Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C271/00—Derivatives of carbamic acids, i.e. compounds containing any of the groups, the nitrogen atom not being part of nitro or nitroso groups
  • C07C271/06—Esters of carbamic acids
  • C07C271/08—Esters of carbamic acids having oxygen atoms of carbamate groups bound to acyclic carbon atoms
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C271/00—Derivatives of carbamic acids, i.e. compounds containing any of the groups, the nitrogen atom not being part of nitro or nitroso groups
  • C07C271/06—Esters of carbamic acids
  • C07C271/08—Esters of carbamic acids having oxygen atoms of carbamate groups bound to acyclic carbon atoms
  • C07C271/10—Esters of carbamic acids having oxygen atoms of carbamate groups bound to acyclic carbon atoms with the nitrogen atoms of the carbamate groups bound to hydrogen atoms or to acyclic carbon atoms
  • C07C271/20—Esters of carbamic acids having oxygen atoms of carbamate groups bound to acyclic carbon atoms with the nitrogen atoms of the carbamate groups bound to hydrogen atoms or to acyclic carbon atoms to carbon atoms of hydrocarbon radicals substituted by nitrogen atoms not being part of nitro or nitroso groups
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C271/00—Derivatives of carbamic acids, i.e. compounds containing any of the groups, the nitrogen atom not being part of nitro or nitroso groups
  • C07C271/06—Esters of carbamic acids
  • C07C271/08—Esters of carbamic acids having oxygen atoms of carbamate groups bound to acyclic carbon atoms
  • C07C271/24—Esters of carbamic acids having oxygen atoms of carbamate groups bound to acyclic carbon atoms with the nitrogen atom of at least one of the carbamate groups bound to a carbon atom of a ring other than a six-membered aromatic ring
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C271/00—Derivatives of carbamic acids, i.e. compounds containing any of the groups, the nitrogen atom not being part of nitro or nitroso groups
  • C07C271/06—Esters of carbamic acids
  • C07C271/08—Esters of carbamic acids having oxygen atoms of carbamate groups bound to acyclic carbon atoms
  • C07C271/26—Esters of carbamic acids having oxygen atoms of carbamate groups bound to acyclic carbon atoms with the nitrogen atom of at least one of the carbamate groups bound to a carbon atom of a six-membered aromatic ring
  • C07C271/28—Esters of carbamic acids having oxygen atoms of carbamate groups bound to acyclic carbon atoms with the nitrogen atom of at least one of the carbamate groups bound to a carbon atom of a six-membered aromatic ring to a carbon atom of a non-condensed six-membered aromatic ring
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F299/00—Macromolecular compounds obtained by interreacting polymers involving only carbon-to-carbon unsaturated bond reactions, in the absence of non-macromolecular monomers
  • C08F299/02—Macromolecular compounds obtained by interreacting polymers involving only carbon-to-carbon unsaturated bond reactions, in the absence of non-macromolecular monomers from unsaturated polycondensates
  • C08F299/022—Macromolecular compounds obtained by interreacting polymers involving only carbon-to-carbon unsaturated bond reactions, in the absence of non-macromolecular monomers from unsaturated polycondensates from polycondensates with side or terminal unsaturations
  • C08F299/024—Macromolecular compounds obtained by interreacting polymers involving only carbon-to-carbon unsaturated bond reactions, in the absence of non-macromolecular monomers from unsaturated polycondensates from polycondensates with side or terminal unsaturations the unsaturation being in acrylic or methacrylic groups
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G18/00—Polymeric products of isocyanates or isothiocyanates
  • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
  • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
  • C08G18/67—Unsaturated compounds having active hydrogen
  • C08G18/671—Unsaturated compounds having only one group containing active hydrogen
  • C08G18/672—Esters of acrylic or alkyl acrylic acid having only one group containing active hydrogen
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G18/00—Polymeric products of isocyanates or isothiocyanates
  • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
  • C08G18/70—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the isocyanates or isothiocyanates used
  • C08G18/72—Polyisocyanates or polyisothiocyanates
  • C08G18/74—Polyisocyanates or polyisothiocyanates cyclic
