55 kDa. According to other embodiments, the oligomer component comprises, consists of, or consists essentially of one or more oligomers having a theoretical molecular weight (Mn, theo) of at least 1 kDa, or at least 5 kDa, or at least 10 kilodaltons (kDa), more preferably greater than 12 kDa, more preferably greater than 15 kDa, more preferably greater than 17 kDa, and / or less than 150 kDa, more preferably less than 140 kDa, more preferably less than 130 kDa, more preferably less than 120 kDa, or from 1 to 100 kDa, or from 1 to 50 kDa, or from 1 to 25 kDa, or from 15 to 120 kDa, or from 20 to 120 kDa, or from 25 to 120 kDa, or from 25 to 110 kDa, or from 25 to 100 kDa.

[0020] The oligomer component should include one or more reactive oligomers. As used herein, "reactive" means the ability to undergo a chemical reaction, preferably a polymerization reaction, with another molecule. Thus, a reactive compound is said to have at least one reactive group or functional group. Such reactive groups or functional groups are preferably polymerizable groups. Although some non-reactive oligomers can be used in certain embodiments of the present invention, a higher proportion of reactive oligomers is preferred. In one embodiment, the oligomer component consists of or consists essentially of reactive oligomers.

[0021] In other embodiments, the reactive oligomer is telechelic. As used herein, "telechelic" means that such a component (i.e., the oligomer in this example) contains reactive end groups on all chain ends capable of forming intra- and intermolecular bonds.

[0022] The reactive oligomer component according to the present invention preferably comprises, consists essentially of, or consists of a reactive oligomer having at least one polymerizable group. In a preferred embodiment, the reactive oligomer component consists of a reactive oligomer having at least one polymerizable group. The polymerizable group can be of any known type. However, in one embodiment, the polymerizable group can comprise, consist essentially of, or consist of an acrylate group or a methacrylate group, or any combination thereof. The reactive oligomer is preferably an ethylenically unsaturated polymerizable compound containing one or more reactive ethylenic double bonds.

[0023] The polymerizable group can be present at any possible point along the length of the reactive oligomer and can be present as a polymerizable backbone group or a polymerizable end group. The polymerizable backbone group is present along a straight chain or branched from a straight chain along the length of the oligomer, while the polymerizable end group is a polymerizable group present at the end of the oligomer. The polymerizable group can be present, for example, at the end of the oligomer (referred to herein as a "terminal point" as a synonym), in a branched or forked pattern, etc., alone or directly or indirectly adjacent to other polymerizable groups. In a preferred embodiment, the polymerizable group comprises, consists essentially of, or consists of a polymerizable end group.

[0024] The reactive oligomers according to the present invention can be of any known type that is consistent with the definitions specified elsewhere in this specification. However, according to a first aspect, the oligomer component comprises, consists of, or consists essentially of one or more urethane oligomers, preferably reactive urethane oligomers. The urethane oligomer contains at least one urethane group or moiety, and preferably contains at least a main chain, a polymerizable group, and a urethane group linking the main chain to the polymerizable group. In various embodiments, the reactive oligomer contains from 0 to 5 urethane groups, or 4 or more urethane groups. According to a particular embodiment, the urethane oligomer comprises the reaction product of (i) a hydroxy-functional or thiol-functional main chain compound such as a polyol; (ii) an isocyanate compound, preferably a polyisocyanate; and (iii) an isocyanate-reactive hydroxyl-functional endcapper, preferably also having a (meth)acrylate moiety. In a preferred embodiment, the urethane oligomer has an Mn of from 1000 g / mol to 10,000 g / mol, or from 1200 g / mol to 9,000 g / mol.

[0025] Examples of suitable hydroxy-functional or thiol-functional main chain compounds include polyether polyols, polyester polyols, polycarbonate polyols, polycaprolactone polyols, acrylic polyols, and other polyols. These polyols may be used alone or in combination of two or more. In a preferred embodiment, the main chain of the urethane oligomer comprises the reaction product of a polyether polyol. In one embodiment, the main chain comprises the reaction product of polypropylene glycol (PPG). As used herein, compounds derived from polypropylene glycol include end-capped PPG such as EO end-capped PPG. There are no specific restrictions on the mode of polymerization of the structural units in these polyols. Each of random polymerization, block polymerization, or graft polymerization is acceptable.

[0026] As used herein, a block copolymer means a portion of an oligomer or polymer that contains many constitutional units, with at least one constitutional unit containing features that are not present in adjacent portions. As used herein, mono-, di-, and triblock copolymers refer to the average amounts of specific blocks present in the oligomer. In a preferred embodiment, a specific block refers to a polyether block derived from one or more polyols, preferably polyether polyols, described elsewhere herein. In one embodiment, the blocks referred to by mono-, di-, and / or tri-block copolymers are polyether blocks derived from one or more polyols described elsewhere herein. In one embodiment, a monoblock copolymer can be described as a copolymer having an average of about 1 unit, or only about 0.9 to less than 1.5 units, of a specific block such as a polyether block. In one embodiment, a diblock copolymer can be described as a copolymer having an average of about 2 units, or at least 1.5 to less than 2.5 units, of a specific block such as a polyether block. In one embodiment, a triblock copolymer can be described as a copolymer having an average of about 3 units, or at least 2.5 to less than 3.5 units, of a specific block such as a polyether block. The number of polyether units in a given oligomer can be determined by the number of polyether polyol molecules utilized in the synthesis of a single oligomer.

[0027] Examples of the polyether polyol include polyethylene glycol, polypropylene glycol, polypropylene glycol-ethylene glycol copolymer, polytetramethylene glycol, polyhexamethylene glycol, polyheptamethylene glycol, polydecamethylene glycol, polyether diol obtained by ring-opening copolymerization of two or more ion-polymerizable cyclic compounds, and the like. Here, examples of the ion-polymerizable cyclic compound include cyclic ethers such as ethylene oxide, isobutene oxide, tetrahydrofuran, 2-methyltetrahydrofuran, 3-methyltetrahydrofuran, dioxane, trioxane, tetraoxane, cyclohexene oxide, styrene oxide, epichlorohydrin, isoprene monooxide, vinyl oxetane, vinyltetrahydrofuran, vinylcyclohexene oxide, phenyl glycidyl ether, butyl glycidyl ether, and glycidyl benzoate. Specific examples of combinations of two or more ion-polymerizable cyclic compounds include binary copolymers such as combinations for producing tetrahydrofuran and 2-methyltetrahydrofuran, tetrahydrofuran and 3-methyltetrahydrofuran, and tetrahydrofuran and ethylene oxide; and ternary copolymers such as combinations for producing combinations such as tetrahydrofuran, 2-methyltetrahydrofuran, and ethylene oxide, and combinations for producing tetrahydrofuran, butene-1-oxide, and ethylene oxide. The ring-opening copolymers of these ion-polymerizable cyclic compounds may be random copolymers or block copolymers.

[0028] These polyether polyols include commercially available products such as PTMG1000, PTMG2000 (manufactured by Mitsubishi Chemical Corp.), PEG#1000 (manufactured by Nippon Oil and Fats Co., Ltd.), PTG650(SN), PTG1000(SN), PTG2000(SN), PTG3000, PTGL1000, and PTGL2000 (manufactured by Hodogaya Chemical Co., Ltd.), PEG400, PEG600, PEG1000, PEG1500, PEG2000, PEG4000, and PEG6000 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), P710R, P1010, P2010, and 1044 Pluracol® P series (manufactured by BASF), PPG725, PPG1000, PPG2000, PPG3000, PPG4000, and PPG8000 of the Acclaim® series and Acrol®, and the Multranol Acclaim® series (manufactured by Covestro) including PO / EO polyether diols having a molecular weight of 2800 or 4000. Further, AGC Chemicals offers diols under the trade name Preminol®, such as Preminol S 4013F (Mw 12,000), Preminol 4318F (Mw 18,000), and Preminol 5001F (Mw 4,000).

[0029] Examples of the polyester polyol include polyester diols obtained by reacting a polyhydric alcohol with a polybasic acid. Examples of the polyhydric alcohol include ethylene glycol, polyethylene glycol, tetramethylene glycol, polytetramethylene glycol, 1,6 - hexanediol, 3 - methyl - 1,5 - pentanediol, 1,9 - nonanediol, 2 - methyl - 1,8 - octanediol, and the like. Examples of the polybasic acid include phthalic acid, dimer acid, isophthalic acid, terephthalic acid, maleic acid, fumaric acid, adipic acid, sebacic acid, and the like.

[0030] These polyester polyol compounds are commercially available under trade names such as MPD / IPA500, MPD / IPA1000, MPD / IPA2000, MPD / TPA500, MPD / TPA1000, MPD / TPA2000, Kurapol (registered trademark) A-1010, A-2010, PNA-2000, PNOA-1010, and PNOA-2010 (manufactured by Kuraray Co., Ltd.).

[0031] Triols such as polyester triols or polyether triols are also known. Particularly preferred for use herein is an oligo-triol having the general formula: A(----OH)3; wherein A is a chemical organic structure such as an aliphatic, alicyclic, aromatic, or heterocyclic structure, and "----" is, by way of example only, an oligomer chain such as a polyether chain, a polyester chain, a polyhydrocarbon chain, or a polysiloxane chain, and "OH" is a terminal hydroxy group. In one embodiment, the triol comprises, consists of, or consists essentially of a polyether triol, a PO homopolymer, a PE homopolymer, a PO-EO block copolymer, a random copolymer, or a hybrid block-random copolymer. In practice, the polyether triol can be based on glycerol or trimethylolpropane, PO, EO, or having EO on the terminal block or internal block, and a PO and EO copolymer having an MW of 500 to 15,000 daltons. Another type of polyether triol is a copolymer based on glycerol or trimethylolpropane, such as THF-PO, THF-EO, THF-PO-EO, or THF-EO-PO, having a molecular weight of about 500 to 15,000 g / mol. In one embodiment, the triol is derived from certain bio-based or natural reactants such as vegetable oils and fats.

[0032] Commercial examples of suitable triols include related propylene oxide-based polyether triols available from Carpenter under the Carpol® GP designation such as GP-1000, GP-1500, GP-1500-60, GP-3000, GP-4000, GP-5017, GP-5017-60, GP-5171, GP-6015, GP-6015-60, GP-6037-60, and GP-700. Further triols are available commercially under the Arcol® brand from Covestro, Arcol LHT-240 (manufacturer-reported molecular weight “Mw” is approximately 700 g / mol), Arcol LHT-112 (Mw 1500 g / mol), Arcol LHT LG-56 (Mw 3000 g / mol), and Arcol LHT-42 (Mw 4200 g / mol), under the Multranol® trade name, for example Multranol 9199 (Mw 4525 g / mol), Multranol 3900 (Mw 4800 g / mol), Multranol 3901 (Mw 6000 g / mol), and Multranol 9139 (Mw 6000 g / mol), and under the trade name Acclaim® such as Acclaim 703 (Mw 700 g / mol), Acclaim 3300N (Mw 3000 g / mol), Acclaim 6300 (Mw 6000 g / mol), and Acclaim 6320 (Mw 6000 g / mol). Additionally, AGC Chemicals offers triols under the Preminol® trade name such as Preminol S 3011 (Mw 10,000 g / mol), Preminol 7001K (Mw 7,000 g / mol), and Preminol 7012 (Mw 10,000 g / mol).

