This invention relates to a liquid composition comprising silicone oligomers. The composition can be utilized to removably bind optical glass fibers in a ribbon.

Optical glass fibers can be used to carry signals between devices. Individual optical glass fibers that are to run together for a distance are conventionally removably bound together in a ribbon. The ribbon is produced by applying a coating composition to juxtaposed optical glass fibers.

It is important that each optical glass fiber be properly connected to the device receiving or transmitting the signals or to the end of another optical glass fiber. To achieve a proper connection, both ends of each optical glass fiber in the ribbon must be located. Optical glass fibers are conventionally located by color coding each optical glass fiber with a different color. Individual optical glass fibers are partially broken out of the ribbon to permit connections to be made. Ribbon coatings are unsatisfactory if they do not have the requisite low tear strength to permit individual optical glass fibers to be partially broken out of the ribbon without destroying the ribbon coating surrounding other optical glass fibers in the ribbon.

Ribbon coatings are also unsatisfactory if they adhere too strongly to the optical glass fiber thereby removing some or all of the color coding when the optical glass fiber is broken out which can lead to confusion and improper connections.

Ribbon coatings are also unsatisfactory if they do not have a sufficiently high modulus to withstand the physical forces that occur during the manufacture and use of the ribbon.

An optical glass fiber experiences different attenuations at different temperatures. Attenuation is a reduction in strength of the signal carried by the optical glass fiber and is due to stresses developed in the optical glass fiber caused by the temperature change. An attenuation as low as possible is preferred and further a constant attenuation over a wide range of temperatures is preferred. Many ribbon coating compositions do not help maintain a constant attenuation, but instead increase the attenuation.

The liquid compositions of the present invention include unique silicone oligomers and can be utilized as ribbon coating compositions for releasably binding juxtaposed optical glass fibers in a ribbon. These liquid compositions overcome the shortcomings of the prior art ribbon coating compositions.

This invention is directed to a liquid composition comprising (1) a silicone oligomer comprising a group derivable from an alkoxylated silicone, at least two groups chosen from the group consisting of urethane and urea groups obtained from a polyisocyanate, and at least one ethylenical unsaturation and (2) at least one polyfunctional cross-linking agent. The invention further relates to a liquid composition comprising (1) a silicone oligomer obtainable by reacting an alkoxylated silicone comprising at least one functional group chosen from the group consisting of hydroxy groups and amine groups, at least one polyisocyanate and at least one hydroxy functional ethylenically unsaturated monomer and (2) at least one polyfunctional cross-linking agent.

The mole ratio of silicone: polyisocyanate:ethylenically unsaturated monomer utilized to produce the silicone oligomer is preferably about 1:1.5:1.5 to about 1:4:4.

In US-A-4.136.250 a silicone oligomer is described that is derivable from a hydroxyterminated silicone and a hydroxy terminated acrylate reacted with a diisocyanate.

US-A-4.136.250 however does not describe the use of a polyfunctional cross-linking agent and therefore does not produce the preferential liquid composition of the invention. US-A-4.136.250 is directed to hydrogels and not to a composition that can be used as a binder for optical glass fibers in a ribbon. US-A-4.136.250 is hereby incorporated by reference with respect to the description of the silicone oligomer.

The liquid composition can be applied to coat an optical glass fiber. The term optical glass fiber refers to a fiber made of glass and used in an optical application, but a fiber of any other material can be coated with a liquid composition according to the invention and be applied in any other field. Preferably the liquid composition is applied to optical glass fibers.

The liquid composition can be utilized to produce a ribbon coating that releasably binds juxtaposed optical glass fibers in a ribbon.

The cured ribbon coatings of the present invention have a low tear strength that permits an optical glass fiber to be easily broken out from the ribbon without adversely affecting the remainder of the ribbon. The cured ribbon coatings of the present invention have an adherence to the optical glass fiber that is strong enough to produce a ribbon but not strong enough to remove the color coding from the optical glass fiber coating when the fiber is broken out of the ribbon. Thus, the ribbon coatings of the present invention exhibit good break-out properties.