  • C08G18/75—Polyisocyanates or polyisothiocyanates cyclic cycloaliphatic
  • C08G18/751—Polyisocyanates or polyisothiocyanates cyclic cycloaliphatic containing only one cycloaliphatic ring
  • C08G18/752—Polyisocyanates or polyisothiocyanates cyclic cycloaliphatic containing only one cycloaliphatic ring containing at least one isocyanate or isothiocyanate group linked to the cycloaliphatic ring by means of an aliphatic group
  • C08G18/753—Polyisocyanates or polyisothiocyanates cyclic cycloaliphatic containing only one cycloaliphatic ring containing at least one isocyanate or isothiocyanate group linked to the cycloaliphatic ring by means of an aliphatic group containing one isocyanate or isothiocyanate group linked to the cycloaliphatic ring by means of an aliphatic group having a primary carbon atom next to the isocyanate or isothiocyanate group
  • C08G18/755—Polyisocyanates or polyisothiocyanates cyclic cycloaliphatic containing only one cycloaliphatic ring containing at least one isocyanate or isothiocyanate group linked to the cycloaliphatic ring by means of an aliphatic group containing one isocyanate or isothiocyanate group linked to the cycloaliphatic ring by means of an aliphatic group having a primary carbon atom next to the isocyanate or isothiocyanate group and at least one isocyanate or isothiocyanate group linked to a secondary carbon atom of the cycloaliphatic ring, e.g. isophorone diisocyanate
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G18/00—Polymeric products of isocyanates or isothiocyanates
  • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
  • C08G18/70—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the isocyanates or isothiocyanates used
  • C08G18/72—Polyisocyanates or polyisothiocyanates
  • C08G18/74—Polyisocyanates or polyisothiocyanates cyclic
  • C08G18/76—Polyisocyanates or polyisothiocyanates cyclic aromatic
  • C08G18/7614—Polyisocyanates or polyisothiocyanates cyclic aromatic containing only one aromatic ring
  • C08G18/7621—Polyisocyanates or polyisothiocyanates cyclic aromatic containing only one aromatic ring being toluene diisocyanate including isomer mixtures
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D175/00—Coating compositions based on polyureas or polyurethanes; Coating compositions based on derivatives of such polymers
  • C09D175/04—Polyurethanes
  • C09D175/14—Polyurethanes having carbon-to-carbon unsaturated bonds
  • C09D175/16—Polyurethanes having carbon-to-carbon unsaturated bonds having terminal carbon-to-carbon unsaturated bonds
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
  • G02B1/04—Optical elements characterised by the material of which they are made; Optical coatings for optical elements made of organic materials, e.g. plastics
  • G02B1/045—Light guides
  • G02B1/048—Light guides characterised by the cladding material

Definitions

• the present invention relates to a UV-curable coating composition which provides upon curing a coating layer having improved water resistance, and to an optical fiber comprising the coating layer.
• Optical fiber used in the fields of electronics, information handling, and telecommunications is composed of quartz glass having a low impact strength, which is coated to minimize the fiber distortion or photosignal loss.
• Such coating is required to have properties that minimize undesirable effects caused by the external environmental changes, in particular, water penetration, and also to impart improved tensile strength and other properties to the quartz fiber, without causing deterioration of the optical signal.
• a composition containing organosiloxane is known to provide a coating that meets the above-mentioned requirements, which has a low glass transition temperature and good hydrophobicity (U.S. Pat. Nos. 4,780,486; 4,848,869 and 4,889,901).
• a fluorine- substituted acrylate composition provides improved hydrophobicity and thermal stability (U.S. Pat. No. 4,687,295).
• this composition is not completely compatible with a non-fluoride organic composition, which makes its application limited, and its manufacturing cost is high.
• U.S. Pat. No. 4,973,611 discloses an optical fiber coating having a low glass transition temperature and good water resistance which comprises an alkylene oxides-containing monofunctional (meth)acrylate.
• U.S. Pat. Nos. 4,246, 379 and 5,639,846 describe a coating composition comprising a urethane acrylate oligomer having a hydroxy(meth)acrylate monomer end group containing a small amount of alkylene oxide moieties.