[0033] There is no specific limitation on the number of R-H groups present in the hydroxyl or thiol functional main-chain compounds (OH and SH respectively), but preferably, the hydroxyl or thiol functional main-chain compounds have 4 or fewer R-H groups. In a preferred embodiment, (i) includes a hydroxyl functional main-chain compound having at least 2 hydroxyl groups, or at least 3 hydroxyl groups, or 4 hydroxyl groups.

[0034] The theoretical molecular weights derived from the hydroxyl values of these polyols are usually from about 50 g / mol to about 15,000 g / mol, preferably from about 500 to 12,000 g / mol, or from about 1,000 to about 8,000 g / mol.

[0035] In addition to hydroxyl functional compounds such as polyols, thiol functional compounds can also be used as (i). Suitable thiol functional compounds can be prepared from suitable hydroxyl functional compounds by well-known methods.

[0036] In a preferred embodiment, (i) comprises, consists of, or consists essentially of a hydroxyl functional main-chain compound. In one embodiment, the hydroxyl functional main-chain compound includes a polyether, polyester, polybutadiene, polycarbonate, or silicone moiety.

[0037] The reactive urethane oligomer also preferably comprises a reaction product of a (poly) isocyanate compound. A reaction product of a (poly) isocyanate compound, preferably a diisocyanate compound, can be used to form urethane groups or moieties in the reactive urethane oligomer according to the first aspect of the present invention. As used herein, an isocyanate compound is defined as any organic compound having at least one isocyanate group per molecule. Examples of suitable isocyanates include diisocyanates such as 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, (hydrogenated) xylylene diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, 1,5-naphthalene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, 3,3'-dimethyl-4,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 3,3'-dimethylphenylene diisocyanate, 4,4'-biphenylene diisocyanate, 1,6-hexane diisocyanate, isophorone diisocyanate, methylene bis(4-cyclohexyl isocyanate), 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, hexamethylene diisocyanate, 2,4- and / or 4,4'-methylenedicyclohexyl diisocyanate, methylenediphenyl diisocyanate, tetramethylxylylene diisocyanate, 1,5-pentane diisocyanate, bis(2-isocyanato-ethyl) fumarate, 6-isopropyl-1,3-phenyl diisocyanate, 4-diphenylpropane diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate, tetramethylxylylene diisocyanate, and lysine isocyanate, among others.

[0038] These diisocyanate compounds may be used alone or in combination of two or more. Preferred diisocyanates are isophorone diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, hexamethylene diisocyanate, 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate.

[0039] As used herein, "polyisocyanate" indicates that the isocyanate compound has two or more isocyanate moieties per molecule. In one embodiment, the oligomer component comprises, consists essentially of, or consists of a urethane oligomer that is a reaction product of one or more polyisocyanates. In addition to the above diisocyanates, polyisocyanates having three isocyanate groups per molecule, i.e., triisocyanates, can also be used. Known triisocyanates include biurets produced from hexamethylene diisocyanate (HDI) or HDI trimers, which are commercially available from Covestro under the trade name Desmodur®, including but not limited to Desmodur N 3200, Desmodur N 3300, Desmodur N 3390, Desmodur N 3600, Desmodur N 3800, Desmodur N 3900, Desmodur N XP 2580, Desmodur XP 2599, Desmodur XP 2675, Desmodur XP 2731, Desmodur XP 2714 and Desmodur XP 2803.

[0040] Further commercially available triisocyanates include Vestanat® T (IPDI-trimer) and HT (HDI-trimer) series of polyisocyanate crosslinking agents for 2K systems available from Evonik.

[0041] The reactive urethane oligomer also preferably comprises (iii) the reaction product of a hydroxyl-functional end capper. The compound described in (iii) is preferably reactive with the isocyanate compound from (ii). Preferably, the urethane oligomer also comprises, as (iii), the reaction product of an isocyanate-reactive compound having an ethylenically unsaturated moiety. Preferably, the ethylenically unsaturated moiety is a (meth)acrylate moiety. Any suitable (meth)acrylate including monomers and oligomers can be used, but (meth)acrylate monomers are preferred. Such isocyanate-reactive (meth)acrylates preferably include hydroxyl group-containing (meth)acrylate compounds, and such compounds are known to be reactive with isocyanates including the polyisocyanates of (ii). Examples of hydroxyl group-containing (meth)acrylates include (meth)acrylates derived from (meth)acrylic acid and epoxy, and (meth)acrylates containing alkylene oxide, more specifically, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, and hydroxyethyl caprolactone acrylate, ethoxylated trimethylolpropane diacrylate, glycerol di(meth)acrylate, and glycerol acrylate methacrylate (i.e., 3-(acryloyloxy)-2-hydroxypropyl methacrylate). In a preferred embodiment, (iii) comprises, consists essentially of, or consists of hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, caprolactone (meth)acrylate, glycerol acrylate methacrylate, glycerol di(meth)acrylate, or combinations thereof.

[0042] The hydroxyl-functional end-capper (iii) preferably further contains one or two ethylenically unsaturated moieties, and more preferably, the hydroxyl-functional end-capper (iii) further contains one ethylenically unsaturated moiety. The compound described in (iii) may have two or more hydroxyl groups per molecule.

[0043] In the reaction of the components used to produce the urethane oligomer, one or more urethanization catalysts are also preferably used. Examples of such catalysts include copper naphthenate, cobalt naphthenate, zinc naphthenate, bismuth, di-n-butyltin dilaurate, triethylenetriamine, and triethylenediamine-2-methyltriethylenetriamine. The catalyst can be used in any suitable amount, or for example, in an amount of about 0.01 to about 1% by weight of the total amount of the reactants. The reaction can be carried out at any suitable temperature, such as a temperature of about 10 to about 90 °C, preferably about 30 to about 80 °C.

[0044] In one embodiment, the composition or formulation further comprises at least one oligomer comprising the reaction product of a single PPG diol as (i), a single diisocyanate compound as (ii), and a hydroxyl-functional (meth)acrylate compound as (iii).

[0045] The oligomers (a), reactants (i), (ii), and (iii) are selected and configured in a predetermined ratio. The composition includes at least one oligomer (a) in which the molar ratio of the number of isocyanate groups in (ii) to the number of hydroxyl and thiol groups in (i) is 1.0 or less. One or more oligomers (a) are reaction products of (iii) a hydroxyl-functional end capper further including an ethylenically unsaturated moiety, (ii) an isocyanate compound, and (i) a hydroxy-functional or thiol-functional backbone compound, and the molar amount of the isocyanate groups in (ii) is equal to or less than the molar amount of the hydroxyl and thiol groups in (i). Thus, since the oligomer described in (a) is the reaction product of all three components (iii), (ii), and (i), one or more oligomers (a) are hydroxy-functional or thiol-functional. In one embodiment, the composition includes at least one oligomer (a) in which the molar ratio of the number of isocyanate groups in (ii) to the number of hydroxyl and thiol groups in (i) is 2:3 or more and 1.0 or less. Thus, in certain embodiments, the composition preferably has at least one oligomer (a) having the aforementioned molar ratio of about 0.67 to 1.0, or equal to 1. Surprisingly, the inventors have discovered that oligomers configured in this way (otherwise conforming to the requirements and preferences specified herein) tend to have lower viscosity values. Using such oligomers tends to minimize the need for large amounts of volatile diluents, which is useful since they are included in large amounts in the overall composition.

[0046] Thus, in one embodiment, the composition or formulation includes at least one oligomer having a viscosity of less than 15 Pa·s, or less than 12, or less than 10 Pa·s, or from 1 to 15 Pa·s, or from 2 to 12 Pa·s, or from 3 to 10 Pa·s, where the viscosity is measured at 25° C. and a shear rate of 2500 s -1 -1.

[0047] The various oligomers of the first aspect can be configured to have a wide range of functionality. In one embodiment, at least one monofunctional oligomer is utilized. As used herein, "monofunctional" means having from 0.5 to 1.4 polymerizable groups per molecule, as determined, for example, by nuclear magnetic resonance spectroscopy (NMR).

[0048] In one embodiment, bifunctional oligomers and / or trifunctional oligomers can be additionally or alternatively used. As used herein, "bifunctional" means having from 1.95 to 2.05 polymerizable groups per molecule, as determined, for example, by NMR. Similarly, "trifunctional" as used herein means having an average of from 2.95 to 3.05 polymerizable groups per molecule. In a preferred embodiment, the oligomer component comprises, consists essentially of, or consists of one or more reactive urethane oligomers having an average (meth)acrylate functionality of 1.5 to 4.2, or 1.8 to 3.8, or 1.8 to 3.2, or 1.8 to 2.8. In one embodiment, the average (meth)acrylate functionality of the oligomer component is 1.5 to 4.2, or 1.8 to 3.8, or 1.8 to 3.2, or 1.8 to 2.8.

[0049] In a preferred embodiment, the composition or formulation contains at least one oligomer that is bifunctional or higher to facilitate suitable crosslinking for use as a primary coating for an optical fiber. In a further embodiment, the composition or formulation contains a mixture of different oligomers having different functionalities, such as at least one monofunctional oligomer and at least one bifunctional oligomer, or at least one monofunctional oligomer and at least one trifunctional oligomer, or at least one monofunctional oligomer, at least one bifunctional oligomer, and at least one trifunctional oligomer. Of course, other combinations to which the present invention is applicable can also be envisioned by those skilled in the art.

[0050] According to many embodiments of the first aspect, the composition or formulation contains more than one oligomer. In an embodiment of the first aspect, the optical fiber primary coating composition comprises one or more oligomers that are reaction products of (a) (i) a hydroxy-functional or thiol-functional backbone compound, (ii) an isocyanate compound, and (iii) a hydroxy-functional endcapper further comprising an ethylenically unsaturated moiety, whereby the molar ratio of (ii) to (i) is 1.0 or less as described above, and optionally, (b) one or more urethane (meth)acrylate oligomers other than those mentioned in (a). In an embodiment of the first aspect, one or more oligomers as described in (a) are present in a large amount relative to the entire relevant composition, such as 20 wt% or more, or 30 wt% or more, 40 wt% or more, and 95 wt% or less, or 90 wt% or less, or 80 wt% or less, or 70 wt% or less. When the optical fiber primary coating composition does not contain oligomer (b) and one or more oligomers (a) present in the optical fiber primary coating composition are monofunctional with respect to the polymerizable groups, one of ordinary skill in the art will understand that one or more reactive diluent monomers (c) need to be present and that at least a portion of (c) needs to be at least bifunctional with respect to the polymerizable groups in order for the optical fiber primary coating composition to form a network. When the optical fiber primary coating composition does not contain oligomer (b) and does not contain reactive diluent monomer (c), or one or more reactive diluent monomers (c) are monofunctional with respect to the polymerizable groups, one of ordinary skill in the art will understand that at least a portion of one or more oligomers (a) needs to be at least bifunctional in order for the optical fiber primary coating composition to form a network.