The cured ribbon coatings have a high modulus that permits the ribbon to withstand the physical forces exerted thereon during the manufacture and use of the ribbon. The physical properties of the ribbon coating are relatively stable over a temperature range to which the ribbon is conventionally exposed, i.e., about -40° to 85°C. It is presently believed that this stability helps maintain a relatively constant attenuation of the strength of the

signal carried by the optical glass fiber because the ribbon coating does not stress load the optical glass fiber due to thermomechanical changes to the same extent that conventional materials impart a stress load.

The alkoxylated silicone preferably has functional groups, e.g., hydroxy groups, amine groups, the like, and mixtures thereof that are reactive with the isocyanate group of the polyisocyanate.

A silicone has a structure that includes at least one silicon-oxygen (Si-O) group.

The alkoxylated silicone is preferably hydroxy and/or amine functional and has about 2 to about 4, preferably about 2 to about 3, functional groups per molecule of alkoxylated silicone.

The alkoxy group of the alkoxylated silicone preferably contains about 1 to about 6, more preferably about 1 to about 4, carbon atoms per alkoxy group. Representative of the alkoxy groups are methoxy, propoxy, and the like. More than one alkoxy group can be present on a silicon atom. The silicon can further be alkyl substituted.

The alkoxylated silicone preferably contains up to about 75, more preferably about 15 to about 60, weight percent silicone and alkyl substituted silicone groups per alkoxylated silicone molecule. The weight percent is based on the total weight of the alkoxylated silicone molecule.

The alkoxylated silicone preferably contains at least about 25, more preferably about 40 to about 85, weight percent alkoxy groups per alkoxylated silicone molecule.

The number average molecular weight of the alkoxylated silicone is preferably about 250 to about 15,000, more preferably about 1,500 to about 3,500, daltons.

The term "dalton", as used in its various grammatical forms, defines a unit of mass that is one-twelfth the mass of carbon-12.

Representative of the alkoxylated silicones is the triol DC 193 and the diol Q4-3667 both commercially available from Dow Corning.

These silicons have a structure according to

roup and in can each independently be chosen such that the molecular weight falls within the preferred ranges. The functional groups can have . the formula -(CH,) -R 5, in which R5 is chosen from amine and hydroxy groups, and in which Z is 0 to 10.

The polyisocyanate is preferably a diisocyanate although higher functionality polyisocyanates can be utilized. Representative diisocyanates include isophorone diisocyanate (IPDI), toluene diisocyanate (TDI), diphenylmethylene diisocyanate, hexamethylene diisocyanate, cyclohexylene diisocyanate, methylene dicyclohexane diisocyanate, 2,2,4-trimethyl hexamethylene diisocyanate, m-phenylene diisocyanate, 4-chloro-l,3-phenylene diisocyanate, 4,4'-biphenylene diisocyanate, 1,5-naphthalene diisocyanate, 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, 1,10-decamethylene diisocyanate, 1,4-cyclohexylene diisocyanate, and polyalkyloxide and polyester glycol diisocyanates such as polytetramethylene ether glycol terminated with TDI and polyethylene adipate terminated with TDI, respectively.

The hydroxy functional ethylenically unsaturated monomer can be a monoethylenically unsaturated monomer or a polyethylenically unsaturated monomer or a mixture of mono- and polyethylenically unsaturated monomers with monoethylenically unsaturated monomers being preferred. The amount of polyethylenically unsaturated monomer, if present, is selected so as not to cause gelling. The ethylenically unsaturated monomers are preferably monohydroxy functional ethylenically unsaturated monomers.

Representative ethylenically unsaturated monomers include hydroxyalkyl acrylates, hydroxyalkyl methacrylateε.

hydroxyalkyl vinyl ethers, hydroxyalkyl unsaturated dicarboxylates, hydroxy functional carboxylic functional unsaturated monomers, and the like. Mixtures can also be utilized. The alkyl group of the above monomers can be 1 to about 8 carbon atoms in length.

Preferred representative ethylenically unsaturated monomers include hydroxyalkyl acrylates, hydroxyalkyl methacrylates, and mixtures thereof.

Illustrative of the hydroxyalkyl acrylates and methacrylates are hydroxyethyl acrylate, hydroxybutyl acrylate, hydroxypentyl acrylate, the corresponding methacrylates and the like. Illustrative of the hydroxyalkyl vinyl ethers are hydroxymethyl vinyl ether, hydroxybutyl vinyl ether, and the like.

