WO1989011483A2

WO1989011483A2 - Radiation curable oligomers

Info

Publication number: WO1989011483A2
Application number: PCT/GB1989/000578
Authority: WO
Inventors: Robert Stephen Davidson; Richard John Batten
Original assignee: The Wiggins Teape Group Limited
Priority date: 1988-05-28
Filing date: 1989-05-25
Publication date: 1989-11-30
Also published as: GB8812810D0; AU3732589A; WO1989011483A3

Abstract

Modified acrylated epoxy oligomers include a group of formula (I), where R is a trialkylsilyl group or a phosphorus containing group of formula (II), where R1 and R2 are each alkyl, alkoxy, aryl, aryloxy, aralkyl or aralkoxy groups are radiation curable materials. Such modified oligomers have viscosities which make them suitable for application to substrates, particularly sheet substrates, without substantial dilution with low viscosity monomers; have good compatibility with conventional radiation curable oligomers and are curable on exposure to electron beam radiation to give cured coatings having interesting properties.

Description


  
 



   Radiation Curable Oligomers
The present invention relates to oligomers which are radiation, particularly electron beam (EB) radiation, curable, to their use in producing cured coatings on substrates and to the cured coatings produced.



  The production of EB radiation cured coatings involves coating a curable mix onto a substrate and curing it by exposure to suitable radiation thus inducing chain extension and/or cross-linking. The curable mix includes organic compounds having reactive groups that make them curable. Typically the main component is a bi- or poly-functional material (to effect cure by chain extension or, and more usually, cross-linking) having a molecular weight or average molecular weight of not more than about 1000 D. Commonly such materials are referred to in the art as 'oligomers' even though they may not fall within the strict meaning of the term. We use the term 'oligomer' herein as having the practical meaning used in the art. An important class of oligomers used in EB curable coatings is that of acrylated epoxy compounds.



  In these, the desired reactive functionality for EB curing is an ethylenic double bond and is introduced by an overall esterification reaction between an epoxy compound and acrylic acid schematically as follows:
H2C:CH.C02H
EMI1.1     
  
In order to cure the oligomer by EB radiation the oligomer will contain a significant proportion of molecules including two or more acrylate residues. In practice the oligomers used will be a mixture of compounds whose precise nature is determined by the starting materials, the degree of epoxidation and the degree of acrylation effected. An important practical property of conventional acrylated epoxy oligomers is that they have high viscosities at ambient and near ambient temperatures.



  This makes them difficult, or impossible, to coat neat onto substrates prior to curing. The viscosity of coating mixes is conventionally modified (reduced) by using so-called reactive diluents. These are typically acrylate esters of low molecular weight diols or polyols e.g. tri-propylene glycol diacrylate (TPGDA), trimethylolpropane triacrylate (TMPTA) and pentaerythritol tetra-acrylate (PETA). The use of reactive diluents is not without advantage as polyfunctional diluents such as
TMPTA and PETA can be a source of tri- and higher functionality to promote cross-linking. However, the need to use reactive diluents to lower the viscosity of mixes containing such oligomers so that it can be coated onto substrates such as paper reduces the practical usefulness of the oligomers.

  Further such oligomers are not always readily or completely miscible (compatible) with commercially available reactive diluents.



  It is known to react free hydroxyl groups in acrylated epoxy oligomers with acyl residues. Thus, the Journal of
Paint Technology for September 1971, Volume 43, Issue 560, at pages 77 to 80 describes blocking the hydroxyl groups with acryloyl groups or lower acyl e.g. acetyl, groups to reduce oligomer viscosity, and British Patent
Specifications Nos. 1197810 and   1497651    and Published PCT
Application No. WO 84/00170 describe blocking the hydroxyl   groups    with di- or poly-carboxylic acid reagents to  introduce pendent free carboxylate functionality into the oligomers to make them water dispersible, particularly for use in thermally cured paints and lacquers.