[0051] One or more oligomers (a) are incorporated in such large amounts throughout the composition that they are preferably configured to have a viscosity low enough to allow for sufficient processing in optical fiber coating applications. As described above, the aforementioned molar ratio of (ii) to (i) can beneficially contribute to this property of the oligomer (a). Alternatively or additionally, the total number of urethane bonds present in one or more oligomers (a) can also beneficially contribute thereto. Thus, in one embodiment, the oligomer described in (a) has 1.8 to 2.2 urethane bonds per molecule. Thirdly, the inventors have surprisingly discovered that oligomers with a sufficiently low viscosity can be obtained by configuring the oligomer to be terminated with a hydroxyl or thiol group at one end.

[0052] In other embodiments of the first aspect, the oligomer (b) is preferably present in an amount of 29.95 wt% or less based on the entire relevant composition. The oligomer (b) may also comprise a reaction product of (i) a hydroxy-functional main chain compound, (ii) an isocyanate compound, and (iii) a hydroxyl-functional endcapper. However, in contrast to the oligomer (a), according to certain embodiments, in the urethane (meth)acrylate oligomer (b), the molar ratio of the number of isocyanate groups in (ii) to the number of hydroxyl groups in (i) is greater than 1.0, or about 1.5 to about 2.0.

[0053] According to an embodiment of the first aspect, the concentration of acrylate groups in the optical fiber primary coating composition and / or the concentration of urethane groups in the optical fiber primary coating composition and / or the concentration of acrylate groups in the oligomers present in the optical fiber primary coating composition can beneficially contribute to the ability to reduce the volatile content of the optical fiber primary coating composition, yet still be suitable for use in optical fiber coating applications, particularly maintaining an acceptable viscosity, curing rate, and performance on the fiber, in particular, a curing rate (measured by low T30%, a maximum modulus of elasticity, particularly less than 1.2 seconds, more preferably less than 1.0 second), a low modulus of elasticity (measured by a low G' value, particularly less than 600 kPa, more preferably less than 500 kPa, more preferably less than 400 kPa, more preferably less than 300 kPa), and / or a low viscosity (particularly less than 9 Pascal seconds, more preferably less than 5 Pascal seconds). The concentration of acrylate groups is preferably 2.50 mol / kg or less, more preferably 2.00 mol / kg or less, more preferably 1.50 mol / kg or less, more preferably 1.20 mol / kg or less, more preferably 1.00 mol / kg or less, more preferably 0.80 mol / kg or less, based on the entire relevant composition. The concentration of urethane groups is preferably 0.20 mol / kg or more, or 0.25 mol / kg or more, or 0.30 mol / kg or more, or 0.31 mol / kg or more, or 0.35 mol / kg or more, or 0.40 mol / kg or more, or 0.45 mol / kg or more, or 0.50 mol / kg or more, preferably less than 1.5 mol / kg, or 0.90 mol / kg or less, preferably 0.70 mol / kg or less, based on all relevant compositions. As used herein, the concentration of acrylate groups and the concentration of urethane groups are determined by calculation from the charge ratio of the components.The total concentration of acrylate groups present in oligomers (a) and (b) is preferably 0.05 mol / kg oligomer (a)+(b) or less, or 0.80 mol / kg oligomer (a)+(b) or less, or 0.70 mol / kg oligomer (a)+(b) or less, or 0.60 mol / kg oligomer (a)+(b) or less, or 0.50 mol / kg oligomer (a)+(b) or less, or 0.40 mol / kg oligomer (a)+(b) or less, or 0.30 mol / kg oligomer (a)+(b) or less, or 0.28 mol / kg oligomer (a)+(b) or less.

[0054] Regardless of whether included in the first aspect, the total oligomer content (whether (a) alone or, if present, including (b) as well) is preferably very high relative to the weight of the overall composition to which such oligomer or oligomers pertain. In one embodiment, the oligomer is present in an amount of at least 70 wt%, or at least 80 wt%, or at least 90 wt%, or at least 95 wt%, or at least 98 wt% relative to the weight of the overall composition. Preferably, the oligomers by (a) and (b) are present in an amount of 80 wt% or more and 96 wt% or less relative to the weight of the overall composition. Reactive diluent component (c)

[0055] The composition according to the first aspect of the present invention also includes a diluent component (c); that is, an aggregate of one or more individual diluents having one or more specific structures or types. As used herein, "diluent" means a substance that reduces the viscosity of the larger composition to which it is added or with which it is associated. Various diluents are used to maximize the fluidity, and thus processability, of the optical fiber coating compositions with which they are associated.

[0056] To maximize the curability of the related composition, the diluent component preferably comprises, consists of, or consists essentially of a reactive diluent. As specified with respect to the suitability of the oligomeric components described elsewhere herein, "reactive" means the ability to undergo a chemical reaction, preferably a polymerization reaction, with another molecule. Thus, a reactive compound is said to have at least one reactive or functional group. Such reactive or functional groups are preferably polymerizable groups.

[0057] More preferably, the diluent component comprises, consists of, or consists essentially of a reactive diluent monomer. A monomer is a molecule of low relative molecular weight, the structure of which is capable of undergoing polymerization and thereby contributing a structural unit to the essential structure of a polymer. As used herein, a component is considered a monomer if it further has a number average molecular weight (Mn) of less than about 1000 g / mol. In one embodiment, the reactive diluent component consists of one or more reactive diluent monomers having an Mn of about 86 g / mol (molar mass of methyl acrylate) to 750 g / mol, or 100 g / mol to 350 g / mol, as measured by NMR method. In an embodiment, the reactive diluent has an Mn of less than 500 g / mol.

[0058] The diluent component according to the present invention comprises, consists essentially of, or consists of a reactive diluent monomer having at least one polymerizable group. In a preferred embodiment, the reactive diluent monomer component consists of reactive diluent monomers having an average of one polymerizable group. The polymerizable groups of the reactive diluent monomers are preferably capable of (co)polymerizing with the polymerizable groups present in the related reactive oligomeric components.

[0059] The polymerizable group of the reactive diluent may be of any known type. However, in one embodiment, the polymerizable group can include, consist essentially of, or consist of acrylate groups, acrylamide groups, or N-vinylamide groups, or any combination thereof. The reactive diluent is preferably an ethylenically unsaturated polymerizable compound containing at least one reactive olefin double bond.

[0060] The polymerizable group may be present at any possible position along the length of the reactive diluent. However, in a preferred embodiment, the polymerizable group includes, consists essentially of, or consists of polymerizable end groups.

[0061] The diluent component according to the present invention can include any known type of compound or substance that is consistent with the definitions specified elsewhere in this specification. However, in a preferred embodiment, the diluent component includes, consists essentially of, or consists of one or more reactive diluent monomers containing one double bond.

[0062] Typical examples of such reactive diluent monomers containing one double bond are alkyl or hydroxyalkyl acrylates, such as methyl, ethyl, butyl, 2-phenoxyethyl, 2-ethylhexyl, and 2-hydroxyethyl acrylate, isobornyl acrylate, methyl and ethyl acrylate, lauryl acrylate, ethoxylated nonyl-phenol acrylate, and diethylene-glycol-ethyl-hexyl acrylate (DEGEHA). Further examples of these monomers are acrylonitrile, acrylamide, N-substituted acrylamide, vinyl esters such as vinyl acetate, styrene, alkylstyrene, halostyrene, N-vinylpyrrolidone, N-vinylamide such as N-vinylcaprolactam, vinyl chloride and vinylidene chloride. Examples of monomers containing two or more double bonds are ethylene glycol diacrylate, propylene glycol diacrylate, tripropylene glycol diacrylate, neopentyl glycol diacrylate, hexamethylene glycol diacrylate, bisphenol A diacrylate, 4,4'-bis(2-acryloyloxyethoxy)diphenylpropane, trimethylolpropane triacrylate, pentaerythritol triacrylate and tetraacrylate, and vinyl acrylate.

[0063] In a preferred embodiment, when used, component (c) comprises 2-ethylhexyl acrylate, 2-phenoxyethyl acrylate, 2-(2-ethoxyethoxy)ethyl acrylate, n-vinylpyrrolidone, dimethylacrylamide, n-vinylcaprolactam, ethoxylated 2-phenoxyethyl acrylate, 4-hydroxybutyl acrylate, lauryl acrylate, isobornyl acrylate, caprolactone acrylate, ethoxylated nonylphenol acrylate, tridecyl acrylate, or isodecyl acrylate, or combinations thereof.

[0064] In a preferred embodiment, the diluent component comprises, consists essentially of, or consists of one or more monofunctional diluent monomers. In a preferred embodiment, the diluent component comprises, consists of, or consists essentially of functional monomers such as (meth)acrylic monomers.

[0065] One or more of the aforementioned diluents can be used in the composition according to the present invention in any suitable amount to adjust the viscosity of the relevant formulation suitable for the optical fiber coating process used, in accordance with methods well known in the technical field to which the present invention is applied, and can be selected alone or in combination with one or more of the types listed herein.

[0066] However, in various preferred embodiments, it is desirable to minimize the amount of low molecular weight components present in the composition or formulation. This is because such components are inherently more volatile than their higher molecular weight oligomeric analogs and have a greater tendency to evaporate or separate from the liquid composition during coating. Such problems are particularly acute in situations where the composition is exposed to and maintained at higher temperatures, such as those experienced during high-speed coating and processing onto an optical fiber. Evaporation of volatile substances during the optical fiber curing process is highly undesirable because such volatile components will later condense or agglomerate on the inner surface of the tube in which the fiber coating process is carried out. As more components adhere to the tube surface, they inevitably impede the ability of the radiation source to efficiently cure the optical fiber coating composition because they prevent some of the light from reaching the tube surface. In addition to this, such volatile substances harden the inner surface of the tube, thus requiring more frequent and inconvenient process stop and cleaning operations. The inventors have surprisingly found that by constructing a composition or formulation of the type defined herein, such as by including the aforementioned oligomers (a) and (b), it is possible to reduce the amount of reactive diluent present in the composition, while still being able to maintain a sufficient curing rate, processability, and performance on the fiber.

