CA2153581A1

CA2153581A1 - Radiation-curable oligomers and liquid, radiation-curable coating composition for coating glass surfaces

Info

Publication number: CA2153581A1
Application number: CA002153581A
Authority: CA
Inventors: Horst Hintze-Bruning; Martin Lobert
Original assignee: Individual
Current assignee: BASF Farben und Fasern AG
Priority date: 1993-01-28
Filing date: 1994-01-20
Publication date: 1994-08-04
Also published as: EP0681562A1; WO1994017005A1; JPH08509252A; DE4302327A1; AU672672B2; NO952979D0; FI953577A; FI953577A0; TW249818B; BR9405817A; AU5884894A; BG99789A; KR960700201A; NO952979L

Abstract

The present invention relates to radiation-curable oligomers which can be prepared from polyether-triols or -triamines a, polyetherdiols or -diamines b, OH-functional acrylate monomers c and diisocyanates d, the molar ratio of a to b being between 0.1 to [sic]
1.1, the molar ratio of c to a being between 2.0 and 10 and the ratio of equivalents of the NCO groups of d to the hydroxyl and/or amino groups in the sum of a to c being between 0.9 and 1.0, characterized in that the oligomers have been prepared by employing at least one compound having 3 to 4 amino groups and having a number-average molecular weight of more than 4000 to 10,000 and/or at least one compound having 2 amino groups and having a number-average molecular weight of more than 4000 to 10,000, and in that the oligomers have double bond contents of from 0.25 to 0.44 mol/kg.

Description

` 21~3S81 21.01.1993/fe FILE, ~N ~N TH~S ~iL~D!-7EXT TRAN~LATION
1460z BASF Lacke + Farben Aktieng~ lschaft Radiation-curable oligomer~ and liquid, radiation-curable coatinq com~o~ition for coatinq glas~ surface~

The present invention relates to radiation-curable oligomers having two or more ethyle~;c~lly unsaturated end y uu~ and two or more urea and possibly urethane groups per molecule, which oligomers can be prepared from a) at least one hydroxy- and/or amino-functional com-pound with a functionality of between 3 and 4, b) at least one compound with 2 hydroxyl and/or amino groups per molecule, c) at least one monoethylenically unsaturated com-pound with a group having one active hydrogen atom per molecule and with a number-average molecular weight of between 116 and 1000, and d) at least one ~lirh~tic and/or cycloaliphatic diisocyanate, components a to d being employed in amounts such that 1.) the molar ratio of component a to component b is between 0.1:1 and 1.1:1, - 21~i3581

2.) the molar ratio of component c to component a is between 2:1 and 10:1, and

3.) the ratio of equivalents of the isocyanate groups of component d to the ~;no and po6sibly hydroxyl 5groups in the sum of components a to c is between 0.9 and 1Ø

The present invention also relates to radia-tion-curable coating compositions contA i n i ng these radiation-curable oligomers and to processes for coating glass surfaces, especially optical glass fibers, in which these coating compositions are employed.
Optical glass fibers have g~;ne~ cont;nl~Ally increasing importance in the communications sector as optical waveguide fibers. For this application it i8 absolutely necessary to protect the glass surface from moisture and wear phenomena. Consequently the glass fibers are provided directly after their production with at least one protective coating.
Thus it is known from EP-B-114 982, for example, to provide glass fibers initially with a buffer coat (primer) which is elastic but not very hard and not very tough, based on linear urethane acrylates, and subsequently to apply a radiation-curable topcoat which is likewise based on linear urethane acrylates and which is of high hardness and toughness. The two-coat structure is inten~e~ to provide protection to the glass fibers under mechAn;cAl loading, even at low 215~5%1 temperatures. However, coatings based on l; n~Ar urethane acrylates have the disadvantage that the mechAn i ~A l properties of the coatings, especially their elasticity, are still in need of improvement.
Furthermore, EP-A-223 086 also discloses radia-tion-curable coating compositions for coating optical glass fibers. These coating compositions contain as binder radiation-curable oligomers which can be pre-pared from polyethertriols or -triamines having an average molecular weight of from 300 to 4000, polyetherdiols or -di~mines having an average molecular weight of from 200 to 4000, OH-func~ionAl acrylate monomers and Ai i ~ocyanates, where the oligomers are prepared employing a molar ratio of triol or tri~m;ne to diol or diamine of between 2.5:1 and 20:1.
These radiation-curable coating compositions described in EP-A-223 086 are employed either as a topcoAt or as a one-coat finish. As a primer, however, they are unsuitable because the fully cured coatings have an excessive modulus of elasticity.
EP-A-209 641 also describes radiation-curable coating compositions for coating optical glass fibers.
These coating compositions contain as hi nAer a polyurethane oligomer with acrylate end groups which is based on a polyfunctional core. These coating composi-tions can be used both as primer and as topcoat. One-coat processing is also possible.
The international patent application with the Publication Number WO 92/04391 discloses radiationcurable coating compositions for coating optical glass fibers, which contain as hi n~Pr radiation-curable oligomers in accordance with the precharacterizing clause of the main claim. Rec~llse of their low modulus of elasticity, these coating compositions are employed in particular as primers for glass fibers. However, the manufacturers of optical glass fibers require a further improvement in the mech~nical properties of the coatings. In particular, the buffer action of the coatings should be optimized further, and the buffer properties should remain as constant as possible over a broad temperature range. At the same time, the reactivity of the coating compositions should not be impaired and the ease of assembly of the coated glass fibers ghould be ensured.
The object on which the present invention is based is to provide radiation-curable coating composi-tions for coating glass surfaces, especially optical glass fibers, which lead to coatings having properties which are improved in comparison with the known coating compositions. In particular, the fully cured coatings should exhibit an improved buffer action through lower moduli of elasticity at higher elongations at break, and the buffer properties should remain approximately the same over as great a temperature range as possible.
This means that any impairment of the mec~n;cal properties of the coating as the temperature falls should be minimized. In particular, there should only be a minimal increase in the modulus of elasticity as - 21~358~