• the hydroxy(meth)acrylate monomer must be introduced into the oligomer to attain a low glass transition temperature.
• the physical properties of the coating layer obtained therefrom undergo gradual deterioration during a long-term use under severe external environments.
• UV- curable coating composition which, upon curing, provides a coating layer or film having improved physical properties in terms of water resistance and adhesion strength to the glass fiber substrate, as well as satisfactory thermal, mechanical and chemical stabilities. It is another object of the present invention to provide an optical fiber using the same.
• R 1 's are each independently hydrogen or methyl
• p's are each independently an integer in the range of 0 to 3
• q's are each independently an integer of 1 or higher
• R 2 is an aromatic hydrocarbon linking group having 6 to 20 carbon atoms or an aliphatic hydrocarbon linking group having at least 5 carbon atoms.
• a UV-curable coating composition comprising: (a) 40 to 80 % by weight of a photopolymerizable urethane acrylate oligomer; (b) 1 to 40 % by weight of an alkylene oxide-based urethane acrylate monomer of formula (I); (c) 5 to 55 % by weight of a reactive monomer containing at least one acrylate, methacrylate, or vinyl group; and (d) 1 to 10 % by weight of a photoinitiator.
• Fig. 1 shows a schematic illustration of the curing process of a coating composition coated onto a glass fiber core of an optical fiber by UV irradiation.
• a coating composition according to the present invention will now be described more fully with respect to exemplary embodiment of the invention.
• a UV-curable coating composition of the present invention is characterized in comprising an alkylene oxide-based urethane acrylate monomer containing at least one alkylene oxide therein.
• a UV-curable coating composition of the present invention is essentially composed of (a) 40 to 80 % by weight of a photopolymerizable urethane acrylate oligomer; (b) 1 to 40 % by weight of an alkylene oxide-based urethane acrylate monomer of formula (I); (c) 5 to 55 % by weight of a reactive monomer containing at least one acrylate group, methacrylate group, or vinyl group; and (d) 1 to 10 % by weight of a photoinitiator, but may further comprise (e) conventional other additives such as amine-additives, silane-based monomers, stabilizers, photosensitizers, dispersants, and leveling agents.
• the photopolymerizable urethane acrylate oligomer is used in an amount ranging from 40 to 80 % by weight, based on the total weight of the composition.
• the amount is less than 20 % by weight, there might occur a loss during microbending, and when more than 80 % by- weight, the workability becomes poor due to the result of high viscosity.
• the photopolymerizable urethane acrylate oligomer used in the present invention may be synthesized using a composition comprising (i) a polyol copolymer, (ii) a polyisocyanate, (iii) an acrylate alcohol, (iv) a urethane reaction catalyst, and (v) a polymerization inhibitor.
• polyol copolymer (i) Polyol copolymer
• the polyol copolymer (i) has a number average molecular weight of 100 to 10,000, and preferably comprises a repeating unit of -CH 2 CH 2 O- or - CH 2 CH(CH 2 CH 3 )O-.
• polyol examples include polyester polyol, polyether polyol, polycarbonate polyol, polycarprolactone polyol, tetrahydrofuran propyleneoxide ring opening copolymer, ethylene glycol, propylene glycol, 1,4- butanediol, 1,5-pentanediol, 1,6-hexandiol, neopentyl glycol, 1,4-cyclohexane dimethanol, bisphenol-A type of diols, and the like.
• the polyol copolymer is preferably used hi an amount ranging from 10 to 85 % by weight, based on the total weight of the photopolymerizable urethane acrylate oligomer.
• Preferred examples of the polyisocyanate (ii) used in the present invention include 2,4-tolyenediisocyanate, 2,6-tolyenediisocyanate, 1,3-xylenediisocyanate, 1 ,4-xylenediisocyanate, 1 ,5-naphthalenediisocyanate, 1 , 6-hexanediisocyanate, isophoronediisocyanate (IPDI), a mixture thereof and the like.
• the polyisocyanate is preferably used in an amount ranging from 5 to 40 % by weight, based on the total weight of the photopolymerizable urethane acrylate oligomer.