[0067] Thus, in a preferred embodiment, component (c) is present in an amount of less than 30% by weight, or less than 29.95% by weight, or less than 20% by weight, or less than 10% by weight, or less than 5% by weight, or less than 2% by weight, based on the total weight of the composition or formulation with which it is associated. In yet another preferred embodiment, component (c) is not present at all in the composition or formulation. Photoinitiator component (d)

[0068] According to a first aspect, the composition and / or formulation preferably comprises a photoinitiator component; that is, an aggregate of one or more individual photoinitiators having one or more specific structures or types. A photoinitiator is a compound that undergoes a chemical change by the action of light or by a synergistic action between the action of light and the electronic excitation of a sensitizing dye to produce at least one of a radical, an acid, and a base. Well-known types of photoinitiators include cationic photoinitiators and free radical photoinitiators. According to one embodiment of the present invention, the photoinitiator is a free radical photoinitiator.

[0069] In one embodiment, the photoinitiator component comprises, consists of, or consists essentially of one or more acylphosphine oxide photoinitiators. Acylphosphine oxide photoinitiators are known and are disclosed, for example, in U.S. Pat. Nos. 4,324,744, 4,737,593, 5,942,290, 5,534,559, 6,020,529, 6,486,228, and 6,486,226. Preferred types of acylphosphine oxide photoinitiators for use in the photoinitiator component include bisacylphosphine oxide (BAPO) or monoacylphosphine oxide (MAPO). More specifically, 2,4,6-trimethylbenzoyl ethoxyphenylphosphine oxide (CAS No. 84434-11-7) or 2,4,6-trimethylbenzoyl diphenylphosphine oxide (CAS No. 127090-72-6) may be mentioned.

[0070] The photoinitiator component can also optionally contain, consist of, or consist essentially of an α-hydroxyketone photoinitiator. For example, suitable α-hydroxyketone photoinitiators are α-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropanone, 2-hydroxy-2-methyl-1-(4-isopropylphenyl)propanone, 2-hydroxy-2-methyl-1-(4-dodecylphenyl)propanone, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]-phenyl}-2-methyl-propan-1-one and 2-hydroxy-2-methyl-1-[(2-hydroxyethoxy)phenyl]propanone.

[0071] In another embodiment, the photoinitiator component includes, consists of, or consists essentially of α - aminoketones such as 2 - methyl - 1 - [4 - (methylthio)phenyl] - 2 - (4 - morpholinyl) - 1 - propanone, 2 - benzyl - 2 - (dimethylamino) - 1 - [4 - (4 - morpholinyl)phenyl] - 1 - butanone, 2 - (4 - methylbenzyl)-2 - (dimethylamino) - 1 - [4 - (4 - morpholinyl)phenyl] - 1 - butanone or 2 - benzyl - 2 - (dimethylamino) - 1 - [3,4 - dimethoxyphenyl] - 1 - butanone; benzophenones such as benzophenone, 2,4,6 - trimethylbenzophenone, 4 - methylbenzophenone, 2 - methylbenzophenone, 2 - methoxycarbonylbenzophenone, 4,4’ - bis(chloromethyl) - benzophenone, 4 - chlorobenzophenone, 4 - phenylbenzophenone, 4,4’ - bis(dimethylamino) - benzophenone, 4,4’ - bis(diethylamino)benzophenone, methyl 2 - benzoylbenzoate, 3,3’ - dimethyl - 4 - methoxybenzophenone, 4 - (4 - methylphenylthio)benzophenone, 2,4,6 - trimethyl - 4’ - phenyl - benzophenone or 3 - methyl - 4’ - phenyl - benzophenone; ketal compounds such as 2,2 - dimethoxy - 1,2 - diphenyl - ethanone; and monomeric or dimeric phenylglyoxylic acid esters such as methyl phenylglyoxylate, such as 5,5’ - oxo - bis(ethylenedioxydicarbonylphenyl) or 1,2 - (benzoylcarboxy)ethane.

[0072] More preferably suitable photoinitiators for use in the photoinitiator component include oxime esters such as those disclosed in U.S. Patent No. 6,596,445. Another class of photoinitiators suitable for use in the photoinitiator component includes, for example, phenylglyoxalates such as those disclosed in U.S. Patent No. 6,048,660.

[0073] In another embodiment, the photoinitiator component can comprise, consist of, or consist essentially of one or more alkyl-, aryl-, or acyl-substituted compounds not described hereinabove.

[0074] According to another embodiment, the composition can contain a photoinitiator that is an alkyl-, aryl-, or acyl-substituted compound. In one embodiment, the alkyl-, aryl-, or acyl-substituted photoinitiator has or is centered about an atom in a carbon (Group 14) group. In such a case, upon excitation (through absorption of radiation), the Group 14 atom present in the photoinitiator compound forms a radical. Thus, such a compound can generate a radical having or centered about an atom selected from the group consisting of silicon, germanium, tin, and lead. In one embodiment, the alkyl-, aryl-, or acyl-substituted photoinitiator is an acylgermanium compound. Such photoinitiators are described in US9708442, assigned to Covestro (Netherlands) B.V., which is hereby incorporated by reference in its entirety. Specific known acylgermanium photoinitiators include benzoyltrimethylgermanium (BTG), tetraacylgermanium, or bisacylgermanoyl (commercially available as Ivocerin® from Ivoclar Vivadent AG, 9494 Schaan / Liechtenstein).

[0075] The photoinitiators according to the present invention can be used alone or in one or more combinations as a blend. Suitable photoinitiator blends are disclosed, for example, in U.S. Patent No. 6,020,528 and U.S. Patent Application No. 60 / 498,848. According to one embodiment, the photoinitiator component comprises, for example, a photoinitiator blend of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (CAS number 162881-26-7) and 2,4,6,-trimethylbenzoylethoxyphenylphosphine oxide (CAS number 84434-11-7) in a weight ratio of about 1:11, 1:10, 1:9, 1:8 or 1:7.

[0076] Another particularly suitable photoinitiator blend is a mixture of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 2,4,6,-trimethylbenzoylethoxyphenylphosphine oxide and 2-hydroxy-2-methyl-1-phenyl-1-propanone (CAS number 7473-98-5) in a weight ratio of, for example, about 3:1:15 or 3:1:16 or 4:1:15 or 4:1:16. Another suitable photoinitiator blend is a mixture of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide and 2-hydroxy-2-methyl-1-phenyl-1-propanone in a weight ratio of, for example, about 1:3, 1:4 or 1:5.

[0077] One or more of the foregoing photoinitiators can be used in any suitable amount for use in the photoinitiator component in the composition according to the first aspect of the present invention, and can be selected alone or in one or more combinations of the types listed herein. In a preferred embodiment, the photoinitiator component comprises, consists of, or consists essentially of a free radical photoinitiator. In one embodiment, the photoinitiator component is present in an amount of about 0.1 wt% to about 10 wt%, or about 0.1 wt% to about 5 wt%, or about 1 wt% to about 5 wt%, or about 0.04 wt% to about 8 wt% based on the total weight of the composition. Additive (e)

[0078] The composition and / or formulation according to the first aspect of the present invention optionally includes an additive component; that is, an aggregate of one or more individual additives having one or more specific structures or types. Additives are also typically added to the optical fiber coating to achieve certain desirable properties such as improved adhesion to glass optical fibers, improved shelf life, improved coating oxidation and hydrolysis stability. There are many different types of desirable additives, and the present invention discussed herein is not intended to be limited thereby, and nevertheless, since they have desirable effects, they are included in the envisioned embodiments.

[0079] Examples of additives for use in the additive component include heat inhibitors intended to prevent premature polymerization, such as hydroquinone, hydroquinone derivatives, p-methoxyphenol, β-naphthol, or sterically hindered phenols such as 2,6-di(tert-butyl)-p-cresol. The shelf life in the dark can be increased, for example, by using copper compounds such as copper naphthenate, copper stearate or copper octanoate, phosphorus compounds such as triphenylphosphine, tributylphosphine, triethyl phosphite, triphenyl phosphite or tribenzyl phosphite, quaternary ammonium compounds such as tetramethylammonium chloride or trimethylbenzylammonium chloride.

[0080] To prevent atmospheric oxygen during polymerization, additives such as paraffin or similar wax-like substances can be added; these migrate to the surface at the start of polymerization due to their low solubility in the polymer and form a transparent surface layer that prevents the entry of air. Similarly, it is also possible to apply an oxygen barrier layer.

[0081] Further potentially suitable additives include light stabilizers. Examples of light stabilizers include UV absorbers, such as well-known commercially available UV absorbers of the hydroxyphenylbenzotriazole, hydroxyphenylbenzophenone, oxalamide or hydroxyphenyl-s-triazine type. It is possible to use individual such compounds or mixtures thereof, with or without using sterically hindered relatively non-basic amine light stabilizers (HALS). Sterically hindered amines are based, for example, on 2,2,6,6-tetramethylpiperidine. Examples of UV absorbers and sterically hindered amines include the following:

[0082] 2-(2-Hydroxyphenyl)-2H-benzotriazoles, such as known commercially available hydroxyphenyl-2H-benzotriazoles and benzotriazoles, which are disclosed in U.S. Patent Nos. 3,004,896; 3,055,896; 3,072,585; 3,074,910; 3,189,615; 3,218,332; 3,230,194; 4,127,586; 4,226,763; 4,275,004; 4,278,589; 4,315,848; 4,347,180; 4,383,863; 4,675,352; 4,681,905; 4,853,471; 5,268,450; 5,278,314; 5,280,124; 5,319,091; 5,410,071; 5,436,349; 5,516,914; 5,554,760; 5,563,242; 5,574,166; 5,607,987; 5,977,219; and 6,166,218, for example, 2-(2-hydroxy-5-methylphenyl)-2H-benzotriazole, 2-(3,5-di-t-butyl-2-hydroxyphenyl)-2H-benzotriazole, 2-(2-hydroxy-5-t-butylphenyl)-2H-benzotriazole, 2-(2-hydroxy-5-t-octylphenyl)-2H-benzotriazole, 5-chloro-2-(3,5-di-t-butyl-2-hydroxyphenyl)-2H-benzotriazole, 5-chloro-2-(3-t-butyl-2-hydroxy-5-methylphenyl)-2H-benzotriazole, 2-(3-sec-butyl-5-t-butyl-2-hydroxyphenyl)-2H-benzotriazole, 2-(2-hydroxy-4-octyloxyphenyl)-2H-benzotriazole, 2-(3,5-di-t-amyl-2-hydroxyphenyl)-2H-benzotriazole, 2-(3,5-bis-α-cumyl-2-hydroxyphenyl)-2H-benzotriazole, 2-(3-t-butyl-2-hydroxy-5-(2-(ω-hydroxy-octa-(ethyleneoxy)carbonyl-ethyl)-,(phenyl)-2H-benzotriazole, 2-(3-dodecyl-2-hydroxy-5-methylphenyl)-2H-benzotriazole, 2-(3-t-butyl-2-hydroxy-5-(2-octyloxycarbonyl)ethylphenyl)-2H-benzotriazole, dodecylated 2-(2-hydroxy-5-methylphenyl)-2H-benzotriazole, 2-(3-t-butyl-2-hydroxy-5-(2-octyloxycarbonylethyl)phenyl)-5-chloro-2H-benzotriazole, 2-(3-tert-butyl-5-(2-(2-ethylhexyloxy)-carbonylethyl)-2-hydroxyphenyl)-5-chloro-2H-benzotriazole, 2-(3-t-butyl-2-hydroxy-5-(2-methoxycarbonylethyl)phenyl)-5-chloro-2H-benzotriazole, 2-(3-t-butyl-2-hydroxy-5-(2-methoxycarbonylethyl)phenyl)-2H-benzotriazole, 2-(3-t-butyl-5-(2-(2-ethylhexyloxy)carbonylethyl)-2-hydroxyphenyl)-2H-benzotriazole, 2-(3-t-butyl-2-hydroxy-5-(2-isooctyloxycarbonylethyl)phenyl-2H-benzotriazole, 2,2’-methylene-bis(4-t-octyl-(6-2H-benzotriazol-2-yl)phenol), 2-(2-hydroxy-3-α-cumyl-5-t-octylphenyl)-2H-benzotriazole, 2-(2-hydroxy-3-t-octyl-5-α-cumylphenyl)-2H-benzotriazole, 5-fluoro-2-(2-hydroxy-3,5-di-α-cumylphenyl)-2H-benzotriazole, 5-chloro-2-(2-hydroxy-3,5-di-α-cumylphenyl)-2H-benzotriazole, 5-chloro-2-(2-hydroxy-3-α-cumyl-5-t-octylphenyl)-2H-benzotriazole, 2-(3-t-butyl-2-hydroxy-5-(2-isooctyloxycarbonylethyl)phenyl)-5-chloro-2H-benzotriazole, 5-trifluoromethyl-2-(2-hydroxy-3-α-cumyl-5-t-octylphenyl)-2H-benzotriazole, 5-trifluoromethyl-2-(2-hydroxy-5-t-octylphenyl)-2H-benzotriazole, 5-trifluoromethyl-2-(2-hydroxy-3,5-di-t-octylphenyl)-2H-benzotriazole, methyl 3-(5-trifluoromethyl-2H-benzotriazol-2-yl)-5-t-butyl-4-hydroxyhydrocinnamate, 5-butylsulfonyl-2-(2-hydroxy-3-α-cumyl-5-t-octylphenyl)-2H-benzotriazole, 5-trifluoromethyl-2-(2-hydroxy-3-α-cumyl-5-t-butylphenyl)-2H-benzotriazole, 5-trifluoromethyl-2-(2-hydroxy-3,5-di-t-butylphenyl)-2H-benzotriazole, 5-trifluoromethyl-2-(2-hydroxy-3,5-di-α-cumylphenyl)-2H-benzotriazole, 5-butylsulfonyl-2-(2-hydroxy-3,5-di-t-butylphenyl)-2H-benzotriazole and 5-phenylsulfonyl-2-(2-hydroxy-3,5-di-t-butylphenyl)-2H-benzotriazole.,

[0083] As another example, 2-hydroxybenzophenone, for example, 4-hydroxy, 4-methoxy, 4-octyloxy, 4-decyloxy, 4-dodecyloxy, 4-benzyloxy, 4,2’,4’-trihydroxy and 2’-hydroxy-4,4’-dimethoxy derivatives can be mentioned.

[0084] Still another exemplary class includes esters of substituted and unsubstituted benzoic acids, such as 4-tert-butylphenyl salicylate, phenyl salicylate, octylphenyl salicylate, dibenzoyl resorcinol, bis(4-tert-butylbenzoyl) resorcinol, benzoyl resorcinol, 2,4-di-tert-butylphenyl 3,5-di-tert-butyl-4-hydroxybenzoate, hexadecyl 3,5-di-tert-butyl-4-hydroxybenzoate, octadecyl 3,5-di-tert-butyl-4-hydroxybenzoate, 2-methyl-4,6-di-tert-butylphenyl 3,5-di-tert-butyl-4-hydroxybenzoate.

[0085] Additional additives suitable for use in the additive component include compounds that promote photopolymerization, such as so-called photosensitizers, which shift or broaden the spectral sensitivity of the composition in which they are incorporated. Photosensitizers include, in particular, aromatic carbonyl compounds such as benzophenone derivatives, thioxanthone derivatives, anthraquinone derivatives and 3-acylcoumarin derivatives, as well as 3-(aroylmethylene)thiazoline, and eosin, rhodamine and erythrosine dyes. Alternatively, non-aromatic carbonyl compounds may be used. An example of a non-aromatic carbonyl is dimethoxyanthracene.

[0086] The curing procedure can be assisted in particular by using additives that produce or promote the production of a colored composition. Such additives include pigments such as titanium dioxide, additives that form free radicals under thermal conditions, such as azo compounds such as 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), triazene, diazosulfide, pentazadiene or peroxy compounds such as hydroperoxide or peroxicarbonate, such as t-butyl hydroperoxide, as described in U.S. Patent No. 4,753,817. Further suitable substances for this purpose include benzopinacol compounds.

[0087] The additive component can include a photoreductive dye, such as a xanthene, benzoxanthene, benzothioxanthene, thiazine, pyronin, porphyrin or acridine dye, and / or a trihalomethyl compound that can be cleaved by radiation. Such additives are described, for example, in U.S. Patent No. 5,229,253.

[0088] Depending on the intended use, other conventional additives may be used. Examples include optical brighteners, fillers, pigments, dyes, wetting agents or leveling aids. Thickly colored coatings can also contain glass microbeads or powdered glass fibers, as described, for example, in U.S. Patent No. 5,013,768.

[0089] In one embodiment, the additive component includes one or more various additives used to improve one or more properties of the primary coating. Such additives include antioxidants (such as Irganox 1035, thiodiethylene bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], or tert-butylhydroquinone), adhesion promoters, inhibitors (such as acrylic acid), photosensitizers, carrier surfactants, tackifiers, catalysts, stabilizers, surface agents, and optical brighteners.

[0090] In a preferred embodiment, the additive component comprises, consists of, or consists essentially of one or more adhesion promoter compounds. The adhesion promoter provides a linkage between the polymer primary coating and the surface of the optical glass fiber. Hydrolyzable silane coupling agents, which are hydrolyzable, are used as glass adhesion promoters. Silane coupling agents are described, for example, in U.S. Patent No. 4,932,750. In one embodiment, the adhesion promoter is a hydrolyzable silane compound containing a mercapto group and / or a plurality of alkoxy groups. Such adhesion promoters are known and are described in U.S. Patent Application No. 20020013383, the relevant portions of which are incorporated herein by reference.

[0091] In one embodiment, the adhesion promoter comprises one or more of γ-mercaptopropyltrimethoxysilane, trimethoxysilylpropyl acrylate, or 3-trimethoxysilylpropane-1-thiol. Alternatively, the silane coupling group can be reacted on the oligomer in the oligomer component; in such a case, the silane coupling group is considered as part of the oligomer component rather than as an additive. Thus, in one embodiment, the adhesion promoter includes oligomeric adhesion promoters, preferably those having urethane groups and acrylate groups. When used, the oligomeric urethane acrylate adhesion promoter preferably contains at least two urethane groups and is a reaction product of a monofunctional telechelic urethane acrylate oligomer containing a telechelic hydroxyl group, preferably by reaction with an isocyanate silane adhesion promoter or a diisocyanate having a hydroxy, mercapto or amino functional silane.

[0092] One or more of the foregoing additives can be used in the composition according to the present invention in any suitable amount, and can be selected alone or in combination with one or more of the types listed herein. In a preferred embodiment, the additive component is present in an amount of about 0 wt% to 20 wt%, or 0 wt% to 10 wt%, or 0 wt% to 5 wt%, or 0.01 wt% to 20 wt%, or 0.01 wt% to 10 wt%, or 0.01 wt% to 5 wt%, or 0.1 wt% to 2 wt% based on the total weight of the composition. According to another embodiment, the additive component is present in an amount of 1 wt% to 20 wt%, or 1 wt% to 10 wt%, or 1 wt% to 5 wt% based on the weight of the entire radiation curable composition.

[0093] As described above, the compositions formulated according to various embodiments of the first aspect can be configured to have certain desirable characteristics. Specifically, such compositions and / or formulations can form cured products that, in addition to having a low amount of volatile diluent, have a sufficiently low elastic modulus value and / or are rapidly curable. This makes such coatings and / or formulations useful for optical fiber coating applications where microbend-induced attenuation resistance and high process speeds are desirable or required. As used herein, a surrogate measure of microbend-induced attenuation is the storage modulus (G'). It is known that a primary coating composition with a lower elastic modulus confers better resistance to microbend-induced attenuation, all other conditions being equal. Further, as used herein, a surrogate measure of cure rate is the time it takes for a particular coating or formulation to reach 30% of its final storage modulus value.

[0094] Accordingly, in various particular further embodiments, an optical fiber primary coating composition according to any of the embodiments of the first aspect, when cured into a film according to the processes and dimensions specified elsewhere herein, is configured to have a storage modulus (G') of less than 600 kPa, or from 1 to 550 kPa, or from 10 to 500 kPa, or less than 300 kPa, or from 1 to 200 kPa, or from 10 to 150 kPa.

[0095] Furthermore, in various other particular further embodiments, an optical fiber primary coating composition according to any of the embodiments of the first aspect, when cured into a film according to the processes and dimensions specified elsewhere herein, is configured such that the time to reach 30% of the increase in storage modulus is less than 1.2 seconds, or less than 1 second.

[0096] The composition and / or formulation of the first aspect preferably further has a viscosity value suitable for use in optical fiber applications and the curing process. Thus, in yet another specific further embodiment, the optical fiber primary coating composition according to any of the embodiments of the first aspect has a viscosity of at least >0.1 Pascal-second (Pa·s), or at least 0.2, or at least 0.5, or at least 1 Pa·s, and / or less than 15 Pa·s, or less than 12, or less than 10 Pa·s; or is configured to have a viscosity of 1 to 15 Pa·s, or 2 to 12 Pa·s, or 3 to 10 Pa·s, where the viscosity is measured at 25°C and a shear rate of 2500 s -1 of.

[0097] A second aspect of the present invention is a method for coating an optical fiber, comprising the steps of providing a glass optical fiber, preferably by drawing the glass optical fiber through a draw tower; applying a primary coating composition onto the surface of the glass optical fiber; optionally, applying a dose of UV light sufficient to at least partially cure the primary coating composition; applying a secondary coating composition onto the primary coating composition; and exposing the primary coating composition and the secondary coating composition to at least one radiation source capable of emitting ultraviolet light and affecting the curing of the primary coating composition and the secondary coating composition to form a cured primary coating on the surface of the optical fiber and a cured secondary coating on the surface of the cured primary coating; wherein the primary coating composition is a composition according to any of the embodiments of the first aspect of the present invention.

[0098] A third aspect of the present invention is a coated optical fiber, comprising: a glass core and a cladding layer that contacts and surrounds the glass core; a coating portion that further includes a primary coating layer that contacts and surrounds the cladding layer; and a secondary coating layer that contacts and surrounds the primary coating layer. According to this aspect, the primary coating layer is a cured product of a radiation-curable composition according to any of the embodiments of the first aspect, and the primary coating and the secondary coating are applied and cured according to any of the embodiments of the second aspect.