the temperature falls. At the same time the coating compositions should cure fully as quickly as possible.
Moreover, the coating compositions should enable improved assembly of the coated glass fibers. It is therefore necessary, especially at the junctions between different glass fibers, that the coatings have a reduced adhesion to the glass fiber so that they can be removed easily in the junction area. On the other hand, however, the adhesion of the coating to the glass fiber should not deteriorate excessively on exposure to moisture, in order to ensure that no delamination occurs by exposure to moisture as the optical fibers age.
The object is surprisingly achieved by radia-tion-curable oligomers with two or more ethyle~;cAlly unsaturated end groups and two or more urea and possibly urethane groups per molecule, which can be prepared from a) at least one hydroxy- and/or amino-functional com-pound with a functionality of between 3 and 4, b) at least one compound with 2 hydroxyl and/or amino yLou~s per molecule, c) at least one monoethyle~; CA lly unsaturated com-pound with a group having one active hydrogen atom per molecule and with a number-average molecular weight of between 116 and 1000, and d) at least one Al;rhAtic and/or cycloaliphatic diisocyanate, components a to d being employed in amounts such that 1. the molar ratio of component a to component b iB
between 0.1:1 and 1.1:1, preferably between 0.1 and 0.8, 2. the molar ratio of component c to component a is between 2.0:1 and 10:1, preferably between 2.5 and 10, and 3. the ratio of equivalents of the isocyanate groups of component d to the A~; no and possibly hydroxyl groups in the sum of components a to c is between 0.9 and 1Ø

The radiation-curable oligomers are characterized in that 1.) as component a at least one amino group-contAin;ng compound a1 having a number-average molecular weight of more than 4000 to 10,000 and/or at least one amino and/or hydroxyl ylG~ _OllLA; n; ng com-pound a2 having a number-average molecular weight of from 400 to 4000 has been employed, 2.) as component b at least one amino grGu~ _o~lt~in;nq compound bl having a number-average molecular weight of more than 4000 to 10,000 and/or at least one amino and/or hydroxyl ylou~ ~ont~;n;ng com-pound b2 having a number-average molecular weight of from 200 to 4000 has been employed, - 21~3581 3.) the oligomers have double bond contents of from 0.25 to 0.44 mol/kg, and

4.) in the preparation of the oligomers at least one amino group-contA; n i ng compound a1 and/or bl has been employed.

The present invention also relates to radiation-curable coating compositions contA; n; ng these radiation-curable oligomers, and to processes for coating glass surfaces, especially optical glass fibers, in which these coating compositions are employed.
It is surprising and was not foreseeable that radiation-curable coating compositions based on the oligomers according to the invention lead to coatings having a buffer action which is improved in relation to conventional coatings, i.e. having lower moduli of elasticity coupled with greater elongations at break. A
further advantage is a good buffer action of the coatings even at low temperatures, since this solves the problem of so-called microflexions. The coatings according to the invention are further distinguished by good mechAn;sAl properties, such as, for example, elon-gation and tensile strength adapted to the application, and by reduced adhesion of the coatings to the glass fiber, enabling improved assembly of the coated glass fibers. At the same time the adhesion of the coating does not deteriorate excessively after exposure to moisture, so that it is ensured that no delAm;nation - 2153S~ 1 exposure to moisture as the optical fibers age.
Finally, the coating compositions according to the invention are quick to cure fully.
There now follows a closer description, initially, of the radiation-curable oligomers according to the invention:
It i8 essential to the invention that the oligomers are prepared employing amino ylOU~ ~ontAining componn~R al having a functionality of from 3 to 4 and having a number-average molecular weight of more than 4000 to 10,000, preferably of more than 4000 to 6000, and/or difunctional, amino group-contAining compounds bl having a number-average molecular weight of more than 4000 to 10,000, preferably of more than 4000 to 6000. The componn~ preferably employed as component a1 and/or component b1 are those having secondary amino groups, in particular polyethers having terminal, secondary ~mi no groups. Particular preference is given to the employment, as component a1, of polyalkoxylated triols having terminal, secondary amino groups.
Examples of compounds which are suitable as component a1 and have primary amino groups are the amino-func-tional componn~ derived from polyalkoxylated triols, for example the products which are commercially available from Texaco under the name JEFFAMIN~, e.g.
JEFFAMIN~ T 5000.
The secondary amines employed as component al can be prepared, for example, by reacting the corresponding polyethers, cont~ining primary amino groups, with `- 21~3581 g Al;ph~tic ketones such as, in particular, methyl isobutyl ketone and subsequently hydrogenating the resulting ketimine. Examples of polyethers which con-tain primary amino groups and are suitable for this reaction are the products available from Texaco under the name JEFFAMIN0, such as JEFFAMIN0 T 50OO.
Also suitable as component al are the products commercially available from roN~ Chemie Gmb~ under the name NOVAMIN~, e.g. NOVAMIN~ N 60.
Examples of compo~nA~ employed a~ component bl are the amino-functional compo~ln~ available from Texaco under the name JEFFAMIN0 and derived from polyalkoxylated diols, such as, for example, JEFFAMIN0 D 4000. The Ee-Qn~ry amines employed as component bl can be prepared analogously to the compounds al by reacting the correspon~i ng polyethers which contain primary amino groups with aliphatic ketones such as, in particular, methyl isobutyl ketone and subsequently hydrogenating the resulting ketimine. Examples of polyethers which contain primary amino groups and are suitable for this reaction are the JEFFAMIN0 grades listed under bl.
Also suitable as component bl are the products commercially available from coNn~A Chemie Gmb~ under the name NOVAMIN~, e.g. NOVAMIN~ N 50.
It iæ particularly preferred to employ as com-ponent b1 polyalkoxylated diols having terminal, secondary amlno groups.

