WO1991003498A1

WO1991003498A1 - Polymerizable oligomers and coatings based on butadiene

Info

Publication number: WO1991003498A1
Application number: PCT/US1990/005013
Authority: WO
Inventors: John T. Vandeberg; Kevin P. Murray; John J. Krajewski; John M. Zimmerman
Original assignee: Desoto, Inc.
Priority date: 1989-09-08
Filing date: 1990-09-05
Publication date: 1991-03-21
Also published as: AU6437590A; CA2024730A1

Abstract

A polymerizable ethylenically unsaturated oligomer which is a reaction product of: (1) a polybutadiene oligomer carrying two reactive groups and lacking significant unsaturation, the oligomer containing at least about 60 % by weight of butadiene polymerized inthe 1,2 position with the balance of the butadiene polymerized in the 1,4 position, said difunctional oligomer having a number average molecular weight of from about 500 to about 5,000 daltons and (2) a monofunctional ethylenically unsaturated compound, the unsaturated oligomer having a number average molecular weight of from about 1,000 to about 10,000 and containing at least about 40 % by weight of the polybutadiene oligomer. These unsaturated oligomers are combined with an ethylenically unsaturated liquid comprising alkyl (meth)acrylate to form cured coatings having superior resistance to water.

Description

"POLYMERIZABLE OLIGOMERS AND COATINGS BASED ON BUTADIENE"

DESCRIPTION Technical Field

This invention relates to photopolymerizable ethylenically unsaturated oligomers based on saturated butadiene oligomers having a pair of reactive groups, preferably diols having a high 1,2-butylene content. While unsaturated oligomers of various type are contemplated, unsaturated polyurethanes, which can contain urea groups, are preferred, especially for application to optical glass fibers. The unsaturation which is contemplated is preferably ( eth)acrylate unsaturation or an admixture of vinyl ether groups and enthylenically unsaturated dicarboxylates, preferably maleates or fu arates. The unsaturated oligomers can be cured by exposure to energy, e.g., light, in the presence of a photoinitiator or electrons from an electron beam in the absence of a photoinitiator. Background Art

Ethylenically unsaturated polyurethane oligomers are known to be employed in photocurable compositions which are to be used in the coating of optical glass fibers. One of the problems encountered in the use of the known compositions is the moisture sensitivity of the cured coatings which leads to various difficulties including loss of adhesion upon exposure to moisture. Other difficulties are inadequate thermal stability and inadeguate hydrolytic stability. It is desirable to reduce the moisture sensitivity of the cured coatings while maintaining resistance to embrittlement at low service temperatures, but this is very difficult with the polyether-based polyurethanes and the ether containing unsaturated diluents now in use. Similarly, the polyether-based polyurethanes and the ether-containing diluents provide coatings which lack thermal stability and hydrolytic stability, and it is also desirable to improve these characteristics.

U.S. Pat. No. 4,572,610, discloses the use of polybutadiene oligomer diols to provide photocurable polyurethane coatings for optical glass fibers. Those oligomers were halogenated to consume the residual unsaturation present in the polybutadiene polymer. Hydrogenation rather than halogenation has also been employed to remove residual unsaturation. Unfortunately, the hydrogenated high 1,4-polybutadiene- based products were crystalline, waxy and poorly soluble in the other necessary liquid components of a liquid photocurable composition. While the halogenated products were not as crystalline and waxy as the hydrogenated products, they still possessed the same disadvantages and were particularly poor from the standpoint of thermal stability. Summary of Invention

In accordance with this invention, a polymerizable liquid coating composition comprises an ethylenically unsaturated oligomeric reaction product of components comprising:

(1) a saturated polybutadiene oligomer carrying a pair of reactive groups, preferably a diol, which lacks significant unsaturation and which contains at least about 60%, preferably from 75% to 90% by weight, of butadiene polymerized in the 1,2-position with the balance of the butadiene polymerized in the 1,4-position, this difunctional oligomer being hydrogenated to remove much of the residual unsaturation therefrom, and having a number average molecular weight of from about 500 to about 5,000 daltons;

(2) a molar excess of an organic compound having a plurality of groups reactive with the reactive groups of the oligomer, e.g., the hydroxy groups of the oligomer diol, to provide reactive terminal groups; and

(3) a monofunctional ethylenically unsaturated compound, preferably a (meth)acrylate which is reactive directly with the reactive groups of the polybutadiene oligomer or with the reactive terminal groups of (2) . In place of the (meth)acrylate one can use other monofunctional ethylenically unsaturated compounds, or mixtures thereof, such as a monofunctional vinyl ether or a monofunctional ethylenically unsaturated carboxylate, preferably a maleate or fumarate. since the oligomer is preferably a diol, the monofunctionality of the unsaturated compound is preferably constituted by a single hydroxy group.