Illustrative of the hydroxyalkyl dicarboxylates are hydroxy propyl monobutyl maleate, hydroxy propyl monoethyl maleate, and the like. The corresponding fumarates, itaconates and the like are also suitable.

Illustrative of the hydroxy functional carboxylic functional unsaturated monomers are maleic acid half esters, and the like, that can be conventionally produced by esterifying one carboxylic group of an unsaturated dicarboxylic acid or anhydride with a diol.

The reaction of the alkoxylated silicone, the polyisocyanate and the hydroxy functional ethylenically unsaturated monomer preferably consumes all of the hydroxy groups, amine groups and isocyanate groups so that no unreacted hydroxy groups, amine groups or isocyanate groups are present.

The mole ratio of alkoxylated silicone: polyisocyanate:ethylenically unsaturated monomer is preferably about 1:1.5:1.5 to about 1:4:4, more preferably about 1:2:2 to about 1:3:3.

The alkoxylated silicone, polyisocyanate and ethylenically unsaturated monomer are conventionally reacted

Preferably the reaction takes place at a temperature of between 30 to 100°C and more preferably at a temperature of between 50 to 80°C. The reaction of an isocyanate group with a hydroxy group produces a urethane group. The reaction of an isocyanate group with an amine group produces a urea group. The presence of urea groups in the silicone oligomer increases the modulus and tear strength of the ribbon coating. Thus, the modulus and tear strength of the ribbon coating can be adjusted by adjusting the amount of urea groups present in the silicone oligomer.

The silicon can e.g. be first reacted with the polyisocyanate and then the product can be reacted with the monomer, or the monomer can be reacted with the polyisocyanate and then the product can be reacted with the silicone, or the three reactants can be reacted simultaneously.

The cross-linking agent has a functionality of about 2 to about 6, preferably about 2 to about 4.

The cross-linking agent can be represented by a polyfunctional (meth)acrylate. Further the composition can comprise monofunctional monomers, such as N-vinyl, styrene, and acrylonitrile monomers, oligomers and polymers of these monomers, similar unsaturated monomers, oligomers and polymers and mixtures thereof. Preferably, the cross-linking agent is a polyfunctional(meth)acrylate. Preferably, the composition does not, or only to a small percentage such as 5 or 10%, contain monofunctional monomers.

The term "(meth)acrylate", and various grammatical forms thereof, identifies esters that are the reaction product of acrylic or methacrylic acid and a hydroxyl-containing compound such as an alcohol. Representative of the preferred cross-linking agents are the following monomers: di(meth)acrylates, e.g., 1,6-hexane diol dimethacrylate and diglycidyl ether Bisphenol-A diacrylate; tri(meth)acrylates, e.g., trimethylol propane triacrylate; tetra(meth)acrylates, e.g..

pentaerythritol tetraacrylate. Two preferred commercially available cross-linking agents are Sartomer C 9003, a diacrylate of neopentyl glycol polypropoxylated with an average of two propylene oxide units per molecule, from Sartomer, estchester, PA and Cargill 1570, a diacrylate ester of Bisphenol-A epichlorohydrin epoxide, from Cargill, Carpentersville, IL. The weight ratio of silicone oligomer to cross-linking agent is preferably about 5:95 to about 95:5, more preferably about 35:65 to about 65:35.

The liquid composition can further comprise an initiator such as a phonoinitiator or an other initiator. Preferably the liquid composition comprises a conventional photoinitiator. Representative of these photoinitiators are 1-hydroxycyclohexyl phenyl ketone which is commercially available from Ciba-Geigy Corp., Ardsley, NY under the trade designation irgacure 184 and 2-hydroxypropyl phenone which is commercially available from EM Chemicals, Hawthorne, NY, under the trade designation Darocur 1173. The photoinitiator is present in the liquid composition in an amount up to about 4 weight percent based on the total weight of the liquid composition. Representatives of other initiators are peroxide initiators such as benzoyl peroxide and azo compounds such as azobisisobutyralnitrile.

Ribbons can be produced by applying the liquid composition to juxtaposed optical glass fibers. The methods of producing these ribbons are conventional. Various forms of actinic energy can be utilized to cure the liquid composition. Representative of these actinic energy sources are mercury lamps, lasers and the like.