It is also possible if desired, for the preparation of the oligomers according to the inven-tion, to employ further amino and/or hydroxyl group-contAining compounds a2 having a functionality of from 3 to 4, preferably 3, and having a number-average molecular weight of from 400 to 4000, preferably from 750 to 2000.
Examples of suitable amino and/or hydroxyl group-contAining compounds a2 are polyoxyalkylated triols, for example ethoxylated and plG~uxylated triols, preferably ethoxylated triols particularly preferably having a number-average molecular weight of greater than or equal to 1000. Examples of triols which are employed are glycerol or trimethylolpropane.
Also suitable as component a2 are the correspon~ing amino-functional compounds, for example the amino-func-tional compounds derived from polyalkoxylated triols.
Examples are the products available from Texaco under the name JEFFAMIN~, for example JEFFAMIN~, T 403 and T 3000 and the products available from coNn~ Chemie GmbH under the name NOVAMIN~, e.g. NOVAMIN~ N 30.
In this context the ~mi no-functional compounds a2 may contain both prim~ry and secondary ~mi no groups.
Suitable compounds in addition to these are also those contA;n;ng both amino and hydroxyl groups.
It is also possible if desired, for the preparation of the oligomers accor~ing to the inven-tion, to employ further amino and/or hydroxyl - 21~3~81 group-contAining compounds b2 contAining two hydroxyl and/or amino groups per molecule.
These compounds b2 have number-average molecular weights of from 200 to 4000, preferably from 600 to 2000.
Examples of suitable amino and/or hydroxyl group-contAining compo~ln~C b2 are polyoxyalkylene glycols and polyoxyalkylenediamines, in which alkylene groups contAin;ng from 1 to 6 C atoms are preferred.
Suitable examples are thus polyoxyethylene glycols having a number-average molecular weight of 1000, 1500, 2000 or 2500 and polyoxypropylene glycols having the corresponding molecular weights, and polytetramethylene glycols. Polyethoxylated and polypropoxylated diols can also be employed, for example the ethoxylated or propoxylated derivatives of butanediol, hexanediol etc.
It is also possible to employ polyesterdiols which can be prepared by, for example, reacting the glycols already mentioned with dicarboxylic acids, preferably aliphatic and/or cycloAl;rhAtic ~;~Arho~ylic acids, for example hexahydrophthAl;c acid, adipic acid, azelaic, sebacic and glutaric acid and/or their alkyl-substi-tuted derivatives. Instead of these acids it is also possible to use their anhydrides where these exist.
Polycaprolactonediols can also be employed.
These products are contained [sic] by, for example, reacting an ~-caprolactone with a diol. Products of this kind are described in US-A 3 169 945.

- 21535~ 1 The polylactonediols obtained by this reaction are distinguished by the presence of a terminal hydroxyl group and by recurring polyester units derived from the lactone. These recurring molecular units may conform to the formula - C - (CHR)n ~ C~2 in which n is preferably from 4 to 6 and the sub-stituent is hydrogen, an alkyl rA~icAl~ a cycloalkyl rA~icAl or an alkoxy rA~iCAl~ no substituent con~Aining more than 12 carbon atoms and the total number of carbon atoms of the substituents in the lactone ring not exceeding 12.
The lactone used as starting material may be any desired lactone or any desired combination of lactones, and said lactone should contain at least 6 carbon atoms in the ring, for example from 6 to 8 carbon atoms, and there should be at least 2 hydrogen substituents on the carbon atom. The lactone used as starting material may be represented by the following general formula:

CH2--(CR2)n ~C 0 in which n and R have the meaning already ; nA; c~ted.
The lactones which are preferred in the invention, for the preparation of the polyesterdiols, are the capro-lactones in which n has the value 4. The most preferred lactone is the substituted ~-caprolactone in which n has the value 4 and all the substituents R are hydrogen. This lactone is particularly preferred because it is available in large quantities and gives coatings having excellent properties. It is also possible to make use of various other lactones, individually or in combination. Examples of Al ;phAtic diols which are suitable for the reaction with the lactone are the diols already listed above for the reaction with the carboxylic acids.
It is of course also possible to employ as com-ponent b2 the corresponding diamines and compounds having an OH and an amino group. Bxamples of suitable compounds are the products available from Texaco under the name JEFFAMIN~ D 230, D 400, D 2000, ED 600, 2153~81 ED 900, ED 2001, ED 4000, BUD 2000 and C 346 and the products available from CONDEA Chemie GmbH under the name NOVAMIN~, e.g. NOVAMIN~ N 10, N 20 and N 40.
It is preferred to employ aæ component b2 a mixture of b21) from 0 to 90 mol% of at least one polyetherdiol and b22) from 10 to 100 mol% of at least one modified polyetherdiol composed of ~) at least one polyetherdiol ~) at least one aliphatic and/or cycloAl;phAtic dicarboxylic acid and5 7) at least one aliphatic, saturated compound havingone epoY;~e group and having from 8 to 21 C atoms per molecule, the sum of the proportions of components b21 and b22 and the sum of the proportions of components ~ to 7 being in each case 100 mol%.
To prepare the modified polyetherdiol~ by con-ventional methods components ~ to 7 are employed in amounts such that the ratio of equivalents of the O~
groups of component ~ to the carboxyl groups of component ~ is between 0.45 and 0.55, preferably 0.5, and the ratio of equivalents of the epoxide groups of component 7 to the carboxyl groups of component ~ is between 0.45 and 0.55, preferably 0.5.

21~i35~

Examples of suitable polyetherdiols b21 and ~
are the polyoxyalkylene glycols already listed, in which the alkylene groups have from 1 to 6 C atoms. In this context it i8 preferred to employ as component b21 polyoxypropylene glycols having a number-average molecular weight of between 600 and 2000. As component it is preferred to employ polyoxybutylene glycols (poly-T~F) having a number-average molecular weight > 1000.
The Alip~Atic and cycloaliphatic dicarboxylic acids which it i~ preferred to employ as component are those having from 8 to 36 C atoms per molecule, for example hexahydrophthalic acid. Suitable examples for component ~ are erQy; ~ized, monoolef; n; ~A 1 1 y unsaturated fatty acids and/or polybutadienes.
It i8 preferred to employ as component glycidyl e~ter~ of branched monocarboxylic acids, for example the glycidyl ester of versatic acid.
The compolln~ a1, a2, b1 and b2 are preferably employed in amounts such that the molar ratio of the hydroxyl and/or amino groups of components a2 and b2 to the amino groups of components a1 and bl is between 0 and 10, preferably between 0.1 and 3.
The compound~ employed to introduce the ethylen;~Ally unsaturated groups into the polyurethane oligomer are monoethyle~icAlly unsaturated compounds having one group contA;ning an active hydrogen atom, which have a number-average molecular weight of from 116 to 1000, preferably from 116 to 400. Examples of at~3~s ~
-suitable components c which may be mentioned are, for example, hydroxyalkyl esters of ethylen; ~A 1 1 y unsaturated carboxylic acids, for example hydroxyethyl acrylate, hydroxypropyl acrylate, hydluxybuLyl acrylate, hydroxyamyl acrylate, hydroxyhexyl acrylate and hydroxyoctyl acrylate, and the corresponding hydroxyalkyl esters of methacrylic, fumaric, maleic, itaconic crotonic and isocrotonic acid, but with the hydroxyalkyl esters of acrylic acid being preferred.
Also suitable as component c are adducts of caprolactone and one of the abovementioned hydroxyalkyl esters of ethylen; rA 11y unsaturated carboxylic acids-It is preferred to employ adducts of hydroxyalkyl esters of acrylic acid having a number-average molecular weight of from 300 to 1000.
Suitable as component d for the preparation of the oligomers according to the invention are Al ;phAtiC
and/or cycloaliphatic diisocyanates, for example 1,3-cyclopentane, 1,4-cyclohexane and 1,2-cycloheYAne diisocyanate, 4,4'-methylenebis(cyclohexyl isocyanate) and isophorone ~ ocyanate, trimethylene, tetra-methylene, pentamethylene, hexamethylene and trimethyl-hexamethylene 1,6-diisocyanate and the diisocyanates described in EP-A-204 161, column 4, lines 42 to 49 and are derived from dimeric fatty acids.
Isophorone diisocyanate and trimethylhexa-methylene 1,6-diisocyanate are preferably employed.
Components a to d are employed for the prepara-tion of the oligomers in amounts such that .