The ethylenically unsaturated oligomer which is produced has a number average molecular weight of from about 1,000 to about 10,000, preferably about 1,500 to about 5,000, daltons, and it contains at least about 40% by weight of the polybutadiene oligomer.

It is desired to stress that component (2) above is optional where the monofunctionality of component (3) is directly reactive with the two reactive groups in the oligomer, as by esterification. On the other hand, it is preferred to employ oligomer diols and to react those diols with anhydrides, such as diisocyanates or diepoxides, so as to ease the burden of reaction and thus obtain a substantially complete reaction while avoiding undesired side reactions.

The unsaturation in the polybutadiene oligomer, i.e., (1), must be consumed to an extent that the residual unsaturation no longer disturbs the stability of the photocured composition. This requires the unsaturation to be consumed to an iodine number of less than about 80, preferably less than about 30. The invention includes the unsaturated oligomers, photopolymerizable coatings containing the same, and optical glass fiber coated with these coatings, especially when the coatings are used as primary coatings.

There are many ways that the polybutadiene oligomer can be converted to an ethylenically unsaturated derivative in accordance with this invention. It is preferred that the. described difunctional polybutadiene oligomer, which is preferably a diol, be reacted with a molar excess of an organic compound having a plurality of groups which are reactive with the two reactive terminal groups on the polybutadiene oligomer (which are preferably hydroxy groups) to provide different terminal reactive groups which can be used to introduce the desired ethylenically unsaturated groups. This organic compound is sometimes referred to herein as a polyfunctional component.

The several functional groups of the polyfunctional component are preferably all the same. In such case, the terminal groups provided by the polyfunctional component have the same functionality as the group which reacted with the reactive groups of the oligomer, e.g., its hydroxy-groups. These terminal groups are reacted with a monofunctional (meth)acrylate or a monofunctional vinyl ether and a monofunctional maleate or fumarate, which is usually hydroxy functional. These monofunctional unsaturated compounds are themselves well known and will be more fully discussed hereinafter and further illustrated in the Examples. As will be evident, the two described reactions can be carried out simultaneously or sequentially and both of these variations are. intended to be embraced by reference to a reaction product involving the various reactants.

The polybutadiene oligomer diols which are used herein are made by anionic polymerization and are available in commerce. A preferred commercial product useful herein can be obtained from Nippon Soda Corporation, Ltd. of Tokyo, Japan, under the trade designation Nisso PB GI 1000. This product is a hydrogen-saturated polybutadiene diol having about 85% branched butylene groups formed by a 1,2-polymerization and 15% butylene groups formed by a 1,4-polymerization and a number average molecular weight of about 1,000 daltons. Corresponding products having a number average molecular weight of about 2,000 and 3,000 daltons are also available.

As will be understood, while the preferred difunctional polybutadiene oligomers are hydroxy functional, the hydroxy groups can be replaced by other reactive groups, such as carboxyl groups, mercapto groups, amino groups, and the like. These other reactive groups can be employed in place of the hydroxy group to form ethyenically unsaturated derivatives in much the same way as the oligomer diol. Thus, the diol can be reacted with a diisocyanate and hydroxyethyl acrylate. The oligomer dimercaptan can replace the oligomer diol. Similarly, the oligomer diol can be reacted with acrylic acid to form the unsaturated derivative by ester formation. One can reverse this by esterifying the oligomer dicarboxylate with hydroxyethyl acrylate.

The unsaturated oligomers which have been described can be incorporated into photocurable and electron beam curable coatings because they are not waxy and are satisfactorily soluble in the other components of the coating which are liquid and which function to thin the composition to coating viscosity. Compatibility with long chain monoethylenically unsaturated esters, and particularly with long chain acrylates, is of particular importance in providing cured coatings which are insensitive to water. This is of importance to the provision of primary coatings where the prior art frequently needed ether-containing monomers to provide the required softness and low viscosity, albeit it is also helpful in the formulation of single and secondary coatings.

While polyurethanes are especially useful in the formation of primary coatings and polyepoxide-based materials are especially useful in the formation of secondary coatings, as will be discussed, many oligomer combinations are useful in this invention and are illustrated hereinafter. Detailed Description of the Invention

The difunctional polybutadiene oligomers in this invention should constitute a large proportion of the total weight of the unsaturated oligomer derivatives thereof which are used herein, more particularly at least about 40% and more preferably at least about 45%.

In general, lower modulus coatings will contain a higher proportion of the polybutadiene oligomer in the unsaturated oligomer derivative, and vice versa, so a preferred unsaturated oligomer used in a secondary coating for optical glass fiber will contain from 45% to 55% by weight thereof. In a primary coating the polybutadiene oligomer will constitute at least 50% by weight of the unsaturated oligomer made therefrom, preferably at least 70% by weight. The difunctional polybutadiene oligomers of the present invention are also useful to prepare cable structures including ribbon materials wherein coated fibers are bound together with a cured coating composition of the present invention.