• acrylate alcohol (iii) which comprises at least one (meth)acrylate and hydroxy group
• examples of the acrylate alcohol (iii), which comprises at least one (meth)acrylate and hydroxy group include 2-hydroxyethyl(meth)acrylate, 2- hydroxypropyl(meth)acrylate, 2-hydroxybutyl(meth)acrylate, 2- hydroxyethylacrylate, 2-hydroxypropylacrylate, 2-hydroxy-3- phenyloxypropyl(meth)acrylate, 4-hydroxybutylacrylate, neopentylglycolmono(meth)acrylate, 4-hydroxycyclohexyl(meth)acrylate, 1,6- hexanediolmono(meth)acrylate, pentaerythritolpenta(meth)acrylate, dipentaerythritolpenta(meth)acrylate, a mixture thereof and the like.
• the acrylate alcohol is preferably used in an amount ranging
• Preferred examples of the urethane reaction catalyst (iv), which is used in the urethane reaction include copper naphthenate, cobalt naphthenate, zinc naphthenate, n-butyltinlaurate, dibutyltindilaurate, tristhylamine, 2- methyltriethylenediamide, a mixture thereof and the like.
• the urethane reaction catalyst is preferably used in an amount ranging from 0.01 to 1 % by weight, based on the total weight of the photopolymerizable urethane acrylate oligomer.
• Preferred examples of the polymerization inhibitor (v) include hydroquinone, hydroquinone monomethylether, para-benzoquinone, phenothiazine, a mixture thereof and the like.
• the polymerization inhibitor is preferably used in an amount ranging from 0.01 to 1 % by weight, based on the total weight of the photopolymerizable urethane acrylate oligomer.
• Said photopolymerizable urethane acrylate oligomer (A) may be synthesized using above components as follows:
• a polyisocyanate is added in a round-bottom flask equipped with a stirrer. While stirring at 200 to 300 rpm, a urethane reaction catalyst is added (in an amount of about 1/3 based on the total catalyst) and a polyol copolymer (i) is slowly added thereto. The mixture is allowed to react at about 70 to 8O 0 C for about 2 to 3 hours. Then, the NCO concentration of the reaction product is suitably adjusted to obtain a urethane prepolymer, and a polymerization inhibitor (v) and an acrylate alcohol (iii) are slowly added thereto. The mixture is allowed to react at 80 ° C for 3 hours.
• the reaction is terminated after confirming the disappearance of NCO peak at 2270cm '1 by infrared spectrometer, to obtain a photopolymerizable urethane acrylate oligomer.
• the photopolymerizable urethane acrylate oligomer obtained by above method preferably has a number average molecular weight of 5,000 to 50,000 (determined by gel permeation chromatography (GPC)) and a viscosity of 10,000 to 30,000 cps (determined by Brookfield viscometer HB type, spindle #51, at 40 ° C).
• the alkylene oxide-based urethane acrylate monomer of formula (I) which is used to provide improved hydrophobicity to a coating layer, is obtained by conducting a reaction of (a) a polyisocyanate, (b) an alkylene oxide-containing hydroxy(meth)acrylate of formula (II), (c) a urethane reaction catalyst and (d) a polymerization inhibitor.
• R 2 is an aromatic hydrocarbon linking group having 6 to 20 carbon atoms or an aliphatic hydrocarbon linking group having at least 5 carbon atoms.
• q's are preferably an integer in the range of 1 to 20 and R 2 is an isophrone, 1,6-hexane, or 2,4-tolyene moiety.
• the molar ratio of the polyisocyanate and the alkylene oxide-containing hydroxy(meth)acrylate is preferably in the range of 1 :2 to 1:2.5.
• the urethane reaction catalyst and polymerization inhibitor may be used in an effective amount, preferably in an amount ranging from 10 to 20 parts by weight based on the total weight of the polyisocyanate.