1. the molar ratio of component a to component b is between 0.1:1 and 1.1:1, preferably between 0.1 and 0.8, 2. the molar ratio of component c to component a is 5between 2.0:1 and 10:1, preferably between 2.5 and 10, and 3. the ratio of equivalents of the isocyanate groups of component d to the active hydrogen atoms of components a plus b plus c is between 0.9 and lØ
The oligomers according to the invention can be prepared in various ways. For instance, it is possible for example first to react the diisocyanate d with the chain-lengthening agents a and b and subsequently to react the remaining free isocyanate groups with the ethylenically unsaturated compound c.
It is also possible to prepare the oligomers by first reacting some of the isocyanate groups of component d with the ethylenically unsaturated compound c and by subsequently reacting the remaining free isocyanate groups with the chain-lengthening agents a and b.
It is also possible to prepare the polyurethane oligomers by the processes described on page 5 of 25EP-A-223 086.
The polyurethane oligomers are preferably pre-pared by means of a two-stage process in which first of all the stoichiometric polyaddition of components a to d is carried out until more than 85% of the NC0 groups of component d have reacted. In this first proce~s step, components a to d are employed in amounts such that the ratio of equivalents of the NCO groups of com-ponent d to the active hydrogen atoms of component6 a to c is 1:1.
In a second process step, the remainder of the other components (corresponding to the desired NCO: OH
ratio) is then added and the reaction i8 continued up to a conversion of the NCO groups of > 99%. In this second process step it is preferred to add further com-ponent c and to adjust the desired NCO:OH ratio of equivalents by adding this component c. In this preferred two-stage process, it is preferred to employ as component c an adduct of hydroxyethyl acrylate and caprolactone having a number-average molecular weight of ~ 300.
It is essential to the invention that the urethane oligomers have double bond contents of from 0.25 to 0.44 mol/kg, preferably from 0.3 to 0.44 mol/kg. Furthermore, the urethane oligomers according to the invention generally have number-average molecular weights of from 2000 to 20,000, preferably from 3500 to 16,000 (measured by GPC against polystyrene stAn~Ard), weight-average molecular weights of from 8000 to 100,000, preferably from 10,000 to 40,000 (measured by GPC against polystyrene stAn~rd) and a functionality of from 2 to 4, preferably from 2.5 to 3.0, in each case per statistical average polymer molecule.