All proportions and percentages herein are by weight, unless otherwise stated, and molecular weights, as is conventional, are reported in daltons.

The term "dalton", as used herein in its various grammatical forms, defines a unit of mass that iε l/12th the mass of carbon-12.

The compositions of the present invention are curable by exposure to ultraviolet light when a photoinitiator, including visible light near the ultraviolet range. ^' Appropriate wavelengths will be discussed hereinafter.

Photoinitiators include aryl ketones and are sometimes added to the composition shortly before use. When the monoethylenically unsaturated compound comprises a vinyl ether and a maleate or fumarate, the preferred photoinitiator is selected from the group consisting of hydroxy or alkoxy-functional acetophenone derivatives and benzoyl diaryl phosphine oxides.

The present compositions are also curable by exposure to electrons from an electron beam in the absence of a photoinitiator.

The polybutadiene oligomer can be an acrylate- ter inated polyurethane containing the polybutadiene diol. This polyurethane can be made by reacting polybutadiene diol with an organic diisocyanate and a monohydric acrylate, in any order.

The organic diisocyanates are well known and are illustrated by toluene diisocyanate and isophorone diisocyanate which are two of the more frequently used compounds within this well known class. The urethane forming reaction is well known and is generally carried out at moderate temperatures of from about 40^* to about 80^* C in the presence of a small amount of a catalyst for the urethane forming reaction, typically 0.1-0.2% of dibutyl tin dilaurate. Other appropriate urethane forming catalysts are illustrated by amines, such as tributyl amine or triethylene diamine.

The molar excess of diisocyanate over diol is proportioned in known fashion to form an isocyanate- terminated polyurethane which is then acrylate- terminated with monohydric acrylate to provide an acrylate- terminated polyurethane having a number average molecular weight of from about 1,000 to about 10,000, preferably from 1,500 to 5,000 daltons. When polyfunctional materials other than diisocyanates are used, the polybutadiene oligomer should have the above range of molecular weights.

The acrylate terminal group in the polyurethane is introduced with a urethane linkage by the reaction of the isocyanate group with a hydroxy group supplied by a monohydric acrylate, typically 2- hydroxyethyl acrylate. 2-hydroxypropyl acrylate and 2- hydroxybutyl acrylate are also useful. Monohydric polyacrylates, such as glyceryl diacrylate, are also useful.

The ethylenically unsaturated dicarboxylate can be produced by conventional esterification of at least one of the carboyxl groups of the dicarboxylic acid. Representative dicarboxylic acids include maleic acid, fu aric acid, itaconic acid, and the like.

Maleates and fumurates are preferred and are discussed herein in further detail, it being understood that other dicarboxylates can be utilized.

The maleate or fumarate group can be introduced instead of the acrylate terminated group using hydroxy functional esters of maleic or fumaric acid, such as hydroxypropyl butyl maleate or fumarate.

As will be evident, the hydroxy groups in the above described illustration of this invention can be replaced by any group that is reactive with the functional group of the polyfunctional compound or the reactive groups of the polybutadiene oligomer.

When a polyepoxide, such as a diepoxide, is used as the organic compound and reacted with the diol, the reaction product is an alpha-hydroxy ether instead of a urethane. This reaction can be carried out in the presence of a Lewis acid catalyst by heating to reaction temperature which is conveniently in the range of 100 to 120^* C. After removal or neutralization of the Lewis acid, the terminal epoxy-groups provided by the molar excess of polyepoxide are then reacted with a monofunctional unsaturated compound, typically acrylic acid or methacrylic acid. The reaction with these acids is a simple esterification reaction which can also be carried out without catalyst, albeit a trace of a tertiary amine or a quaternary ammonium salt will facilitate the esterification. One can also rely upon the acidity remaining from the first stage of the reaction. The reactions of the epoxy group with hydroxy and carboxyl functionality are themselves well known, as illustrated hereinafter.

Diepoxides based on bisphenol A, such as the diglycidyl ether of bisphenol A supplied by Shell Chemical Company under the trade designation Epon 828 which has a number average molecular weight of about 390 daltons, are particularly preferred because they form hard and water-resistant reaction products having good heat resistance. When a polycarboxylic acid is used as the organic compound and reacted with the oligomer diol, the reaction can be carried out in several ways. Thus, the anhydride can be adducted onto either the oligomer diol or the monofunctional unsaturated compound to provide a terminal carboxyl group which is later reacted with the other hydroxy-functional component. While polycarboxylic acids, such as phthalic acid, trimellitic acid, maleic acid, or fumaric acid, can be used, it is more convenient to employ the polycarboxylic acid in the form of an anhydride, especially a dicarboxylic acid anhydride. Again, the polycarboxylic acid is used in a molar excess with respect to the oligomer diol which is selected to control the molecular weight. In some instances it will be understood that the polybutadiene oligomer has sufficient molecular weight that additional chain extension is unneeded. In such instance the polyfunctional component is used in a molar excess of 2:1 with respect to the oligomer. When chain extension is desired, the molar excess will be less than 2:1, as is well known.