• the alkylene oxide-containing hydroxy(meth)acrylate (b) may be polyalkyleneglycol(meth)acrylate such as polyethyleneglycolmono(meth)acrylate and polypropyleneglycolmono(meth)acrylate, and may be commercially available one selected from the group consisting of Bisomer PEA6, PPA6, PEM6LD, PPM5S, PEM63P, PEM63E (dev) and PEM3(dev) from Cognis Co., EA-051, EA- 101, EM-051, EA-060, EM-06, EMF-063, EAF-071P, EMF-083, EMF-090, EAF- 101P and EAF-201P from Hannong Chemicals Inc.
• PEA6, PPA6, PEM6LD, PPM5S, PEM63P, PEM63E (dev) and PEM3(dev) from Cognis Co.
• Polyisocyanate (a), urethane reaction catalyst (c) and polymerization inhibitor (d) used for preparing an alkylene oxide-based urethane acrylate may be same as those used for preparing a polymerizable urethane acrylate oligomer (a).
• Said alkylene oxide-based urethane acrylate monomer may be synthesized using above components as follows:
• a polyisocyanate (a) is added in a round-bottom flask equipped with a stirrer. While stirring at 200 to 300 rpm, a urethane reaction catalyst (c) is added thereto. The mixture is allowed to react at 40 to 70°C. Then, a polymerization inhibitor (d) and an alkylene oxide-containing hydroxy(meth) acrylate (b) are slowly added thereto. The mixture is allowed to react at about 70 to 90 ° C for about 2 to 3 hours. The reaction is terminated after confirming the disappearance of NCO peak at 2270cm "1 by infrared spectrometer, to obtain an alkylene oxide-based urethane acrylate monomer (B).
• the alkylene oxide-based urethane acrylate monomer obtained by above method preferably has a number average molecular weight of 1,000 to 10,000 (determined by gel permeation chromatography (GPC)), a viscosity of 3,000 to 10,000 cps (determined by Brookfield viscometer HB type, spindle #51, at 25 0 C) and a refractory index of 1.45 or more, more preferably 1.45 to 1.47.
• GPC gel permeation chromatography
• Said alkylene oxide-based urethane acrylate monomer may be preferably used in an amount ranging from 1 to 40 % by weight, and when the amount is less than 1 % by weight, moisture absorption of a coating layer after cure may somewhat increase, and when more than 40 % by weight, cure modulus of a coating layer may increase.
• the reactive monomer (C) used in the present invention preferably has a low number average molecular weight of 100 to 300 in order to balance a working viscosity of the monomer with that of said photopolymerizable urethane acrylate oligomer (A) having a high molecular structure.
• the reactive monomer preferably has at least one acrylate group, methacrylate group or vinyl group.
• the reactive monomer contains various functional groups of 1 to 4, preferably 1 to 3. In particular, a reactive monomer having a high tensile strength and low cure shrinkage is preferred.
• Preferred examples thereof include phenoxyethylacrylate, phenoxyethyleneglycolacrylate, phenoxytetraethyleneglycolacrylate, phenoxyhexaethyleneglycolacrylate, isobonylacrylate (IBOA), isobonylmethacrylate, N-vinylpyrrolidone (N-VP), N- vinylcaprolactam (N-VC), acryloyl morpholine (ACMO), bisphenol ethoxylate diacrylate, ethoxylate phenol monoacrylate, polyethyleneglycol 400 diacrylate, tripropyleneglycol diacrylate, trimethyl propane triacrylate (TMPTA), polyethyleneglycol diacrylate, ethyleneoxide-addition triethylpropantriacrylate, pentaerythritol tetraacrylate (PETA), 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, ethoxylated pentaeryth
• the reactive monomer is preferably used in an amount ranging from 5 to 55 % by weight based on the total weight of a UV-curable coating composition.
• amount is less than 5 % by weight, it may be difficult to lower a viscosity of the oligomeric product to a working viscosity ranging from 3,000 to 10,000 cps (25° C), and when more than 55 % by weight, poor properties such as high viscosity, enlargement of particles, unbalanced surface upon cure, and photo- losses occurs, due to the decreases of the cure shrinkage and thermal stability at high temperature.
• the photoinitiator (D) is used to help a fast cure speed of a resin itself, in order to keep a pace with optical fiber coating speed of l,500m/min.