The oligomers according to the invention are employed as film-forming component A in radiation-curable coating compositions. The coating compositions conventionally contain from 10 to 78% by weight, preferably at least 15% by weight and particularly preferably from 63 to 73% by weight, based in each case on the total weight of the coating composition, of these oligomers according to the invention.
As a further component, the coating composi-tions may contain from 0 to 60% by weight, preferablyfrom 0 to 50~ by weight, based in each case on the total weight of the coating composition, of at least one further ethyl~nic~lly unsaturated oligomer B. In addition to unsaturated polyesters, polyester acrylates and acrylate copolymers it is above all urethane acrylate oligomers which are employed, with the excep-tion of the urethane acrylate oligomers employed as component A. The properties of the fully cured coating can be controlled specifically by the nature and amount of this component B. The higher the proportion of this component B, the higher in general the modulus of elas-ticity of the fully cured coating. Component B is con-sequently added to the coating compositions in particular when the coating compositions are employed as topcoat. The effect of this component B on the properties of the resulting coating is, however, known to those skilled in the art. The most favorable amount to be used in each case can therefore be readily deter-mined on the basis of a few routine experiments. These 21~3581 -ethylen;rAlly unsaturated polyurethanes which are employed as component B are known. They can be obtA;ne~
by reacting a di- or polyisocyanatate with a chain-lengthe~;ng agent from the group comprising diols/polyols and/or diamines/polyamines and sub-sequently reacting the remaining free isocyanate groups with at least one hydroxyalkyl acrylate or hydroxyalkyl ester of other ethylen;cAlly unsaturated carboxylic acids.
In this context, the amounts of chain-lengthening agent, di- or polyisocyanate and hydroxyalkyl ester of an ethylen;cAlly unsaturated carboxylic acid are chosen such that 1. the ratio of eguivalents of the NCO groups to the reactive groups of the chain-lengthen;ng agent (hydroxyl, amino and/or mercaptyl tsic] groups) is between 3:1 and 1:2, preferably 2:1, and 2. the OH groups of the hydroxyalkyl esters of the ethylen;c~lly unsaturated carboxylic acids are present in a stoichiometric guantity in relation to the remaining free isocyanate groups of the prepolymer composed of isocyanate and chain-lengthening agent.
It is furthermore possible to prepare the polyurethanes B by first reacting some of the isocyanate groups of a di- or polyisocyanate with at least one hydroxyialkyl [sic] ester of an ethyle~;rAlly unsaturated carboxylic acid and then by reacting the remaining isocyanate groups with a chain-lengthç~ing agent. In this case, too, the amounts of chain-lengthen;ng agent, isocyanate and hydroxyalkyl ester of unsaturated carboxylic acids are chosen such that the ratio of equivalents of the NCO groups to the reactive group of the chain-lengthening agent is between 3:1 and 1:2, preferably 2:1, and the ratio of equivalents of the remaining NCO groups to the OH groups of the hydroxylalkyl ester is 1:1.
Additional possibilities are of course all intermediate forms of these two processes. For example, some of the isocyanate groups of a diisocyanate can first be reacted with a diol, subsequently some more of the isocyanate groups can be reacted with the hydroxyalkyl ester of an ethylenir~lly unsaturated carboxylic acid, and following this the remaining isocyanate groups can be reacted with a diamine.
The~e various preparation processes of the polyurethanes are known (cf. for example EP-A-294 161) and consequently require no more detailed description.
Compo~ln~s which are suitable for the prepara-tion of these urethane acrylate oligomers B are the compounds already employed in the preparation of com-ponent A, and also the compounds mentioned in DE-A 38 40 644.
Especially when using the coating compositions according to the invention as a topcoat, it is pre-ferred to employ aromatic structural components for the preparation of the urethane acrylate oligomers. Parti-cularly preferred in this case are 2,4- and 2,6-toluylene diisocyanate as isocyanate component and aromatic polyesterpolyols based on phth~lic acid and isophthalic acid and/or polypropylene glycol, ethlyene tsic] glycol and diethylene glycol as chain-lengthening agents.
As a further component, the radiation-curable coating compositions also contain at least one ethyle~icAlly unsaturated monomeric and/or oligomeric compound C, generally in a quantity of from 20 to 50%
by weight, preferably from 22 to 35% by weight, based in each case on the total weight of the coating compo-sition.
15By the addition of this ethylenically unsaturated compound C the viscosity and the curing rate of the coating compositions and the mechAn; ~Al properties of the resulting coating are controlled, as is fA~iliar to those skilled in the art and described 20in, for example, EP-A-223 086, to which reference is made in respect of further details.
Examples which may be mentioned of monomers which can be employed are ethoxyethoxyethyl acrylate, N-vinylcaprolactam, N-vinylpyrrolidone, rhennYyethyl acrylate, dimethylaminoethyl acrylate, hydroxyethyl acrylate, butoxyethyl acrylate, isobornyl acrylate, dimethylacrylamide and dicyclopentyl acrylate. Also suitable are di- and polyacrylates, for example butane-diol diacrylate, hexanediol diacrylate, trimethylol-215~581 propane di- and triacrylate, pentaerythritol tri- and tetraacrylate, the analogous acrylates of alkoxylated, in particular ethoxylated and propoxylated, polyols, for example glycerol, trimethylolpropane and penta-erythritol, having a number-average molecular weight of from 266 to 1014, and the long-chain 1 in~r diacrylates described in EP-A-250 631 and having a molecular weight of from 400 to 4000, preferably from 600 to 2500. The two acrylate groups may, for example, be separated by a polyoxybutylene structure. It i8 also possible to employ 1, 12-dodecyl diacrylate and the reaction product of 2 moles of acrylic acid with one mole of a dimeric fatty alcohol which in general has 36 C atoms.
Also suitable are mixtures of the monomers just described. It is preferred to employ phenoxyethyl acrylate, hey~neAiol diacrylate, N-vinylcaprolactam and tripropylene glycol diacrylate.
The photoinitiator, conventionally employed in the coating compositions according to the invention in an amount of from 2 to 8% by weight, preferably from 3 to 5% by weight, based on the total weight of the coating composition, varies with the radiation which is employed to cure the coating compositions ( W radia-tion, electron beam, visible light). The coating compo-sitions according to the invention are preferably curedusing W radiation. In this case, it is usual to employ photoinitiators based on ketones, for example aceto-phenone, benzophenone, ~,~-dimethyl-u-hydroxyaceto-phenone, diethoxyacetophenone, 2-hydroxy-2-methyl-21~35~ 1 1-phenylpropan-1-one, hydroxypropyl phenyl ketone, m-chloroacetophenone, propiophenone, benzoin, benzil, benzil dimethyl ketal, anthraquinone, thioxanthone and thioxanthone derivatives and triphenylphosphine and the like, and also mixtures of different photoinitiators.
In addition, coating compositions may if desired also contain conventional auxiliaries and addi-tives. These are employed conventionally in an amount of from 0 to 4% by weight, preferably from 0.5 to 2.0%
by weight, based in each case on the total weight of the coating composition. Examples of such substances are leveling agents and plasticizers.
The coating compositions can be applied to the substrate using known application methods, for example spraying, rolling, flow coating, immersion, knife coating or brushing.
The coating films are cured using radiation, preferably using UV radiation. The apparatus and condi-tions for these curing methods are known from the literature (cf. e.g. R. Holmes, U.V. and E.B. Curing Formulations for Printing Inks, Coatings and Paints, SITA Technology, Academic Press, Ton~o~, United Rindom [sic] 1984) and require no further description.
The coating compositions are suitable for coating a variety of substrates, for example glass, wood, metal and plastic surfaces. However, they are employed in particular for coating glass surfaces, especially preferably optical glass fibers.

` 2153~81 The present invention therefore also relates to a process for coating a glass surface, in which a radiation-curable coating composition is applied and is cured by means of W radiation or electron beams, which is characterized in that the coating compositions according to the invention are employed as radiation-curable coating composition.
The process according to the invention is particularly well suited to the coating of optical glass fibers. In thi6 context the coating compositions according to the invention may be applied to the glass fibers, in particular, as primer, but if desired also as the topcoat of a two-coat finish. When using the coating compositions as primer, the fully cured coatings usually have a modulus of elasticity (at 2.5%
elongation and room temperature) of less than 10 NPa.
When using the coating compositions as topcoat, the fully cured coatings usually have a modulus of elasticity (at 2.5% elongation and room temperature) of from 500 to 1000 NPa.
The invention is illustrated in more detail in the following examples. All data on parts and percen-tages are data by weight, unless expressly stated otherwise.
Preparation of a modified polyetherdiol In a vessel fitted with stirrer, inert gas inlet and thermal sensor, 51.1 parts of polytetra-hydrofuran having a number-average molecular weight of 215~&1 1000 and an OH number of 118 mg of KO~/g and 19.1 parts of hexahydrophthalic anhydride are heated to 120C and maintA;ne~ at this temperature until an acid number of 102 mg of ROH/g is reached. Then 0.02% of chromium octoate [æic], based on the weight of the mixture of poly-THF, hexahydrophth~ acid and glycidyl ester of versatic acid and 29.7 parts of the glycidyl ester of versatic acid having an epoY;~e equivalent weight of 266 are added. The mixture is heated at 120C until the reaction product has an epQYi~e equivalent weight > 20,000, an acid number of 4 mg of XOH/g and an OH
number of 60 mg of XOH/g.
The modified polyetherdiol has an average molecular weight Mn = 1860 (calculated from the OH
number), an Mn determined by GPC of ~ 1500 and an MW/Mn = 1.67. The viscosity of an 80% strength solution in butyl acetate is 3.8 dPas (measured at 23C with a plate/cone vi~cometer).