The wavelength of the actinic energy suitable for use herein is in or near the ultraviolet range, e.g., actinic energy having a wavelength of about 200 to about 550, preferably about 250 to about 450, nanometers (nm). The term "near" as used in the phrase "near the ultraviolet

range", refers to light at the lower end of the visible light spectrum. The following examples are presented by way of illustration of preferred embodiments of the present invention and not by way of limitation.

EXAMPLE 1 PREPARATION OF A LIQUID COMPOSITION

A liquid composition of the present invention was prepared in a 500 ml, 3 neck flask that was equipped with a variable speed stirrer, an addition funnel, a heating mantel and a dry air sparge. The flask was charged with 43.29 g (0.195 moles) of isophorone diisocyanate and the addition funnel was charged with 27.62 g (0.195 moles) of 2-hydroxy- ethyl acrylate. The hydroxyethyl acrylate was slowly added to the flask over a time period of 30 minutes. The contents of the flask were maintained at a temperature in the range of about 25° to about 30°C during the addition of the hydroxyethyl acrylate. After the entire amount of the hydroxyethyl acrylate had been added to the flask the contents of the flask were maintained for about 30 min within the above temperature range to ensure a complete reaction of the hydroxyethyl acrylate. Next, 234.09 g

(0.097 moles) of alkoxylated silicone triol, i.e., the Dow Corning product DC 193, was introduced into the addition funnel and then slowly introduced into the flask at a rate that did not cause a sudden temperature increase. After all of the DC 193 was introduced into the flask the temperature of the contents of the flask was elevated to about 60°C. This elevated temperature was maintained for a time period sufficient to achieve a residual isocyanate content of less than about 0.1 percent. The reaction product was the silicone oligomer.

This silicone oligomer was admixed with the cross-linking agent trimethyol propane triacrylate and the photoinitiator Darocur 1173 from EM Chemicals in a weight ratio of silicone oligomer:cross-linking

agent:photoinitiator of about 60:37:3 to produce a liquid composition of the present invention. The liquid composition was drawn down as a film and cured using a "D" lamp from Fusion Curing Systems,

Rockville, MD. The "D" lamp emits actinic energy having a wavelength of about 200 to about 407 nm with the peak actinic energy being about 380 nm and a power output of about 300 watts per linear inch. The film was completely

2 cured at a dose of less than 1 J/cm and was hard, water resistant and exhibited the desired poor tear strength.

EXAMPLE 2 POLYMERIZABLE LIQUID COMPOSITION

A silicone oligomer was prepared utilizing a flask as described in EXAMPLE 1 that was charged with 58.53 g (0.264 moles) of isophorone diisocyanate. The addition flask was charged with 30.57 g (0.264 moles) of 2-hydroxyethyl acrylate that was introduced into the flask at a rate such that the temperature of the contents of the flask did not exceed about 30°C. When addition of the hydroxyethyl acrylate was complete, the temperature was maintained for 30 minutes to ensure complete reaction of the hydroxyethyl acrylate. The addition funnel was then charged with 20.9 g (0.0879 moles) of DC 193 which was slowly introduced into the flask at a rate such that the temperature of the contents of the flask did not increase suddenly and did not exceed about 40°C. When the introduction of the DC 193 was complete the temperature of the contents of the flask was elevated to about 60°C and maintained at that temperature for a time period sufficient to obtain a residual isocyanate content of less than about 0.1 percent. A liquid composition was prepared by admixing the above silicone oligomer with the cross-linking agents Cargill 1570 and trimethylol propane triacrylate and the photoinitiator Darocur 1173 in a weight ratio of silicone

oligomer:Cargill 1570:trimethylol propane triacrylate:Darocur 1173 of about 57:10:30:3. A film of this liquid coating composition was cured

2 using the "D" lamp at a dosage of about 0.5 J/cm .

The cured film had a modulus of about 350 MPa.

An amount of the liquid composition was applied as a cabling material to a set of color coded optical fibers.

2 After curing at a cure speed of 0,5 J/cm (dose of UV light) using a 120 Watt/cm medium pressure. Hg lamp the material appeared to provide good breakout properties.