• the photoinitiator forms free radicals and attacks double bonds in resins to induce polymerization.
• Irgacure #184 hydroxycyclohexylketone
• Irgacure #907 (2-methyl-l[4- (methylthio)phenyl]-2-mo ⁇ holino-propan-l-one)
• Irgacure #500 hydroxy- ketones and benzophenone
• Irgacure #651 (benzildimethyl-ketone)
• Darocure #1173 (2-hydroxy-2-methyl-l-phenyl-propan-l-one
• Darocure TPO 2,4,6- trimethylbenzoyl diphenylphosophinoxide
• Darocure CGI#1800 bisacylphosphineoxide
• CGI#1700 bisacyl phosphine-oxide and hydroxy ketone
• the UV-curable composition of the present invention may comprise conventional other additives such as amine additives, silane-based monomers, stabilizers, photosensitizers, dispersants, and leveling agents, in effective amounts, preferably in amounts ranging from 1 to 5 weight based on the total weight of the UV-curable coating composition.
• Said amine additives are used to prevent a coating composition from polymerization caused by a high temperature and a light before cure, from a hydrogen gas release after cure, and from transmission losses, as well as to provide a fast cure speed.
• Preferred examples thereof include diallylamine, diisopropylamine, diethylamine, diethylhexylamine, triethylamine, N- methyldiethanolamine, ethanolamine and diethanolamine.
• the amine additives are preferably used in an amount ranging from 0.01 to 0.5 % by weight based on the total weight of the UV-curable coating composition.
• the UV-curable coating composition of the present invention may comprise a silane-based monomer or a stabilizer to inhibit the decrease of adhesion strength between the coating layer and glass.
• the silane-based monomer provides improved adhesion strength as well as reduced absorption to a resin composition.
• Representative examples of the silane-based monomer include vinyl trimethoxy silane from Chisso Co.
• silane-based monomer may be used in an amount ranging from 1 to 5 % by weight based on the total weight of a composition.
• stabilizer which acts to improve thermal, oxidative and storage stabilities of a coating composition
• examples of stabilizer include Irganox 1010, Irganox 1035, Irganox 1076 and a mixture thereof from Ciba Co.
• the stabilizer may be preferably used in an amount ranging from 0.1 to 5 % by weight based on the total weight of a composition.
• conventional substances known as photosensitizers, dispersants and leveling agents may be used.
• a method for preparing the UV-curable coating composition of the present invention is as follows: A photopolymerizable urethane acrylate oligomer (a), an alkylene oxide- based urethane acrylated monomer (b), a reactive monomer (c), a photoinitiator (d) and other additives (e) are added to a reactor. The mixture is stirred under a temperature of 15 to 50°C, a humidity of 60% or less and a homogenous speed of l,000rpm or more, by using a dispersion impeller.
• the viscosity of photopolymerizable urethane acrylate oligomer (a) increases, resulting in difficulties of processing, and when the reaction is carried out at more than 50 ° C, the photoinitiator (D) may form radicals, resulting in curing.
• the reaction is carried out at more than 60% of humidity, bubbles may be generated from a resin composition during a subsequent coating process and a side-reaction in which non-reactants reacts with moistures on air may occur. Further, when the mixture is stirred at less than l,000rpm, mixing may be incomplete.
• the coating composition of the present invention is used to prepare a coating layer or film, and the coating layer or firm has the following characteristics: If the composition is used to prepare a 10 to 40 ⁇ m-thick film coated on a glass fiber substrate by curing, the film remains tightly adhered on the glass even after being dipped in 45 to 85 0 C water for a prolonged time (e.g., at least 60 days). In particular, the degree of reduction in the adhesion strength of the film is merely less than 10% even when dipped in 50 ⁇ 70°C water.
• the film has a water absorption ratio of less than 1% in 50 to 70 ° C water and secant a modulus of 0.1 to 0.3 kgf/mm 2 .