Comparative Example 1 As described in Example 1 of Internat; ~n-1 Patent Application WO 92/04391, 0.35 mol of a commer-cially available ethoxylated trimethylolpropane having a number-average molecular weight of 1014, 0.65 mol of commercially available polyoxypropylene glycol having a number-average molecular weight of 600, 0.65 mol of the above-described modified polyetherdiol, 1.75 mol of hydroxyethyl acrylate, 0.05% of dibutyltin ~ rate (based on the total weight of the sum of components a, - 2153~1 b, c and d), 0.1% of 2,6-di-tert-butylcresol (based on the total weight of the sum of components a, b, c and d) and 30 ppm of phenothiazine (based on the total weight of the sum of components a, b, c and d) are charged to a vessel provided with stirrer, feed devices, thermal sensor and air inlet, and heated to 60C. Subsequently 2.70 mol of isophorone diisocyanate are metered in over a period of 2.5 h at 50C. The mix-ture is then diluted with phenQYyethyl acrylate to a theoretical solids [lacuna] of 90% (sum of components a to d) and the temperature is maintained at 60C until an NCO value of 1% is reached. Then 0.05% of dibutyltin ~;lAllrate and 0.51 mol of a commercially available hydroxyethyl acrylate/caprolactone oligomer having a number-average molecular weight of 344 (commercial product TONE M 100 from Union Carbide) are added at a temperature of 80C and the temperature is maintAine~
at 80C until an NCO value of < 0.1% is reAche~. The resulting oligomer has a double bond content of 0.6 mol/kg and a functionality of 2.5.
A 40% strength solution (based on the theoretical solids content) of the resulting oligomer 1 in phenoxyethyl acrylate has a viscosity of 4.9 dPas (measured at 23C with a plate/cone viscometer).
A radiation-cura~le coating composition 1 is prepared by mixing 66.8 parts of the above-described urethane oligomer 1, 29.3 parts of phenQYyethyl acrylate and 3.9 parts of ~,~-dimethyl-~-hydroxyacetophenone. Well-cleaned (above all grease-- 21S3~81 free) glass plates (width x length = 98 x 161 mm) are taped at the edge with Tesakle~ adhesive tape No.
4432 (width 19 mm) and the coating composition 1 is applied by knife coating (dry film thickness 180 ~m).
Full curing is carried out using a W irradia-tion unit fitted with two Hg medium-pressure radiators each with a lamp output of 80 W/cm, at a belt speed of 14 m/minute, in 1 pass under full-load operation.
The irradiation dose in this case is 0.15 J/cm2 (measured with the WICURE dosimeter, system EIT from Eltosch).
The results of the determination of modulus of elasticity at 0.5 and 2.5% elongation (in accordance with the stAn~rd DIN 53 455) and the results of the elongation at break test are shown in Table 3. Also shown in Table 3 are the glass transition temperature (measured using DMTA = Dynamic Mech~n;c~l Thermal Analysis) and the results of the adhesion test before and after exposure to moisture. The adhesion test in this case was carried out in accordance with DIN
StA~rd 53289.

ExamPle 1 In the vessel described in Comparative Example 1, 1.3 mol of the above-described modified polyether-diol, 1.75 mol of hydroxyethyl acrylate and 0.51 mol of a commercially available hydroxyethyl acrylate/
caprolactone oligomer having a number-average molecular weight of 344 (commercial product TONE M 100 from Union Carbide) together with 0.05% of dibutyltin A;lAllrate (based on the total weight of the sum of components a, b, c and d), 0.1% of 2,6-di-tert-butylcresol (based on the total weight of the sum of components a, b, c and d) and 50 ppm of phenothiazine (based on the total weight of the sum of components a, b, c, d) are charged and heated to 60C under a protective gas atmosphere (nitrogen/air = 3:1). Subsequently 2.70 mol of isophorone diisocyanate are metered in over a period of 2.5 h and the temperature is maintAineA at 60C until an NCO value of 1.5% is reacheA. The mixture i8 then heated to 80C and the temperature i8 main~a;n~ at 80C until an NCO value of 0.9% (theore~;~ally 0.82%) is reached. A 40% strength solution (based on the theoretical solids content) of the resulting product in phenoxyethyl acrylate has a viscosity of 3.6 dPa~
(measured at 23C with a plate/cone viscometer). Then, at a temperature of 60C~ 0. 35 mol of a commercially available propoxylated glycerol having on average 3 secondary amino groups per molecule (number-average molecular weight 5250, ~m;no equivalent weight 2220 g, content of primary amino groups ~ 0.02 mmol/g, commercial product NOVAMIN~ N60 from ConArA Chemie GmbH) are metered in at a rate such that the tempera-ture does not eY~eA 65C. The temperature is main-tained at 60C until the NCO content is < 0.1% (adjust if necessary with < 10% of the starting quantity of polyethertriamine to an NCO content of < 0.1%). The resulting oligomer has a double bond content of 0.42 mol of double bondæ/kg of oligomer and a functionality of 2.5 (average number C = C/molecule). A
40% strength solution (based on the theoretical solids content) of the resulting oligomer in phenoxyethyl acrylate has a viscosity of 4.1 dPas (measured at 23C
with a plate/cone viscometer).
In analogy to Comparative Example 1, a radiation-curable coating composition 2 is prepared by mixing 66.8 parts of the above-described urethane acrylate oligomer 2, 29.3 parts of phenoxyethyl acrylate and 3.9 parts of ~,~-dimethyl-~-hydroxyacetopheno~e.
The application and curing of the coating composition 2 is carried out in analogy to Comparative Example 1. The test results of the resulting coating are shown in Table 3.