[0099] According to one embodiment of the third aspect, the optical fiber includes a core, a cladding, a primary coating that contacts and surrounds an outer annular cladding region, and a secondary coating. According to some embodiments of the third aspect, the core includes pure silica glass (SiO2) or silica glass having one or more dopants that increase the refractive index of the glass core relative to pure undoped silica glass. Suitable dopants for increasing the refractive index of the core include, but are not limited to, GeO2, Al2O3, P2O5, TiO2, ZrO2, Nb2O5, Ta2O5, and / or combinations thereof.

[0100] The cladding layer can include pure silica glass (SiO2), silica glass having one or more dopants that increase the refractive index (e.g., GeO2, Al2O3, P2O5, TiO2, ZrO2, Nb2O5, and / or Ta2O5) such as when the cladding is "up-doped", or silica glass having a dopant that decreases the refractive index such as fluorine when the inner cladding is "down-doped", provided that the maximum relative refractive index [Δ 1MAX of the core is greater than the maximum relative refractive index [Δ 4MAX of the cladding. According to one embodiment, the cladding is also pure silica glass.

[0101] According to some embodiments of the third aspect, the primary coating has an in-situ (or on-fiber) tensile modulus of less than 1.5 MPa, or less than 1.0 MPa, or less than 0.6 MPa, or less than 0.5 MPa, or less than 0.3 MPa, or from 0.15 to 0.8 MPa, and in other embodiments less than 0.2 MPa, which is a typical primary coating. Methods for characterizing the in-situ modulus are well known in the art and are described, inter alia, in U.S. Patent No. 7,171,103 and U.S. Patent No. 6,961,508, each of which is assigned to Covestro (Netherlands) B.V. In one embodiment, the cured primary coating has an in-situ glass transition temperature of less than -35 °C, or less than -40 °C, or less than -45 °C, and in other embodiments less than or equal to -50 °C. A primary coating having a low in-situ modulus reduces microbending, which is a coupling mechanism between the modes propagating in the fiber. The low in-situ glass transition temperature ensures that the in-situ modulus of the primary coating remains low even when the fiber is deployed in a very low temperature environment.

[0102] The primary coating maintains adequate adhesion to the glass fiber during thermal and hydrolytic aging and can be peeled from the glass fiber (if necessary) for splicing purposes. The primary coating typically has a thickness in the range of 20 to 50 μm (e.g., about 25 or 32.5 μm), and for 200 μm fibers, a thinner thickness in the range of 15 to 25 μm. In other embodiments, the primary coating preferably has a thickness of less than about 40 μm, more preferably from about 20 to about 40 μm, and most preferably from about 20 to about 30 μm.

[0103] The secondary coating contacts and surrounds the primary coating. The secondary coating is, for example, a polymerization product of a coating composition in which the molecules are highly crosslinked during polymerization. According to one embodiment, the secondary coating can have an in-situ tensile modulus of more than 800 MPa, or more than 1110 MPa, or more than 1300 MPa, or more than 1400 MPa, or more than 1500 MPa. The secondary coating having a high in-situ modulus reduces microbending, which is a coupling mechanism between modes propagating within the fiber.

[0104] According to other embodiments, the secondary coating has a high in-situ modulus (e.g., more than about 800 MPa at 25 °C) and a high T g (e.g., more than about 50 °C). In other preferred embodiments, the in-situ secondary modulus is from about 1000 MPa to about 8000 MPa, more preferably from about 1200 MPa to about 5000 MPa, and most preferably from about 1500 MPa to about 3000 MPa. The in-situ T g of the secondary coating is preferably from about 50 °C to about 120 °C, more preferably from about 50 °C to about 100 °C. In one embodiment, the secondary coating has a thickness of less than about 40 μm, more preferably from about 20 to about 40 μm, and most preferably from about 20 to about 30 μm.

[0105] Materials suitable for use in the outer (or second) coating material, as well as considerations regarding the selection of these materials, are well known in the art and are described, for example, in U.S. Pat. Nos. 4,962,992 and 5,104,433 to Chapin. As an alternative to these, high modulus coatings have also been obtained using a low oligomer content coating system, as described in U.S. Pat. Nos. 6,775,451 to Botelho and 6,689,463 to Chou. Further, as described in U.S. Patent Application Publication No. 20070100039 by Schissel et al., non-reactive oligomer components have been used to achieve high modulus coatings. The secondary coating may also contain ink, as is well known in the art. In such a case, the secondary coating may be referred to as a "colored secondary coating".

[0106] The coated optical fiber may alternatively comprise one or more additional layers disposed on the secondary layer. Most notably, such a layer comprises an independent "ink" layer that is applied and cured separately from the secondary coating. Other multilayer coating systems are known, for example, as disclosed in WO2017173296.

[0107] Methods of formulating primary and secondary coatings for fibers as described above, as well as typical optical fiber coatings for inks and matrix materials to be cured using a broadband UV lamp, are known in the art. A good discussion of this technology and related chemistry and test methods can be found in Section 4.6 through the end of Chapter 4 of "Specialty Optical Fibers Handbook" by A. Mendez and T. F. Morse, published by Elsevier, (C) Elsevier Inc. 2007.

[0108] In embodiments of the second aspect of the present invention, any type of optical fiber can be used. However, in a preferred embodiment, the coated optical fiber has a mode field diameter of 8 - 10 μm at a wavelength of 1310 nm, or 9 - 13 μm at a wavelength of 1550 nm, and / or an effective cross-sectional area of 20 - 200 μm 2 . Such fibers can be single-mode fibers and / or large effective cross-sectional area fibers, considering the expected demand for coating processes for these fibers that utilize higher line speeds or processing speeds. However, other fiber types such as multimode fibers can be used as well.

[0109] A fourth aspect of the present invention is an optical fiber cable, where the optical fiber comprises at least one optical fiber according to any embodiment of the third aspect of the present invention, and / or the optical fiber is a cured product of the composition according to the first aspect of the present invention, and / or the optical fiber is coated according to the second aspect of the present invention.

[0110] The improved compositions of the present invention (and the coated optical fibers produced therefrom) can be formulated by the selection of the components specified above herein, and further, by following the formulation guidelines herein, as well as by extrapolating from the general approaches taken in the embodiments illustrated in the following examples, can be readily adjusted by those skilled in the art to which the present invention pertains. The following such examples further illustrate the invention, but of course should in no way be construed as limiting its scope.

Examples

[0111] These examples illustrate embodiments of the present invention. Table 1 describes the various components of the compositions used in this example. Table 2 describes the relative amounts of the reagents described in Table 1 that were used to synthesize the oligomers used in this example. Table 3 provides an overview of the further analysis of the oligomers so characterized in Table 2, and the methods for analyzing such oligomers are further described hereinbelow. Table 1 - Formulation Components

[0112]

Table 1

[0113] Synthesis of Oligomers 1 - 16 First, the reactor was purged with dry, lean air. Next, specific amounts from Table 2 below were charged to the reactor (equipped with a stirrer, air inlet, dropping funnel, and condenser): first, (1) BHT (e.g., 1.32 parts for oligomer 1); then, (2) the applicable isocyanate (e.g., 86.62 parts of TDI for oligomer 1), followed by (3) acrylic acid (e.g., 0.09 parts for oligomer 1). After charging, the reactor was heated to 45 °C. Next, half of the designated DBTDL catalyst (e.g., 0.06 g of DBTDL), followed by a hydroxyl-functional end cap (e.g., 57.87 parts of HEA in oligomer 1), were charged to the reactor with stirring. After waiting for 1 hour until the reaction started, the temperature was raised to 60 °C. At 60 °C, a hydroxyl-functional or thiol-functional backbone component (e.g., HO-PPG 1000 -OBu at 661.01 g per oligomer 1) and the second part of the catalyst (e.g., 0.07 g) were added, after which the reaction temperature was raised to 85 °C and then maintained for an additional 2 hours. After this 2-hour reaction time, the isocyanate (NCO) content was measured with a potentiometric titration apparatus and confirmed to be less than 0.1% relative to the total weight of the composition. If the isocyanate content did not fall below this value, the mixture was returned to the reaction chamber in additional increments of 15 minutes (again at 85 °C), and this process was repeated and checked until the isocyanate content was within the desired range. Finally, the resulting synthetic oligomer was slowly cooled and discharged for use in the experiments described elsewhere in this specification. The resulting oligomers had an idealized structure as shown in Table 2, and oligomer 1 had the following idealized structure (where "T" represents the reaction product of a diisocyanate compound, "PPG 1000 " represents the reaction product of polyol PPG 1000 and "H-" represents the reaction product of the hydroxy-functional end capper HEA):

[0114] [Chemical formula 1] H-T-PPG 1000 -OH

[0115] Note on Oligomer 16: One-pot synthesis was applied to obtain two oligomers: 80% H-T-PDMS3000-OH (a) + 20% H-T-PDMS3000-T-H (b) Oligomer 17 This oligomer was prepared using 95.32 parts of Acclaim 6320N, 6.15 parts of HEA, 503 parts of Acclaim 8200 N, 18.97 parts of TDI, 0.3 parts of DBTDL, 0.824 parts of BHT, 0.29 parts of acrylic acid, and 190.4 parts of SR489D as described in WO2021021971 (Oligomer 1 in WO2021021971). The idealized structure was as follows (where "T" represents the reaction product of the diisocyanate compound TDI, "-H" represents the reaction product of the hydroxy-functional endcapper HEA, and "PPG 6000 (triol)" represents the reaction product of the polyol Acclaim 6320N):

[0116] [Chemical Formula 2] PPG 6000 (triol)-(T-PPG 8000 -T-H)3

[0117] Oligomer 18 First, the reactor was purged with dry dilute air. Next, 0.28 g of BHT, 150.77 g of oligomer 3 (H-T-PPG4000-OH), and 0.02 g of acrylic acid were placed into a reactor (equipped with a stirrer, air inlet, dropping funnel, and condenser). After filling, the reactor was heated to 75 °C. Then, 0.03 g of DBTDL was added, followed by 8.65 g of 3-(triethoxysilyl)propyl isocyanate, and then the mixture was stirred for an additional 2 hours. After this 2-hour reaction time, the isocyanate (NCO) content was measured using a potentiometric titration apparatus and confirmed to be less than 0.1% relative to the total weight of the composition. If the isocyanate content did not fall below this value, the mixture was returned to the reaction chamber in additional increments of 30 minutes (again at 85 °C), and this process was repeated and checked until the isocyanate content was within the desired range. Finally, the resulting synthetic oligomer was slowly cooled and discharged for use in the experiments described elsewhere in this specification. The resulting oligomer had the following idealized structure (where "T" represents the reaction product of a diisocyanate compound and "H-" represents the reaction product of a hydroxy-functional endcapper HEA):

[0118] [Chemical Formula 3] H-T-PPG 4000 -OC(O)NHC3H5Si(OC2H5)3

[0119] Oligomer 19 First, a 500 ml reactor was purged with dry dilute air. Next, 0.5 part of BHT, 0.03 part of acrylic acid, and 300 parts of Acclaim 4200 were charged into a reactor (equipped with a stirrer, air inlet, dropping funnel, and condenser). After filling, the reactor was heated to 85 °C and 0.06 part of DBTDL was added at that temperature. Next, 10.07 parts of 2-isocyanatoethyl acrylate were slowly added with stirring and maintained at 85 °C for an additional 2 hours, after which the NCO content was less than 0.1%. The resulting oligomer had the following idealized structure (where "A" represents an acrylate group, i.e., CH2CHCO2):

[0120] [Chemical formula 4] A-C2H4NHC(O)O-PPG 4000 -OH

[0121] 138.87 g of this intermediate oligomer (A-C2H4NHC(O)O-PPG 4000 -OH) and 7.3 g of 3-(triethoxysilyl)propyl isocyanate were used to prepare the oligomer in the same manner as described above for oligomer 18. The resulting oligomer had the following idealized structure (wherein "A" represents an acrylate group (i.e., CH2CHCO2)):

[0122] [Chemical formula 5] A-C2H4NHC(O)O-PPG 4000 -OC(O)NHC3H6Si(OC2H5)3

[0123] Table 2 - Oligomer Synthesis

[0124]

Table 2

[0125] Table 3 - Characterization of Further Oligomers Unless otherwise specified, all units are in kilodaltons.