Referring more particularly to the liquid coating compositions which are contemplated, these will contain one or more liquid ethylenically unsaturated materials which will copolymerize with the unsaturation on the ethylenically unsaturated oligomer, which is based on the polybutadiene oligomer, upon exposure to light. These liquids, which are reactive through their ethylenic unsaturation, are used to reduce the viscosity to facilitate coating application, and the added liquid can be monoethylenically or polyethylenically unsaturated. Thus, the balance of the composition comprises one or more ethylenically unsaturated liquids unless a cationic cure is intended. The ethylenically unsaturated liquids which are used herein preferably include a long chain alkyl (meth)acrylate, preferably one having at least carbon atoms in the alkyl group. These long chain alkyl groups normally do not exceed about 20 carbon atoms. Long chain acrylates are poorly compatible with the polyether polyurethanes utilized in the prior art, but they are excellently compatible with the unsaturated oligomers provided herein. As a result of the enhanced capacity to tolerate long chain acrylates, photopolymerizable coatings possessing superior insensitivity to water as a result of both the selection of the unsaturated oligomer and the selection of the unsaturated monomer used to provide coating viscosity are provided by this invention. This is of particular importance in primary coatings where the usual monomers employed to soften and flexibilize the oligomers are polyethers. This is why the primary coatings now in use possess inadequate water and/or thermal resistance.

The term "liquid", and any other term used herein to describe the physical condition of anything, is used in its normal sense to denote the condition at room temperature (20^* to about 30^* C) . It is known that primary coatings for optical glass fibers must have great softness (low modulus and low glass transition temperature) in order to adequately resist low temperature microbending. On this basis the modulus of the cured coating should be below about 3.0 Megapascals and its glass transition temperature (T_g) should be below about 20^* C. Industry now prefers the modulus to be in the range of from 1.0 to 1.5 megapascals with a (T ) below about -12^* C, and this difficult standard can be satisfied by this invention. The glass transition temperature is the temperature at which a homopolymer of the monomer changes from a solid to a vitreous state.

Industry has demanded better water and thermal resistance, but have had little effective choice because manufacturers must accept the limitations of the available materials. Thus, while accepting products that have inadequate water and thermal resistance, industry has continued to urge its suppliers to provide primary coatings of preferred low modulus which have superior water and thermal resistance.

When the needed low viscosity is supplied using the usual ether-containing monoacrylates having a below -20 degrees C, which enables one to provide the low modulus needed for a primary coating, the water resistance is poor. The usual ether-containing low glass transition temperature monomers are illustrated by ethoxyethoxyethyl acrylate, phenoxyethyl acrylate, butoxyethyl acrylate, 2-hydroxyethyl acrylate, and mixtures thereof. It has recently been discovered that nonyl-substituted phenoxyethyl acrylate, and the like provide better water and thermal resistance. Nonetheless, all of these ethers and polyethers introduce at least some limited water sensitivity. In this invention we preferably replace the above ethers in whole or in part by long chain acrylates and methacrylates, preferably acrylates illustrated by isooctyl acrylate, dodecyl acrylate, isodecyl acrylate, and commercial mixtures of octyl and decyl acrylates. The preferred alkyl (meth)acrylates contain at least 6, preferably 8 to 12, carbon atoms in the alkyl group. With this replacement we can provide low modulus primary coatings having superior water resistance.

When vinyl ether groups are used to terminate the oligomer, as can be achieved using butylene glycol monovinyl ether, then the polymaleates or polyfumarates used to help cure that oligomer should contain hydrocarbon groups having at least 6 carbon atoms. The use of the vinyl ether group in combination with a maleate or fumarate results in increased cure speed which is desirable.

While useful results are obtained without a precise balance between the vinyl ether groups and the maleate or fumarate groups, the fastest and best cures are obtained when these two groups are present in about stoichiometric proportions, i.e., about 1:1. Thus, the cure speed falls off badly when the equivalent ratio of the two types of groups is outside the range of about 5:1 to about 1:5, preferably 2:1 to 1:2. These two separate functionalities may be present in the same oligomeric molecule, i.e., the vinyl ether compound and the ester can be present in the same oligomeric molecule.