Example 2 In analogy to Example 1, a radiation-curable oligomer 3 was prepared with the only difference being that, instead of 0.35 mol of NOVAMIN~ N 60, in this case 0.35 mol of a commercially available propoxylated glycerol having on average 3 primary amino groups per molecule were employed (Mn = 5000, amine equivalent weight 1890 g, commercial product JEFFAMIN~ T 5000 from Texaco). After the addition of the isophorone diisocyanate, in this case the temperature was main-tained at 60C until an NCO value of 1.8% was reAche~.
Subsequently the mixture was likewise heated to 80C
and the temperature was maintained at 80C until an NCO

- 215~

value of 0.9% was reached. A 40% strength solution of the resulting intermediate product has a viscosity of 2.9 dPas, measured at 23C with a plate/cone viscometer using phenoxyethyl acrylate as solvent. The reaction with the ~ine is carried out in analogy to Example 1.
A 40% strength 601ution (based on the theoretical solids content) of the resulting oligomer 3 in phenoxyethyl acrylate has a viscosity of 5.1 dPas (23C, plate/cone viscometer). The preparation, application and curing of the coating composition 3 is carried out in analogy to Example 1. The test results of the resulting coating are shown in Table 3.

Comparative ExamPle 2 In analogy to Example 1, a radiation-curable oligomer 4 was prepared with the difference being that, instead of 0.35 mol of the polyethertriamine having secondary ~;no groups (NOVANIN~ N 60), in Comparative Example 2 0.35 mol of a commercially available propoxylated glycerol having on average 3 primary ~;no groups per molecule and having a number-average molecular weight of 3000 was employed (amine equivalent weight 1060 g, commercial product JEFFAMIN~ T 3000 from Texaco). After the addition of the isophorone diiso-cyanate, in this case the temperature was maint~;ne~ at60C until an NCO value of 2.2% was reached. The mixture was then likewise heated to 80C and the tem-perature was maintained at 80C until an NCO value of 0.9% was reached. A 40% ~trength solution of the - 2153~1 resulting intermediate product of Comparative Example 2 has a viscosity of 2.7 dPas, measured at 23C with a plate/cone viscometer using phenoxyethyl acrylate as solvent. The reaction with the amine is carried out in analogy to Example 1.
A 40% strength solution (based on the theoretical solids content) of the resulting oligomer in phenoxyethyl acrylate has a viscosity of 4.6 dPas, measured at 23C with a plate/cone vi~cometer. The preparation, application and curing of the radiation-curable coating composition 4 is carried out in analogy to Example 1. The test results of the resulting coatings are shown in Table 3.

Example 3 In the vessel described in Comparative Example 1, 0.65 mol of the above-described modified polyether-diol, 0.35 mol of a commercially available, ethoxylated trimethylolpropane having a number-average molecular weight of 1000, 1.75 mol of hydroxyethyl acrylate and 0.51 mol of a commercially available hydroxyethyl acrylate/caprolactone oligomer having a number-average molecular weight of 344 (commercial product TONE M 100 from Union Carbide) together with 0.05% of dibutyltin ~ nrate (based on the total weight of components a, b, c and d), 0.1% of 2,6-di-tert-butylcresol (based on the total weight of components a, b, c and d) and 50 ppm of phenothiazine (based on the total weight of components a, b, c and d) are charged and heated to 21~3~8 1 60C under a protective gas atmosphere (nitrogen/air = 3:1). Subsequently 2.70 mol of isophorone diisocyanate are metered in over a period of 2.5 h and the temperature is maintained at 60C until an NCO value of 1.5% is reached. A 50% strength solution of the resulting intermediate product in phenoYyethyl acrylate has a viæcosity of 6.7 dPas (measured at 23C with a plate/cone viscometer). Then, at a temperature of 60C, 0.65 mol of a commercially available pLo~o~ylated glycerol having on average 2 secondary amino groups per molecule (number-average molecular weight 4150, amine equivalent weight 2350 g, content of primary amino groups < 0.02 mmol/g, commercial product NOVAMIN~ N 50 from ConA~A Chemie GmbH) are metered in at a rate such that the temperature does not eY~eeA 65C. The temperature is maintained at 60C until the NCO content is < 0.1%
(adjust if necessary with < 10% of the starting amount of polyetherdiamine to an NCO content of < 0.1%). The resulting oligomer 5 has a double bond content of 0.414 mol/kg and a functionality of 2.5. A 40% strength solution (based on the theoretical solids content) of the resulting oligomer in phenoxyethyl acrylate has a viscosity of 3.7 dPas (measured at 23C with a plate/cone viscometer).
The preparation, application and curing of the radiation-curable coating composition 5 is carried out in analogy to Example 1. The test results of the resulting coating are shown in Table 3.

`- 21535~1 ComParative Example 3 In analogy to Example 3, a radiation-curable oligomer is prepared with the only difference being that, instead of 0.65 mol of the polyetherdiamine having secondary amino groups and having a number-average molecular weight of 4150 (NOVAMIN~ N 50), in this case 0.65 mol of a commercially available poly-oxypropyle~P~i~mine having primary ~;no groups and having a number-average molecular weight of 4000 was employed (amine equivalent weight 2220 g, commercial product JEFFAMIN~ D 4000 from Texaco).
A 40% strength solution (ba~ed on the theoretical solids content) of the resulting oligomer 6 in phe~oYyethyl acrylate has a viscosity of 6.6 dPas (measured at 23C with a plate/cone viscometer). The preparation, application and curing of the coating composition is carried out in analogy to Example 1. The test results of the resulting coating are shown in Table 3.

Table 1: Composition of the oligomers in moles Example Mw Il Cl I2 C2 I3 C3eth. TMP 1000 0.35 0.35 0.35 PE-triamine 1 3000 0-35 PE-triamine 1 5000 0-35 PE-triamine 2 5250 0.35 Polyoxypropylene600 0.65 mod. PE 1860 1.30 0.65 1.30 1.30 0.65 0.65 PE-diamine 1 4000 0.65 PE-diamine 2 4150 0.65 HEA 116 1.75 1.75 1.75 1.75 1.75 1.75 ~n TONE M 100 344 0.51 0.51 0.51 0.51 0.51 0.51 IPDI 222 2.70 2.70 2.70 2.70 2.70 2.70 - 21~3~1 In Table 1 the following abbreviations were used:

eth. TMP: ethoxylated trimethylolpropane PE-triamine 1: propoxylated glycerol with primary amino groups PE-triamine 2: propoxylated glycerol with secondary amino groups mod. PE: modified polyetherdiol PE-diamine 1: polyoxypropylenedi~;ne with primary amino groups PE-diamine 2: polyoxypropylenediamine with secondary amino groups HEA: 2-hydroxyethyl acrylate TONE M 100: hydroxyethyl acrylate/caprolactone oligomer IPDI: isophorone diisocyanate N