• An optical fiber having a 10 to 40 ⁇ m-thick layer can be prepared by coating the UV-curable coating composition of the present invention which has thermal and water resistances, on a glass fiber core, and curing by UV irradiation
• D-bulb having a light intensity of 0.5 ⁇ 3 J/cm 2 and speed of 30 ⁇ 150fpm may be used.
• the optical fiber prepared by above method has improved thermal and water resistances, without causing the photosignal loss or reduction of adhesion strength even when dipped in water at a high temperature for a prolonged time. Accordingly, the optical fiber of the present invention shows improved thermal, mechanical, and chemical stabilities, in particular, no delamination when dipped in 45 ⁇ 85°C water for a prolonged time (e.g., at least 60 days).
• the NCO concentration of the reaction product (theoretically 0.6%) was adjusted to 0.1 to 0.3% to obtain a urethane prepolymer, and 0.05g of hydroquinonemonomethylether (HQMME; Eastman Co.) and 49.6g (0.43 mole) of 2-hydroxyethylacrylate (2-HEA; Nippon shokubai Co.) were slowly added thereto.
• the mixture was allowed to react at 80 ° C for 3 hours.
• the reaction was terminated after confirming the disappearance of NCO peak at 2270cm "1 by infrared spectrometer, to obtain a photopolymerizable urethane acrylate oligomer.
• the oligomer has a number average molecular weight of 22,000g/mol (determined by gel permeation chromatography (GPC)), a viscosity of 15,200cps at 25°C, and an average urethane bonding number of 6.
• the reaction was terminated after confi ⁇ ning the disappearance of NCO peak at 2270cm '1 by infrared spectrometer, to obtain an alkylene oxide-based urethane acrylate monomer.
• the monomer has a number average molecular weight of l,300g/mol (determined by gel permeation chromatography (GPC)), a viscosity of 3,200cps at 25°C, and an average urethane bonding number of 2.
• Preparation Example 3 Preparation of an alkylene oxide-based urethane acrylate monomer (B) - 2 nd option 188g (1.08mol) of 2,4-tolyenediisocyanate (Lyondell chemical Co.) and 0.05g of dibutyltindilaurate were added to a IL round-bottom flask equipped with a stirrer. The mixture was kept below 40 0 C, and 0.05g of hydroquinonemonomethylether and 8 Hg (2.16mol) of PPM5S (PO (5mol) addition 2-hydroxy acrylate; Cognis Co.) were slowly added thereto. The mixture was allowed to react at 8O 0 C for 3 hours.
• PPM5S PO (5mol) addition 2-hydroxy acrylate; Cognis Co.
• the NCO concentration of the reaction product (theoretically 0.8%) was adjusted to 0.4 to 0.6% to obtain a urethane acrylate monomer.
• the reaction was terminated after confirming the disappearance of NCO peak at 2270cm "1 by infrared spectrometer, to obtain an alkylene oxide-based urethane acrylate monomer.
• the monomer has a number average molecular weight of l,200g/mol (determined by gel permeation chromatography (GPC)), a viscosity of 3,800cps at 25°C, and an average urethane bonding number of 2.
• the reaction was terminated after confirming the disappearance of NCO peak at 2270cm "1 by infrared spectrometer, to obtain an alkylene oxide-based urethane acrylate monomer.
• the monomer has a number average molecular weight of l,400g/mol (determined by gel permeation chromatography (GPC)), a viscosity of 3,500cps at 25 ° C, and an average urethane bonding number of 2.
• UV-curable coating compositions were obtained by combining the photopolymerizable urethane acrylate oligomer prepared in Preparation Example 1 and alkylene oxide-based urethane acrylate monomers prepared in Preparation Examples 2 to 4, together with other ingredients, in amounts shown in Table 1.
• Viscosities of the compositions prepared in Examples and Comparative Examples were measured in a torque ranging from 50 to 90% by using a Brookfield DV III+ viscometer, #31 spindle, according to ASTM D-2196.