To illustrate an oligomeric molecule having the two types of unsaturations one may provide the vinyl ether group in a compound such as hydroxybutyl vinyl ether. Maleic anhydride can be adducted with butyl alcohol to form monobutyl maleate which is then adducted with a molar proportion of propylene oxide to form 2-hydroxypropyl monobutyl maleate. One mole of hydroxybutyl vinyl ether and one mole of 2-hydroxypropyl monobutyl maleate can then be reacted with one mole of a conventional organic diisocyanate, like isophorone diisocyanate. This reaction is preferably carried out in two stages so that all of one of the two unsaturated compounds bonds with the more reactive isocyanate group on the diisocyanate, and then the second unsaturated compound is added to react with the remaining isocyanate group. The result is a polyurethane formed in conventional manner using catalysts such as dibutyl tin dilaurate and temperatures of bout 30^*C. in the first stage and 60^*C. in the second stage. This polyurethane contains vinyl ether groups and maleate groups in the same molecule, and these can be cured by appropriate light, or other forms of energy, exposure in accordance with this invention.

Preferred photoinitiators when a vinyl ether group is utilized in combination with a maleate or fumarate are hydroxy or alkoxy-functional acetophenone derivatives, preferably hydroxyalkyl phenones, or benzoyl diaryl phosphine oxides.

The acetophenone derivatives which may be used have the formula:

in which is an optional hydrocarbon substituent containing from 1 to 10 carbon atoms and which may be alkyl or aryl, e.g., methyl, ethyl, butyl, octyl or phenyl, X is selected from the group consisting of hydroxy, C, to C₄ alkoxy, C₁ to C₈ alkyl, cycloalkyl, halogen, and phenyl, or 2 Xs together are cycloalkyl, and at least one X is selected from the group consisting of hydroxy and C, to C alkoxy.

Many compounds have the required structure. The alkoxy groups are preferably methoxy or ethoxy, the alkyl group is preferably methyl or ethyl, the cycloalkyl group is preferably cyclohexyl, and the halogen is preferably chlorine. One commercially 15 available compound is the Ciba-Geigy product Irgacure 651 which has the formula:

Irgacure 184, also from Ciba-Geigy, is another useful acetophenone derivative, and it has the formula:

Still another commercially available useful acetophenone derivative is diethoxy acetophenone, available from Aldrich Chemical Company, Inc. Milwaukee, Wisconsin, which has the formula:

When the photoinitiator is a hydroxy- functional compound, one can define the useful acetophenone derivatives in a somewhat different manner. Thus, the hydroxyalkyl phenones which are preferred herein have the formula:

O

C - R° - OH

(V) R^c

^A^ in which R^b is an alkylene group containing from 2-8 carbon atoms and R^c is an optional hydrocarbon substituent containing from 1 to 10 carbon atoms and which may be alkyl or aryl, e.g., methyl, ethyl, butyl, octyl or phenyl.

It is particularly preferred that the hydroxy group be in the 2 position in which case it is preferably a tertiary hydroxy group which defines a hydroxy group carried by a carbon atom which has its remaining three valences connected to other carbon atoms. Particularly preferred compounds within which will be found the commercial material used to obtain the data discussed have the formula:

in which each R^d is independently an alkyl group containing from 1 to 4 carbon atoms. In the commercial product Darocur 1173, each R^d is methyl. This provides a compound which can be described as 2-hydroxy, 2-methyl, 1-phenyl propane 1-one. The "propane" is replaced by butane or hexane to describe the corresponding compounds, and these will further illustrate preferred compounds in this invention.

The benzoyl diary1 phosphine oxide photoinitiators which may be used herein have the formula:

In formula VII, each R^e is independently an optional hydrocarbon substituent containing from 1 to 10 carbon atoms and which may be alkyl or aryl as previously noted, and each n is independently an integer from 1 to 3. In preferred practice, a 2, ,6-trimethyl benzoyl compound is used, and the two aromatic groups connected to the phosphorus atom are phenyl groups. This provides the compound 2,4,6-trimethyl benzoyl diphenyl phosphine oxide which is available from BASF under the trade designation Lucirin. When it is desired to harden the cured coatings, this can be achieved by employing polyacrylates, like trimethylol propane triacrylate or epoxy resin diacrylates, or high T_g monoethylenic monomers, like N-vinyl pyrrolidone, N- vinyl caprolactam, isobornyl acrylate or methyl acrylate. These are used in combination with the previously described long chain alkyl acrylates in order to minimize water sensitivity.