  However, such modifications tend to give materials that are not suited for direct coating onto substrates and/or are particularly susceptible to premature or spontaneous and uncontrolled polymerisation. It may be possible to prevent premature polymerisation by heavily dosing the oligomers with free radical inhibitors, but this risks the inhibition of subsequent curing by free radical mechanisms.



  The present invention is based on the discovery that reacting hydroxyl groups in acrylated epoxy oligomers to give pendent residues containing silicon or phosphorous atoms can give modified oligomers having relatively low viscosities and which are much less susceptible to premature polymerisation, even at high levels of modification, than acyl blocked oligomers of the prior art as described above. Further, the materials of the invention show excellent compatibitility with reactive monomers and can give cured coatings and films with good flexibility, toughness and adhesion.



  Accordingly, the present invention provides an oligomer, curable by electron beam radiation, including a modified acrylated epoxy function having the formula:  
EMI4.1     
 where R is an alkyl silyl group;
 or a phosphorus containing group of the formula:
EMI4.2     

 where R1 and R2 are each independently an alkyl,
 alkoxy, aryl, aryloxy, aralkyl or aralkoxy
 group.



  The invention includes a method of making a substrate, in particular a sheet substrate, having on at least one surface thereof a cured polymeric coating, which method comprises providing on the substrate a layer of a curable coating composition including at least one modified acrylated epoxy oligomer, as defined above, and curing the coating by exposing it to electron beam radiation.



  The invention further includes a method of making the modified oligomers of the invention which comprises reacting an acrylated epoxy oligomer with at least 0.25 moles of a reactive derivative of the group R (as defined above) per mole of hydroxyl group in the oligomer in the presence of a free radical inhibitor.



  The number of groups R, as defined above, included in the ol#igomer molecule depends on the number of hydroxyl groups present in the molecule of the acrylated epoxy "precursor" oligomer and the proportion replaced (directly or indirectly) by   P.    groups. As is usual with oligomers, references to the oligomer molecule are really to the "average" oligomer molecule. Generally, the modified  oligomers of the invention include at least one and usually more than one R group per oligomer molecule. As the hydroxyl functionality of many acrylated epoxy oligomers is between 1.5 and 2 this indicates a degree of modification of more than 50% and commonly it approaches 100%. However, particularly with oligomers with a higher hydroxyl functionality, lower degrees of modification may be used although they are not preferred.

  The practical lower limit appears to be about 25% modification.



  In particular, where R is an alkylsilyl group the alkyl moieties will usually be short chain typically C1 to
C6, alkyl groups e.g. methyl groups as in a trimethylsilyl group. Where R is a phosphorus-containing group, alkyl radicals in it will typically be C1 to
C10 alkyl e.g. methyl or ethyl, radicals; aryl radicals in it will typically be phenyl groups; and aralkyl radicals will typically be benzyl or phenylethyl groups. Usually, the phosphorus-containing group will be an organo-phosphate ester group or an organophosphinate ester in which the P-R1 and P-R2 bonds will both be   P-O    or P-C bonds respectively. In particular is a diaryl phosphate ester group, with the P-R1 and P-H2 bonds both   P-O    bonds.



   Typically the modified oligomers of the invention have viscosities in the range 300 to 5000 cP whereas acrylated epoxy oligomers commonly have viscosities in excess of 30000 cP.



  The modified oligomers of the invention can be cured e.g.



  by EB curing, to give tough, and usually hard, as well as flexible films e.g. as coatings on web substrates such as paper or metal. The modified oligomers will commonly be used in formulation with reactive monomers used with prior art oligomers as "reactive diluents" and the oligomers of the invention have excellent compatibitility with such reactive   monomers.    Over a wide range of proportions.  



  they can be readily formulated with reactive monomers more easily than can their unmodified acrylated epoxy "precursor" oligomer analogues, Where the group R includes a silicon atom the modified oligomer can give very flexible cured films good flexibility and can have good compatibitility with fillers, particularly silicaceous fillers.