• compositions prepared in Examples and Comparative Examples were coated on a 20x20 cm glass by using a bar coater having a fixed thickness of 7 to lOmil. After being placed into a fixing frame, the coated film was cured in a nitrogen gas (401pm) under a light with a radiation intensity of 2.5 J/cm 2 and a speed of 30fpm by using 600 W, 9mm of D-bulb (model DRS10/12-QN; Fusion Co.) to obtain a cured lOO ⁇ m-thick film. The cured film was separated from the glass plate and cut into 13mm of width by using a JDC cutter. The cut film was equilibrated in a desiccator of 23°C, RH 50%, for one day. Then, 2.5% secant modulus was measured by pulling the film with a speed of 25mm/min by using 4443 UTM (Intron Co.).
• compositions prepared in Examples and Comparative Examples were coated on a 20x20 cm glass by using a bar coater having a fixed thickness of 5mil. Then, a secondary coating was coated in a thickness of lOmil thereon. After being placed into a fixing frame, the coated film was cured in a nitrogen gas
• the other sample was dipped in 65°C of water for 10 days, kept in a dark place for 6 hours, and a degree of adhesion strength to a glass was measured by pulling the film with a speed of 25mm/min by using 4443 TTM (Intron Co.).
• the adhesion strength was represented by N (Newton) value, and the ratio % was calculated by the following equation, as shown in Table 2.
• Ratio % (Adhesion strength (N) after being dipped in water / Adhesion strength (N) after cure) x 100
• compositions prepared in Examples and Comparative Examples were coated on a 20x20 cm glass by using a bar coater having a fixed thickness of 7 to lOmil. After being placed into a fixing frame, the coated film was cured in a nitrogen gas (401pm) under a light with a radiation intensity of 2.5 J/cm 2 and a speed of 30fpm by using 600 W, 9mm of D-bulb (model DRSl 0/12-QN; Fusion Co.) to obtain a cured film. The cured film was cut into 20mm of width, equilibrated in a desiccator of 23 "C, RH 50% for one day, and then weights (average) of samples were measured (a).
• compositions prepared in Examples and Comparative Examples were coated on a 20x20 cm glass by using a bar coater. After being placed into a fixing frame, the coated film was cured in a nitrogen gas (401pm) under a light with a radiation intensity of 2.5 J/cm 2 and a speed of 30f ⁇ m by using 600 W, 9mm of D-bulb (model DRS10/12-QN; Fusion Co.) to obtain a cured 600 ⁇ m-thick film. The cured film was cut into about 15mm of length and 20mm of width to prepare a sample for measurement. The geometrical values were measured using the prepared sample by DMTA IV (Dynamic mechanical temperature analysis; Rheometry), and the measured geometrical values were input.
• DMTA IV Dynamic mechanical temperature analysis
• the measurement was carried out by cooling the sample to about -100 0 C and warming the sample to about 60 ° C by 2"C/min.
• the test frequency was 1.0 radian/sec.
• the Tg transition glass temperature
• a glass fiber having a diameter of 125 ⁇ m was passed through a die (2 mL) containing a coating composition while UV-curing.
• the UV-cure was carried out by using a D-bulb (Fusion Co.) under a radiation intensity of 1.0 J/cm 2 (UVA region) and a speed of 150fpm.
• the thickness of the coated film was from lO ⁇ m to 30 ⁇ m.
• the cured glass fibers were dipped in 45 ⁇ 65 ° C water. Every day (60 days of period), ten of the fibers were dried at a room temperature for 10 minutes, cut into 10cm of length. Then, interfaces between the glass and coating layer of total 10 fibers were observed by an optical microscope (dimension ⁇ 200), to check a degree of water infiltration.
• the coating films obtained from the compositions of Examples 1 to 9 each exhibited a low degree of reduction in the adhesion strength of less than 10% and a low degree of water absorption of less than 1%, as compared with those of the coating films obtained from the composition of Comparative Examples 1 to 3 having no alkylene oxide-based urethane acrylate monomer. Further, it was confirmed that the degree of adhesion strength reduction and water absorption became even lower when the content of alkylene oxide-based urethane acrylate monomer increased.
• the inventive coating films showed no delamination phenomenon even when dipped in water at a high temperature for a prolonged time, while those of the coating firms obtained from the composition of Comparative Examples 1 to 3 showed delamination between the glass and coating layer.

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