Referring more particularly to the light which is used for cure, its wavelength can vary somewhat depending upon the photoinitiators which are used. In present practice, the light used is usually in the ultraviolet range which extends from about 200 nanometers to about 400 nanometers. However, light of longer wavelength can be used up to about 600 nanometers, preferably up to about 520 nanometers. The photoinitiators are normally present in an amount of from 0.5% to 10%, preferably from about 2% to 6%. Representative photoinitiators are aryl ketones, such as benzophenone, acetophenone, diethoxy acetophenone, benzoin, benzil, anthraquinone, and the like. The photoinitiator may be bound to a polymer, if desired. The aforementioned acetophenone derivatives and phosphine oxides are preferred when both a vinyl ether and maleate or fumarate are utilized. An alternative form of energy that cures the present compositions can be provided by an electron beam.

The amount of energy from the electron beam utilized to cure the compositions is preferably about 1 to about 10, more preferably about 2 to about 8, megarads per square centimeter. It is preferred that a film to be cured with an electron beam is blanketed with an inert gas, e.g., nitrogen, to reduce the oxygen present in the atmosphere surrounding the film.

A representative device for generating the electron beam is a CB-150 Lab Unit commercially available from Energy Science.

The coatings of this invention are normally free of volatile organic solvent, albeit a small amount up to about 5% of the coatings can be tolerated.

The water sensitivity of the cured coatings is important and is measured both by absorption and extraction, these two values being added together to provide a total value indicative of the sensitivity of the coating to water. Water absorption is measured by determining the amount of water which is absorbed upon 24 hour immersion in deionized water at 25^* C followed by drying at 25^* C. Water extraction is measured by determining the amount of material which is extracted from the film after 5 days recovery at room temperature and ambient humidity.

The invention is illustrated in the examples which follow. Example 1

1 mole of the commercial polybutadiene oligomer diol described previously (Nisso PB GI 1000) is reacted with 2 moles of isophorone diisocyanate and 2 moles of either 2-hydroxyethyl acrylate or 2 moles of hydroxybutyl vinyl ether. The reaction is carried out in conventional fashion using added isooctyl acrylate to control the viscosity and a temperature of about 60^* C in the presence of about 0.1 percent by weight of dibutyl tin dilaurate to speed the formation of urethane groups. The reaction is carried to completion, as indicated by the elimination of isocyanate functionality.

Photocured coatings containing the above oligomer together with enough additional octyl/decyl acrylate (a commercial mixture containing the two) to provide a coating viscosity of about 4600 centipoises are soft and characterized by unusually low moisture sensitivity and high hydrolytic and oxidative stability. 4% by weight of Irgacure 184, as described previously, is used as photoinitiator and the cure is obtained with about 1 Joule per square centimeter of ultraviolet light.

Unless otherwise specified, in the following Examples the amount of photoinitiator utilized was 4% by weight, the photoinitiator utilized was Irgacure 184 and the dosage of ultraviolet light utilized was about 1 Joule per square centimeter. Example 2

2 moles of Nisso PB GI 1000 are reacted with 4 moles of 2,2,4-trimethyl hexamethylene diisocyanate and 2 moles of 2-hydroxyethyl acrylate and 1 mole of polyoxypropylene diamine having a number average molecular weight of about 230 daltons to provide chain extension via the formation of urea groups. The reaction is carried out in conventional fashion using a temperature of about 60 degrees C in the presence of about 0.1%. by weight of dibutyl tin dilaurate to speed the urethane and urea forming reactions.

Photocured coatings containing the above oligomer together with enough additional octyl/decyl acrylate (a commercial mixture containing the two) to provide a coating viscosity of about 4600 centipoises, are soft to moderately hard and characterized by unusually low moisture sensitivity and high hydrolytic and oxidative stability. Example 3

1 mole of Nisso PB GI 1000 is reacted with 2 moles of the diepoxide Epon 828 which is a diglycidyl ether of bisphenol A having a number average molecular weight of about 390 daltons. The addition reaction is carried out at a temperature in the range of 100 to 120^* C in the presence of a Lewis acid (BF₃ etherate) and in the absence of diluent. Care should be taken to stop the reaction before it gels, and this is done by removing or neutralizing the etherate or by lowering the temperature. The reaction produces an hydroxy ether which is capped by esterifying the remaining epoxy groups with 2 moles of acrylic acid or with 2 moles of beta carboxyethyl acrylate. Photocured coatings containing the above oligomer together with enough additional octyl/decyl acrylate (a commercial mixture containing the two) and isobornyl acrylate (a high T_g monomer) to provide a coating viscosity of about 5500 centipoise (measured at room temperature) , are hard, and characterized by unusually low moisture sensitivity and high hydrolytic and oxidative stability. The cured coatings can be softened by using a smaller proportion of the diepoxide and a smaller proportion of the unsaturated acid or by increasing the proportion of long chain acrylate.