  The modified oligomers of the invention can be made by conventional chemical synthetic reactions. Typically, the synthesis involves reacting the acrylated epoxy oligomer starting material with a reactive derivative of the modified group. Where R is a trialkylsilyl group the reactive derivative will usually be a corresponding trialkylsilyl halide, especially chloride. Where R is a phosphorus containing group, the reactive derivative can be the corresponding substituted phosphorous mono-halide especially chloride. Using halide reagents the reaction products include acid which will usually be neutralized by base e.g. a tertiary amine. As the acrylated epoxy oligomer starting material is typically a viscous liquid, the reaction will usually be performed in an inert organic solvent, e.g. an ether such as diethyl ether or tetrahydrofuran.



  Both the acrylated epoxy oligomer starting material and modified oligomer product are sensitive to free radical initiated polymerisation; it is by a free radical mechanism (radiation, especially EB, curing) that we envisage the modified oligomers will be used to make cured films. To supress uncontrolled premature polymerisation, a suitable free radical inhibitor such as an alkyl or alkoxy substituted phenol, will usually be included in the reaction mixture. In synthesising the modified oligomers of this invention we have successfuly used small quantities of such inhibitors to prevent   Dremature    polymerisation. For similar reasons the modified  oligomers of the invention will usually be stored cool e.g. below   5 C,    until just before use and/or will be dosed with inhibitors to maintain storage stability.

  By comparison, otherwise similar oligomers which have R as acyl e.g. acetyl or acrylyl, appear to be very much more susceptible to premature polymerisation to the extent that our attempts to make fully modified analogues with R as acetyl and acryloyl failed because of premature polymerisation even in the presence of an inhibitor.



  The oligomers used as starting materials in this invention include at least one and usually, on average, two or more groups of the formula:
EMI7.1     

The specific nature of the rest of the molecule is relatively less important provided that the oligomer is curable. A wide range of commercial materials can be used, typically based on polyhydroxy (including dihydroxy) compounds in particular polyphenols (including diphenols), which have been epoxidized e.g. by reacting them with epi-chlorohydrin (3-chloro-1,2-epoxypropane), and then acrylated.

  This is illustrated by the schematic reaction sequence starting from Bisphenol A, (2,2-bis(4hydroxyphenyl)propane):
EMI7.2     
  
EMI8.1     

Possible variations on this include using other bisphenols or polyphenols as the starting materials, conducting the reaction with epi-chlorohydrin to link more than one phenolic residue into the oligomer, via 1,3(2-hydroxypropylene) bridging groups, and restricting the source of acrylate groups so that the oligomer retains a proportion of epoxy groups. Acrylated epoxy oligomers of this general type are described, for example, in US Patent
Specification Nos. 3373075, 3450613 and 3959222. In order that the curing reaction can effect a substantial increase in molecular weight by chain extension and/or cross-linking, the acrylated epoxy oligomer will usually have an average acrylate functionality greater than 1 and usually greater than 1.5.



  As the acrylation reaction of the epoxy precursor introduces one hydroxyl group per acrylate group, the  hydroxyl functionality of the starting materials will be at least equal to the acrylate functionality and it may be higher if the starting material includes other hydroxyl groups.



  The main use that we see for the oligomers of the invention is in the manufacture of cured coatings on substrates. It is an advantage of the oligomers of the invention that they have viscosities that enable them to be used neat in making coatings on substrates. Of course, they can be combined with other curable materials e.g. EB curable monomers and oligomers. The enhanced compatibitility of the modified oligomers of the invention with reactive monomers enables such monomers to be used to achieve particular effects in the cured product rather than merely as viscosity diluents. The reactive monomers can be conventional reactive diluents such as TPGDA, TMPTA and PETA, referred to above, or specialised reactive monomers such as the organo-metal acrylates which are the subject of our European Patent
No. 0183764 B, e.g. methyl silicon triethoxyacrylate (MSTEA).

  The porportions of the modified oligomer and other oligomers and/or monomers will be determined by the properties desired in the cured coating.