[0126]

Table 3

[0127] SEC Property Evaluation

[0128] After synthesizing various reactive oligomers, they were evaluated by size exclusion chromatography (SEC) in accordance with D5296-11: "Standard Test Method for Molecular Weight Averages and Molecular Weight Distribution of Polystyrene by High Performance Size-Exclusion Chromatography", ASTM International, West Conshohocken, PA, (2011). Further, ASTM norm D 5226-98: "Standard Practice for Dissolving Polymer Materials", ASTM International, West Conshohocken, PA, (2010) was used to facilitate the definition of a solvent suitable for polymer analysis.

[0129] Specifically, all size exclusion chromatography measurements were performed on a Waters APC (Advanced Polymer Chromatography) system equipped with an RI detector, a Wyatt microDawn multi-angle light scattering device, and a Wyatt microViscoStar capillary bridge differential pressure viscometer. For chromatographic separation, columns: 4.6x76mm, Acquity APC XT 450 2.5μm, 125 2.5μm, 45 1.7μm were used. The detector and columns were operated at 40 °C. Before performing SEC, each polymer was dissolved in tetrahydrofuran (THF) containing 1 wt% acetic acid at a concentration in the range of 1.0 - 1.5 mg / ml. This THF solution was also used as the eluent in the SEC analysis at a flow rate of 0.5 ml / min.

[0130] After dissolution, the molar mass and molar mass distribution were determined using the above triple detection method that uses refractive index, differential viscosity, and right-angle light scattering signal. For the calculation of the molecular weight average and molar mass distribution, a refractive index increment (dn / dc) of about 0.07 ml / g was used. Specifically, the dn / dc values of oligomers 1 to 19 were determined accordingly and reported in Table 3 of this specification in units of milliliters / gram. The refractive index increment and molecular weight average, as well as the molar mass distribution, were determined by integration of the total refractive index chromatogram. The IV-DP signal was further used to set the integration limit. The recovery rate of the sample from the column was 95 to 105%, which is a typical value obtained by size exclusion chromatography.

[0131] Using the above method, the values of Mn, Mw, Mz, and dn / dc were recorded and reported. Oligomer Tg

[0132] The glass transition temperature (Tg) of the synthesized oligomers was measured with a Mettler Toledo DSC3+ differential scanning calorimeter. A temperature range of -80 °C to 80 °C was adopted. As a result, only Tg values higher than -70 °C were reliably determined. The evaluation was performed using the Stare software with the first derivative of the second heating curve using a heating rate of 10 °C / min. Formulations 1 to 42

[0133] Each of the formulations described in Table 4 below was prepared by a conventional method by using a 50 ml mixing cup suitable for use with Speedmixer™. Specifically, 1 part by weight of the photoinitiator BAPO and 0.25 part by weight of Irganox 1520L were added to the amounts of the components specified in Table 4 below to obtain a total of 10 g for each formulation. Then, the cup was closed and mixed vigorously in a Speedmixer™ DAC150FVZ for 30 seconds, stopped, and mixed again for 30 seconds in the same manner.

[0134] These samples were each tested for the viscosity of the respective formulation, T 30%,弾性率最大値, and to determine the maximum G’ respectively, tests were conducted according to the methods described below. The viscosity values are reported in Pascal seconds (Pa·s), rounded to two decimal places, and T 30%,弾性率最大値 is expressed in seconds and rounded to two decimal places. The maximum G’ is reported in kilopascals (kPa) and rounded to the nearest integer unit. The values of these measured properties are reported in Table 4 below. Viscosity

[0135] The viscosity of the formulation was measured with a Brookfield CAP 1000 at 750 rpm and recorded after 30 seconds. The measurements were performed three times at 25 °C and a shear rate of 2500 s -1 (The average value is shown in Table 4 below). Measurement of the maximum elastic modulus (G’) and T 30%,弾性率 最大 Value measurement The value of the maximum elastic modulus (G’) was determined according to the following procedure described herein. The hardware / devices used in this procedure were as follows: Rheometer + accessories · ARES G2 - Rheometer (manufacturer: TA Instruments) · APS Temperature Control Device (Advanced Peltier System) · APS Standard Flat Plate (lower geometry) · ARES G2 UV Curing Accessory (upper plate fixture, UV light shielding back & access door, collimating optical lens) · Φ20 mm acrylic plate, Φ with UV curing option upper plate fixture (upper geometry) · Silver line UV radiometer, UV light sensor (not calibrated), UV sensor geometry, and disposable plate holder UV light source etc. · Omnicure LX500 combined with a 385 nm LED and a mounted 8 mm lens · Moeller Easy 412 - DC - TC control relay (trigger box) · UV Power Puck II (Electronic Instrumentation & Technology, Calibrated)

[0136] Next, the above-mentioned hardware was set up and arranged as follows. First, UV curing measurements were performed with an ARES G2 rheometer (TA Instruments). The rheometer was equipped with an APS temperature control device, an APS Standard Flat Plate as the lower geometry, and an ARES G2 UV curing option. The upper geometry used was the upper plate fixture from the ARES G2 UV curing option combined with a 20 mm diameter acrylic plate. As the UV light source, an Omnicure LX500 spot curing system was used in combination with a 385 nm LED (8 mm lens). Next, the 385 nm LED was inserted into the collimating optical lens of the ARES G2 UV curing accessory. The collimating lens was fixed to the light shield, aligned with the upper UV geometry mirror, and the alignment screws were tightened. To accommodate the 385 nm UV-LED, the diameter of the original 5 mm optical guide holder part of the collimating lens was increased to 12 mm.

[0137] Next, the Omnicure LX500 spot curing system was connected to the DIGITAL I / O connector of the ARES G2 via a Moeller Easy 412-DC-TC Control Relay. The control relay functioned as a trigger box for the UV light source. The trigger delay time was set to 1.5 seconds, which means that the 385 nm UV-LED was automatically switched on with a 1.5-second delay after the start of data collection of the modulus measurement on the ARES G2. The light intensity was set to 95%, and the duration of the UV light was fixed at 128 seconds.

[0138] Alignment of UV light: Alignment was performed before the installation of the APS temperature control unit. The UV sensor geometry was attached to a disposable plate holder and installed as the lower geometry. The UV light sensor connected to the Silverline UV radiometer was placed in a hole outside the UV sensor geometry. The upper geometry was placed on top of the UV light sensor by applying an axial force of approximately 100 grams. Then, the light intensity was measured at four positions by rotating the lower geometry by approximately 90° between successive measurements. To achieve an equal light distribution as much as possible at each point, the alignment of the collimating lens was adjusted using the alignment screws on the light shield. The difference in light intensity at the four different positions was maintained below 10%.

[0139] Measurement of light intensity: Before the RT-DMA measurement, the UV intensity was measured using a calibrated UV Power Puck II. To achieve this, the sensor of the UV Power Puck II was placed directly below the surface of the 20 mm acrylic plate in the upper plate fixture with the surface of the acrylic plate completely covering the sensor surface (distance < 0.5 mm). Next, the Omnicure LX500 UV source (intensity value set to 95%) was manually turned on for 10 seconds. During these 10 seconds, the UVA2 intensity (i.e., radiation between wavelengths of 380 - 410 nm) was measured using the UV Power Puck II device. The measured UVA2 intensity was determined to be between 60 - 70 mW / cm 2 and the actual value was recorded as 67 mW / cm 2 .

[0140] Determination of the actual delay time: When starting the measurement, there was a delay between the start of data sampling and the start of UV irradiation. In the settings of the Moeller Easy 412-DC-TC Control Relay, the delay was set to 1.5 seconds, which means that UV irradiation started 1.5 seconds after the start of data sampling.

[0141] Using light-dependent resistance (LDR) and an oscilloscope (PicoScope 3424), the actual delay time of 1.519 seconds was measured. The delay time of 1.519 seconds was the average value of 10 individual measurements with a standard deviation of 0.004 seconds.

[0142] RT-DMA measurement: Next, RT-DMA UV curing measurements were performed using an ARESG2 rheometer, an APS Flat Plate, and an ARESG2 UV curing accessory setup paired with an Advanced Peltier System as the temperature control device. As the UV light source, a 385 nm LED equipped with an 8 mm lens connected to an Omnicure LX500 was used.

[0143] Sample loading: Before loading each sample, the temperature of the bottom plate was set to 50 °C. When it reached 50 °C, an axial force of 200 - 400 g was applied to the surface of the upper plate (acrylic plate with a thickness of 20 mm) to make it contact the lower plate (with a gap of 0 mm), and the upper parallel plate was equilibrated to the set temperature of 50 °C. The system further equilibrated the temperature for at least 5 minutes after the first contact. Next, a zero - fixture procedure was performed according to a well - known method to determine the gap = 0 position. After determining the gap = 0 position, the upper plate was moved to a position 10 mm away. Next, a part of each sample was transferred to the center of the lower plate with the tip of a small spatula, and then the upper geometry was lowered to a position with a gap = 0.120 mm. The amount of the sample had to be sufficient to ensure that an excess amount was extruded outside the gap covering the entire circumference of the upper parallel plate after the upper geometry was lowered to the reduced gap. Next, the extra sample that had moved outside the gap was removed, and the upper geometry was further lowered to the measurement position (with a gap = 0.100 mm). With the sample loaded at the measurement position, the temperature of the sample was equilibrated to 50 °C. Finally, when the sample temperature was stably measured between 49.90 - 50.10 °C, the trigger box (Moeller Easy 412 - DC - TC) was activated, and the measurement process was started by using the interface and interconnection provided by the TRIOS software package.