The liquid coating composition of this example is formulated by heating the oligomer reaction product, which is a semi-solid at room temperature, to 60 C followed by the addition of the above noted monomers to provide the specified viscosity. Irgacure 184 is used as the photoinitiator in an amount of 4% and 0.5% of Tinuvin 770 (a hindered amine light stabilizer) and 0.5% of Irganox 1035 (a hindered phenolic antioxidant) are added. These last two components are supplied by Ciba- Geigy Corporation. Example 4

1 mole of Nisso PB GI 1000 is reacted with 2 moles of phthalic anhydride and with 2 moles of the diepoxide Epon 828 which is a diglycidyl ether of bisphenol A having a number average molecular weight of about 390 daltons, the Epon 828 having been capped with 2 moles of acrylic acid or with 2 moles of carboxyethyl acrylate. The use of phthalic anhydride reduces the tendency toward gelation encountered in Example 3. Photocured coatings containing the above oligomer in admixture with the same monomers as in Example 3 are similar to those obtained in Example 3. The products exhibit good hydrolytic and high oxidative stability and are very insensitive to water. Example 5

1 mole of Nisso PB GI 1000 is reacted with 2 moles of maleic anhydride and the resulting carboxyl- functional diester is reacted with 2 moles of hydroxybutyl vinyl ether. The reactions are conventional esterification reactions.

Photocured coatings containing the above oligomer are similar to those obtained in Example 3.

The combination of maleic unsaturation and vinyl ether unsaturation photocures rapidly in the presence of photoinitiators of the character of Darocur 1173.

Example 6

2 moles of Nisso PB GI 1000 are reacted with 2 moles of phthalic anhydride and the addition reaction product so-obtained is combined with 3 moles of acrylic 22 acid and the mixture reacted with 1 mole of the epoxy cresol novolac resin ECN 1299.

Photocured coatings containing the above polyfunctional oligomer are similar to those obtained in Example 3, except the oligomers can vary in their physical character from low to high modulus depending on the ratio of carboxyl to hydroxyl to acrylic acid used. The water sensitivity is uniformly low.

Claims

WHAT IS CLAIMED IS:

1. A polymerizable ethylenically unsaturated oligomer which is an oligomeric ethylenically unsaturated reaction product of components comprising: (1) a polybutadiene oligomer carrying two reactive groups and lacking significant unsaturation, said oligomer containing at least about 60% by weight of butadiene polymerized in the 1,2-position with the balance of the butadiene polymerized in the 1,4-position and said oligomer being hydrogenated to remove much of the residual unsaturation therefrom and having a number average molecular weight of from about 500 to about 5,000 daltons; and

(2) a monofunctional ethylenically unsaturated compound, said unsaturated oligomer having a number average molecular weight of from about 1,000 to about 10,000 daltons and containing at least about 40% by weight of said polybutadiene oligomer.

2. A polymerizable ethylenically unsaturated oligomer which is an oligomeric ethylenically unsaturated reaction product of components comprising:

(1) a polybutadiene oligomer carrying two reactive groups and lacking significant unsaturation, said oligomer containing at least about 60% by weight of butadiene polymerized in the 1,2-position with the balance of the butadiene polymerized in the 1,4-position and said oligomer being hydrogenated to remove much of the residual unsaturation therefrom and having a number average molecular weight of from about 500 to about ^• 5,000 daltons;

(2) a molar excess of an organic compound having a plurality of groups reactive with the two functional groups of said difunctional oligomer to provide reactive terminal groups; and (3) a monofunctional ethylenically unsaturated compound which is reactive with the said reactive terminal groups, said unsaturated oligomer having a number average molecular weight of from about 1,000 to about 10,000 daltons and containing at least about 40% by weight of said polybutadiene oligomer.

3. An unsaturated oligomer as recited in claim 2 in which said monofunctional ethylenically unsaturated compound is selected from the group consisting of monofunctional (meth)acrylates and monofunctional vinyl ethers and carboxylates.

4. The unsaturated oligomer as recited in claim 3 wherein the carboxylates are selected from the group consisting of makeates and fumarates.

5. An unsaturated oligomer as recited in claim 2 in which said polybutadiene oligomer is a diol and the monofunctionality in said monofunctional ethylenically unsaturated compound is hydroxy functionality.

6. An unsaturated oligomer as recited in claim 5 in which said polybutadiene oligomer diol contains from 75% to 90% of butadiene polymerized in the 1,2 position.

7. An unsaturated oligomer as recited in claim 2 in which said organic compound containing a plurality of reactive groups is difunctional, said monofunctional compound is a (meth)acrylate and said unsaturated oligomer has a number average molecular weight of from 1,500 to 5,000 daltons.

8. An unsaturated oligomer as recited in claim 7 in which said difunctional organic compound is an organic diisocyanate and said monofunctional (meth)acrylate is a monohydric acrylate.