  The coating composition may include other components such as pigments e.g. white pigments like titanium dioxide, coloured pigments, black pigments like carbon black, specality pigments such as Fe304 and dyestuffs. The proportions of these other components depends on the desired product. One important possibility is the use of no significant amount of hiding pigment so as to obtain a clear and preferably transparent and uncoloured, cured coating. This can be used as a protective layer, lacquer or varnish over the substrate so that the surface of the substrate is visible through it. This is especially  useful in the production of the visible surface of resin impregnated laminates and of furniture foils.



  The substrate used in the invention can be any substrate suitable for coating using EB curing. In particular, this invention is applicable to the coating of sheet substrates especially paper. Other substrates include plastics especially sheet and film, wood, leather, glass and metals, especially sheet metals. The major limitation on the substrate is the pratical one that it should not be unduly damaged by exposure to the EB radiation.



  The amount of coating applied to the substrate will largely be determined by the intended end use of the cured coated substrate. However, for sheet substrates the coatweight is likely to be in the range of 1 to 100 g   m'2    of coating mix prior to curing. In the manufacture of paper based products, the coatweight will vary depending on the amount of pigment used. For coatings containing little or no pigment the coatweight will typically be from 2 to 15 g   m¯2.    However if the paper substrate is printed and/or is coated to provide a part of a laminate coatweights up to 50 g   m-2    might be used. When the coating is pigmented a proportion of the coatweight is pigment.

   Where the product is intended to be paperlike, pigmented coatweights will typically be from 5 to 40 g   m-2    but for products for plastic laminates, coatweights can be higher e.g. up to 80 g   m'2.    Where the substrate is other than paper the coating can be a thin lacquer e.g. 5 to 10 g   m'2    or a thicker varnish or paint which can be up to 100 g   m-2,    for metal substrates coatweights from 30 to 80 g   m-2    can be common. Higher gross coatweights can be achieved by multiple coating steps, provided that repeated exposure to
EB radiation does not unduly damage the substrate.



  Similarly both sides of sheet substrates can be coated if  desired. Also multiple coating layers may be cured in a single pass by use of appropriate application techniques.



  Further coatings, above or below the EB cured coatings produced by the present invention, can be provided if desired and such further coatings can be provided by other techniques e.g. UV or thermal curing, solvent coating etc.



  as appropriate to the product.



  The method and equipment used to irradiate the coated substrate with EB radiation can be conventional. The EB unit can be single or multi-cathode or may use a scanning beam. Particular designs are favoured by individual equipment manufacturers and we have not observed any significant differences on rate of cure or properties of cured coatings as between the EB equipment of different manufacturers. Typically the voltage of the electron beam will be from 50 to 300kV, especially about   150kV.   



  The beam current will usually be varied so as to provide the desired dose. As is usual the EB curing zone will normally be blanketed by a gas, typically nitrogen, to exclude oxygen, which would result in a marked reduction in beam intensity and/or quenching or inhibition of the curing reaction.



  The following Examples illustrate the invention. All parts and percentages are by weight unless otherwise indicated.



  Synthesis Examples 1 to 4 describe the preparation of modified oligomers of the invention. Comparison Examples 1 and 2 describe attempts at the preparation of acyl-blocked acrylated epoxy oligomers of the prior art and illustrate the susceptibility of such materials to premature polymerisation. Application Examples 1 to 7 illustrate the manufacture of cured coated substrates  using oligomers of the invention cured by EB radiation and describe the testing of such materials, with control samples.



  NMR 1H spectra were run on a Jeol MH60 spectrometer at 60MHz using tetramethylsilane as internal standard.



  Chemical shifts are quoted conventionally as ppm from the internal standard. Hydroxyl protons were identified by chemical shift and observing disappearance of the signal after shaking the NMR sample with   D20   
Viscosities were measured at the stated temperature by:i) Reference "B"; Brookfield, spindle #4 at 100
 revolutions per minute; or ii) Reference "F-S"; Ferranti-Shirley cone and plate at
 1000 revolutions per minute; or are:iii) Manufacturers' data - as stated.