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O _I O_I _I _ Summary of test results As is evident from comparing Examples 1 and 2 with Comparative Examples 1 and 2 and from comparing Example 3 with Comparative Example 3, the use of amino group-cont~;n;ng chain-lengthening agents having a number-average molecular weight Mn of more than 4000 results in a distinct improvement in the buffer action of the resulting coating. Thus the coatings according to the invention of Examples 1 and 2 in comparison with the coating of Comparative Bxample 2 which has an analogous structure but was prepared only using an amino group-contA;n;ng chain-lengthen;ng agent having a number-average molecular weight of only 3000, ~Yh; h; t distinctly decreased moduli of elasticity coupled with increased elongation at break and distinctly reduced glass transition temperatures, with the use of chain-lengthening agents having se~o~ry amino y~
(Example 1) bringing a further improvement in the mechanical properties of the coatings in comparison to chain-lengthening agents having primary ~;no groups (Example 2).
The comparison of Example 3 with the analogous Comparative Example 3 in which, instead of the amine according to the invention having a number-average molecular weight of 4150, in the latter case a primary ~;ne having a number-average molecular weight of 4000 was employed, also confirms the improved mech~n;c~l properties of the coatings according to the invention.

Claims

Patent claims:

1. Radiation-curable oligomers with two or more ethylenically unsaturated end groups and two or more urea and possibly urethane groups per molecule, which have been prepared from a) at least one amino- and/or hydroxy-functional com-pound with a functionality of between 3 and 4, b) at least one compound with two hydroxyl and/or amino groups per molecule, c) at least one monoethylenically unsaturated com-pound with a group having one active hydrogen atom per molecule and with a number-average molecular weight of between 116 and 1000, and d) at least one aliphatic and/or cycloaliphatic diisocyanate, components a to d having been employed in amounts such that 1.) the molar ratio of component a to component b is between 0.1:1 and 1.1:1, 2.) the molar ratio of component c to component a is between 2:1 and 10:1, and 3.) the ratio of equivalents of the isocyanate groups of component d to the amino and possibly hydroxyl groups in the sum of components a to c is between 0.9 and 1.0, characterized in that 1.) as component a at least one amino group-containing compound a1 having a number-average molecular weight of more than 4000 to 10,000 and/or at least one amino and/or hydroxyl group-containing com-pound a2 having a number-average molecular weight of from 400 to 4000 has been employed, 2.) as component b at least one amino group-containing compound b1 having a number-average molecular weight of more than 4000 to 10,000 and/or at least one amino and/or hydroxyl group-containing com-pound b2 having a number-average molecular weight of from 200 to 4000 has been employed, 3.) the oligomers have double bond contents of from 0.25 to 0.44 mol/kg, and 4.) in the preparation of the oligomers at least one amino group-containing compound a1 and/or b1 has been employed.

2. Radiation-curable oligomers according to claim 1, characterized in that the oligomers have double bond contents of from 0.3 to 0.44 mol/kg.

3. Radiation-curable oligomers according to claim 1 or 2, characterized in that as component a1 amino group-containing compounds having a number-average molecular weight of more than 4000 to 6000 and/or as component b1 amino group-containing [lacuna] of more than 4000 to 6000 have been employed.

4. Radiation-curable oligomers according to one of claims 1 to 3, characterized in that as component a2 amino and/or hydroxyl group-containing compounds having a number-average molecular weight of from 750 to 2000 and/or as component b2 amino and/or hydroxyl group-con-taining compounds having a number-average molecular weight of from 600 to 2000 and/or as component c com-pounds having a number-average molecular weight of between 116 and 400 have been employed.

5. Radiation-curable oligomers according to one of claims 1 to 4, characterized in that as component a1 and/or b1 compounds having secondary amino groups, preferably as component a1 polyalkoxylated triols having terminal, secondary amino groups and/or preferably as component b1 polyalkoxylated diols having terminal, secondary amino groups have been employed.

6. Radiation-curable oligomers according to one of claims 1 to 5, characterized in that as component a2 and/or b2 hydroxyl group-containing compounds have been employed.

7. Radiation-curable oligomers according to one of claims 1 to 6, characterized in that the molar ratio of the hydroxyl and/or amino groups of components a2 and b2 to the amino groups of components a1 and b1 is between 0 and 10, preferably between 0.1 and 3.

8. Radiation-curable oligomers according to one of claims 1 to 7, characterized in that as component a1 and/or a2 compounds having a functionality of 3 have been employed.

9. Radiation-curable oligomers according to one of claims 1 to 8, characterized in that components a to d have been employed in amounts such that 1.) the molar ratio of component a to component b is between 0.1 and 0.8, and/or 2.) the molar ratio of component c to component a is between 2.5 and 10.

10. Radiation-curable coating composition, charac-terized in that it contains at least one radiation-curable oligomer according to one of claims 1 to 9.

11. Radiation-curable coating composition according to claim 10, especially for the buffer coating of opti-cal glass fibers, characterized in that it contains A) from 10 to 78% by weight of at least one radiation-curable oligomer according to one of claims 1 to 9, B) from 0 to 60% by weight of at least one further ethylenically unsaturated oligomer, C) from 20 to 50% by weight of at least one ethyleni-cally unsaturated monomeric and/or oligomeric com-pound, D) from 2 to 8% by weight of at least one photo-initiator, and E) from 0 to 4% by weight of conventional auxiliaries and additives, the percentages by weight in each case relating to the total weight of the coating composition.

12. Radiation-curable coating composition according to claim 10, characterized in that it contains A) at least 15% by weight of at least one radiation-curable oligomer according to one of claims 1 to 9, B) from 0 to 50% by weight of at least one further ethylenically unsaturated oligomer, C) from 22 to 35% by weight of at least one ethyleni-cally unsaturated monomeric and/or oligomeric com-pound, D) from 3 to 5% by weight of at least one photo-initiator, and E) from 0.5 to 2.0% by weight of conventional auxiliaries and additives, the percentages by weight in each case relating to the total weight of the coating composition.

13. Process for coating a glass surface, especially a glass fiber, in which 1) a radiation-curable primer is applied and is cured by means of UV radiation or electron beams, and 2) a radiation-curable topcoat is applied and is cured by means of UV radiation or electron beams, characterized in that as primer and/or topcoat a radiation-curable coating composition according to one of claims 10 to 12 is employed.

14. Optical glass fiber, characterized in that it is coated with a radiation-curable coating composition according to one of claims 10 to 12.