9. An unsaturated oligomer as recited in claim 7 in which said difunctional organic compound is an anhydride.

10. An unsaturated oligomer as recited in claim 9 in which said difunctional compound is a dicarboxylic acid anhydride and said monofunctional (meth)acrylate is a monohydric acrylate.

11. An unsaturated oligomer as recited in claim 9 in which said difunctional compound is a diepoxide and said monofunctional (meth)acrylate is a monocarboxylic acid.

12. An unsaturated oligomer as recited in claim 11 in which said monocarboxylic acid is acrylic acid.

13. A polymerizable composition comprising the unsaturated oligomer of claim 1 in compatible admixture with sufficient ethylenically unsaturated liquid to provide coating viscosity, said ethylenically unsaturated liquid comprising an alkyl (meth)acrylate in which the alkyl group contains at least 6 carbon atoms.

14. A polymerizable composition as recited in claim 13 in which said alkyl group contains 8 to 12 carbon atoms, the monofunctional compound comprises a vinyl ether and a maleate or fumarate and the composition further comprises a photoinitiator selected from the group consisting of hydroxy- or alkoxy- functional acetophenone derivatives and benzoyl diaryl phosphine oxides.

15. • A polymerizable composition as recited in claim 13 in which said polybutadiene oligomer is a diol and is reacted with an organic diisocyanate and a monohydric acrylate.

16. A polymerizable composition as recited in claim 15 in which said composition contains at least 50% of said unsaturated oligomer.

17. A polymerizable composition as recited in claim 13 in which said polybutadiene oligomer is a diol and is reacted with an anhydride.

18. A polymerizable composition as recited in claim 17 in which said anhydride is a dicarboxylic acid anhydride and said monofunctional (meth)acrylate is a monohydric acrylate.

19. A polymerizable composition as recited in claim 17 in which said anhydride is a diepoxide and said monofunctional- (meth)acrylate is a monocarboxylic acid.

20. A polymerizable composition as recited in claim 19 in which said monocarboxylic acid is acrylic acid and said composition contains from 45% to 55% of said unsaturated oligomer.

21. The composition in accordance with claim

13 wherein the monofunctional compound is selected from the group consisting of: (1) (meth)acrylates; and (2) vinyl ethers, maleates or fumarates.

22. An optical glass fiber coated with a cured coating of the polymerizable coating of claim 13.

23. An optical glass fiber prime-coated with a cured coating of the polymerizable coating of claim 15.

24. An optical glass fiber secondary-coated with a cured coating of the polymerizable coating of claim 19.

25. A cable structure wherein fibers are bound together with a cured coating of the polymerizable coating of claim 13.

26. A polymerizable ethylenically unsaturated oligomer which is an oligomeric ethylenically unsaturated reaction product of components comprising:

(1) a polybutadiene oligomer carrying two reactive groups and lacking significant unsaturation, said oligomer containing at least about 60% by weight of butadiene polymerized in the 1,2-position with the balance of the butadiene polymerized in the 1,4- position, said oligomer being hydrogenated to remove much of the residual unsaturation therefrom having a number average molecular weight of from about 500 to about 5,000 daltons;

(2) an ethylenically unsaturated compound selected from the group consisting of (meth)acrylates and monofunctional vinyl ethers, maleates or fumarate; said unsaturated oligomer having a number average molecular weight of from about 1,000 to about 10,000 daltons and containing at least about 40% by weight of said polybutadiene oligomer.

27. The unsaturated oligomer in accordance with claim 26 further comprising a photoinitiator selected from the group consisting of hydroxy- or alkoxy-functional acetophenone derivatives and benzoyl diaryl phosphine oxides.

28. A polymerizable ethylenically unsaturated oligomer which is an oligomeric ethylenically unsaturated reaction product of components comprising:

(1) a polybutadiene oligomer having two reactive groups and lacking significant unsaturation, said oligomer containing at least about 60% by weight of butadiene polymerized in the 1,2-position with the balance of the butadiene polymerized in the 1,4-position and said oligomer being hydrogenated to remove much of the residual unsaturation therefrom and having a number average molecular weight of from abut 500 to about 5,000 daltons;

(2) a monofunctional ethylenically unsaturated compound selected from the group consisting of (meth)acrylates and vinyl ether, maleate or fumarate which is reactive with the said reactive terminal groups; and said unsaturated oligomer having a number average molecular weight of from about 1,000 to about 10,000 daltons and containing at least about 40% by weight of said polybutadiene oligomer.

29. The unsaturated oligomer in accordance with claim 28 further comprising a photoinitiator selected from the group consisting of hydroxy- or alkoxy-functional acetophenone derivatives and benzoyl diaryl phosphine oxides.