[0144] Measurement: The actual UV - curing RT - DMA measurement was a so - called "high - speed sampling" measurement performed at 50 °C. That is, it was a vibration high - speed sampling performed at 50 °C for 128 seconds with a strain of 1%, a rotation speed of 52.36 rad / s, and a measurement frequency of 50 points per second (i.e., the interval between consecutive measurement points was 0.020 seconds).

[0145] Subsequently, the measurement was started via the start button of the TRIOS software. When data sampling was initiated, the rheometer sent a signal to the control relay, which in turn activated the Omnicure LX500 UV light source to irradiate each sample with a delay of 1.519 seconds after the start of data sampling. As described above, the samples were irradiated with UV light at 385 nm (intensity 60 - 70 mW / cm 2 ) during the 128 - second high - speed sampling data collection. After the measurement, the TRIOS data file was exported to Microsoft Excel. Then, the sample was taken out, and the plate was thoroughly washed with ethanol, after which the next sample was loaded.

[0146] Data analysis: As described above, the TRIOS data was exported to Microsoft Excel. Graphs were plotted using Excel, and various parameters were calculated for the characterization of the curing speed performance of the tested formulations as described below. The graphs included a graph corresponding to the storage modulus (G’) as a function of UV time (the UV time was calculated by subtracting the delay time (1.519 s) from the actual time for each data point), and the relative storage modulus (rel G’) as a function of UV time (rel G’ was calculated by the quotient of the G’ value measured at a specific UV time and the maximum G’ value obtained during the curing measurement). The observed maximum value of the G’ graph was determined by taking the average of the G’ values between 110 - 120 seconds and was reported in the column headed by "Maximum G’" in Table 4 below. For samples that did not cure completely during the test time, the indication "NFC" was placed in this column, indicating that the maximum G’ could not be achieved with the adopted test procedure and time limit.

[0147] On the other hand, the characteristic parameters included (1) the time until 30% of the total increase in the storage modulus (G’) was reached, and (2) the average G’ of 110 - 120 s (the average storage modulus values of six data points towards the end of the curing measurement). The results of (1) for each formulation were reported in the title column of T 30%,弾性率 最大 in Table 4 below. Table 4 All amounts are in parts by weight.

[0148]

Table 4

[0149] Discussion of Results

[0150] As can be seen, the compositions according to various aspects of the present invention tend to have properties that make them particularly suitable for use in optical fiber coating applications, particularly as primary optical fiber coatings. First, compositions that contain little or no reactive diluent (EOEOA, DMA, and / or nVC as used in the above examples) are clearly more preferred for use in optical fiber coating applications in that, all other conditions being the same, the volatile content is minimized.

[0151] Furthermore, compositions having such a low volatile content can be configured in various different ways so as to exhibit further suitability for use in optical fiber coating applications, particularly in terms of cure speed (measured at a low T 30%,弾性率 最大 value, particularly less than 1.2 seconds, more preferably less than 1.0 second), low elastic modulus (measured at a low G value, particularly less than 600 kPa, more preferably less than 500 kPa, more preferably less than 400 kPa, more preferably less than 300 kPa), and / or low viscosity (particularly less than 9 Pascal seconds, more preferably less than 5 Pascal seconds).

[0152] The foregoing effects are demonstrated using various oligomer types, amounts, combinations, and diluents.

[0153] Unless otherwise specified, the term weight % means the amount by mass of a particular component relative to the total liquid radiation curable formulation in which it is incorporated.

[0154] In the context of describing the present invention (especially in the context of the appended patent claims), the use of the terms "a", "an", and "The" and similar referents should be construed to include both the singular and the plural, unless otherwise indicated herein or clearly inconsistent with the context. The terms "comprising", "having", "including", and "containing" are to be construed as open-ended terms (i.e., meaning "including but not limited to") unless otherwise specified. The recitation of numerical ranges herein is merely intended to serve as a shorthand for referring individually to each value falling within the range, and each value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or clearly inconsistent with the context. Any examples or exemplary language used herein (e.g., "such as") are merely intended to better illustrate the invention and are not intended to limit the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.

[0155] Preferred embodiments of the present invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of these preferred embodiments may become apparent to those skilled in the art upon reading the above description. The inventors expect those skilled in the art to appropriately apply such variations, and the invention is contemplated to be practiced in ways other than those specifically described herein. Accordingly, the present invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Further, all possible combinations of the above-described elements in all possible variations are included in the present invention unless otherwise indicated herein or clearly inconsistent with the context. Although the present invention has been described in detail with reference to its particular embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the claimed invention.

Claims

1. A primary coating composition for optical fibers, wherein the weight of the entire primary coating composition is: (a) one or more oligomers which are reaction products of at least 0.01% by weight of (iii) a hydroxyl-functional end capper further comprising an ethylenically unsaturated moiety, (ii) an isocyanate compound, and (i) a hydroxyl-functional or thiol-functional main chain compound; Here, the molar ratio of the number of isocyanate groups in (ii) to the number of hydroxyl and thiol groups in (i) is 1.0 or less; (b) Optionally, one or more urethane (meth)acrylate oligomers other than those in (a); (c) Optionally, a reactive diluent monomer; (d) Photoinitiator; (e) Optionally, one or more additives Includes, Herein, the total amount of (a) + (b) is 70% to 99% by weight, which is the primary coating composition for optical fibers.

2. The optical fiber primary coating composition according to claim 1, wherein, in the absence of (b), one or more oligomers described in (a) have at least two ethylenically unsaturated groups, more preferably two ethylenically unsaturated groups.

3. The optical fiber primary coating composition according to claim 1, wherein one or more oligomers described in (a) are present in an amount of more than 1% by weight, preferably more than 5% by weight, preferably more than 10% by weight, preferably more than 20% by weight, preferably more than 30% by weight, and preferably more than 40% by weight.

4. The optical fiber primary coating composition according to claim 1, wherein one or more oligomers described in (a) are present in an amount of 95% by weight or less, preferably 90% by weight or less, preferably 80% by weight or less, and preferably 70% by weight or less.

5. The optical fiber primary coating composition according to claim 1, wherein the acrylate content in the composition is 2.50 mol / kg or less, preferably 2.00 mol / kg or less, more preferably 1.50 mol / kg or less, more preferably 1.20 mol / kg or less, more preferably 1.00 mol / kg or less, and more preferably 0.80 mol / kg or less.

6. The optical fiber primary coating composition according to claim 1, wherein the urethane content in the composition is 0.90 mol / kg or less, preferably 0.70 mol / kg or less.

7. The optical fiber primary coating composition according to claim 1, wherein the urethane content in the composition is 0.25 mol / kg or more, or 0.30 mol / kg or more, or 0.31 mol / kg or more, or 0.35 mol / kg or more, or 0.40 mol / kg or more, or 0.45 mol / kg or more, or 0.50 mol / kg or more.

8. The optical fiber primary coating composition according to claim 1, wherein the total acrylate content in oligomers (a) and (b) is 0.05 mol / kg oligomer (a) + (b) to 0.80 mol / kg oligomer (a) + (b).

9. The optical fiber primary coating composition according to claim 1, wherein the oligomers described in (a) and (b) are present in an amount of 80% by weight or more and 96% by weight or less, and (i) comprises a polyether, polyester, polybutadiene, polycarbonate, or silicone portion.

10. The optical fiber primary coating composition according to claim 1, wherein the hydroxy-functional or thiol-functional main chain compound (i) comprises a polyether polyol, preferably polypropylene glycol.

11. The optical fiber primary coating composition according to claim 1, wherein the molar ratio of the number of isocyanate groups in (ii) to the number of hydroxyl groups and thiol groups in (i) is 2 / 3 or more.

12. The optical fiber primary coating composition according to claim 1, wherein the oligomer described in (a) has 1.8 to 2.2 urethane bonds, and / or one or more oligomers described in (a) have a diblock or triblock structure.

13. The optical fiber primary coating composition according to claim 1, wherein one or more oligomers described in (a) have a number average molecular weight (Mn) of 1,000 g / mol to 10,000 g / mol, preferably 1,200 g / mol to 9,000 g / mol.

14. The optical fiber primary coating composition according to claim 1, wherein one or more oligomers described in (a) end with a hydroxyl group at one end.

15. The optical fiber primary coating composition according to claim 1, wherein the (iii) hydroxyl-functionalized end capper further comprises one or two ethylenically unsaturated moieties, preferably the (iii) hydroxyl-functionalized end capper further comprises one ethylenically unsaturated moiety.

16. (i) The optical fiber primary coating composition according to claim 1, wherein the hydroxyl-functionalized main chain compound comprises at least two hydroxyl groups, or at least three hydroxyl groups, or four hydroxyl groups.

17. The optical fiber primary coating composition according to claim 1, wherein one or more oligomers described in (a) comprises a reaction product of a single PPG diol as (i); a single diisocyanate compound as (ii); and a hydroxyl-functionalized (meth)acrylate compound as (iii).

18. The optical fiber primary coating composition according to claim 1, wherein in one or more oligomers (a), the molar ratio of isocyanate groups in (ii) to the number of hydroxyl groups in (i) is equal to 1.

0.

19. The optical fiber primary coating composition according to claim 1, wherein (ii) comprises, essentially consists of, or comprises isophorone diisocyanate, 2,4-isomerized 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 a combination thereof.

20. The optical fiber primary coating composition according to claim 1, wherein (iii) comprises, essentially consists of, or comprises hydroxyethyl methacrylate, hydroxyethyl acrylate, 2-hydroxypropyl methacrylate, 2-hydroxypropyl acrylate, 3-hydroxypropyl methacrylate, 3-hydroxypropyl acrylate, 4-hydroxybutyl methacrylate, 4-hydroxybutyl acrylate, caprolactone methacrylate, caprolactone acrylate, glycerol acrylate methacrylate, glycerol dimethacrylate, glycerol diacrylate, or a combination thereof.

21. The optical fiber primary coating composition according to claim 1, wherein one or more urethane (meth)acrylate oligomers (b) are present in an amount of 29.95% by weight or less.

22. One or more urethane (meth)acrylate oligomers (b) also include the reaction product of (i) a hydroxyl-functional main chain compound, (ii) an isocyanate compound, and (iii) a hydroxyl-functional end capper. Here, in the urethane (meth)acrylate oligomer (b), the molar ratio of the number of isocyanate groups in (ii) to the number of hydroxyl groups in (i) is greater than 1.0, and more preferably about 1.5 to about 2.

0. The optical fiber primary coating composition according to claim 1.

23. The optical fiber primary coating composition according to claim 22, wherein, for the oligomer described in (b), the molar ratio of the number of isocyanate groups in (ii) to the number of hydroxyl groups and thiol groups in (i) and (iii) is equal to 1.0.