  Viscosities were measured on neat oligomers or, where the neat oligomer is too viscous to give a reliable value using the Ferrrant-Shirley instrument on a mixture of 70 parts oligomer and 30 parts 2-(butoxyethoxy)ethanol (BEE) and on various combinations of oligomer and reactive diluent (particularly TPGDA). Viscosity data are included in the test below and collected in Table 1 (below).  



   Table of Materials
Description Name or Code Source
Tripropylene glycol TPGDA Cray Valley diacrylate Products Ltd.



  Acrylated epoxy Rahn 064/MF Hans Rahn  & Co.



  oligomer Zurich
Epoxy resin Epikote 834 Shell (UK) Ltd.



  (oligomer)
Epoxy resin Araldite Ciba-Geigy Ltd.



  (oligomer) MY750
Rahn   064/MF    is a commercially available acrylated epoxy oligomeric material, which appears to be a mixture of two oligomers. It has a measured (by tetraethylammonium bromide/perchloric acid titration) residual epoxide functionality of 0.33 mol (epoxide)   kg-1    and a weight average "molecular weight" (by gel permeation chromatography) of 667D. It has an acrylate and hydroxyl functionality each of ca. 3.0 mol ()   mol¯1.    The viscosity quoted by the manufacturer is 70000 cP at 250C (method used not known but probably Brookfield).

  The measured F-S viscosity when diluted with 30% 2(2-butoxyethoxy)ethanol was 1952 cP at   24 C.    Its 1H
NMR spectrum has the following signals:  
 ppm structure assignment
 1.23 singlet 
 1.57 singlet 
 2.90 broad singlet hydroxyl protons
 3.93-4.23 broad
 5.70-6.45 complex multiplet acrylate protons
 5.57,6.70, ) multiplet 1,4-di-substituted
 6.90  & 7.03) phenyl protons
Epikote 834 is an epoxidized Bisphenol A derivative. It has a measured epoxide functionality of 4.5 mol (epoxide)   kg-1    corresponding to an average molecular weight of ca. 445D. From this it has a calculated hydroxyl functionality of 0.37 mol (OH)   mol¯1,    corresponding to the average number of 2-hydroxypropyl-bisphenol A repeat units in the molecule.

  Its 1H NMR spectrum has signals at:
 ppm structure assignment
 1.6 singlet Bisphenol A methyl
 protons
 2.55-2.90 complex multiplet epoxide ring CH2
 protons
   3#15-3.40    complex multiplet epoxide ring CH
 proton
 3.7-4.25 complex multiplet epoxide group
 methylene protons
 6.62, 6.75,) multiplet 1,4-disubstituted
 6.92  & .05) phenyl protons
Araldite   MY750    is a similar epoxy resin to Epikote 834 but  having a measured epoxy functionality of 5.3 mol (epoxide)   kg-1    corresponding to an average molecular weight of ca. 377D and giving a calculated hydroxyl functionality (2-hydroxypropyl-bisphenol A unit repeat number) of 0.13 () mol-1. Its 1H NMR spectrum is very similar to that of Epikote 834 but has slightly different proton intensities.  



   Synthesis Examples 1 to 4
 Synthesis Example 1
Silylation of acrylated epoxy oligomer
A mixture of 20 g (0.03 mol) Rahn 064/MF, 16.2 ml (11.8 g; 0.12 mol) triethylamine and 75 mg 4-methoxyphenol radical inhibitor in 400 ml dry tetrahydrofuran was stirred and cooled to below   10 C.    A solution of 15.0 ml (12.5 g; 0.12 mol) chlorotrimethylsilane in 20 ml dry tetrahydrofuran was added dropwise to the stirred oligomer solution over a period of about 30 minutes, sufficiently slowly that the temperature of the cooled reaction mix remained below   100 C.    The reaction was monitored using thin layer chromatography (tlc) on silica gel using 7:3 (by volume) ethyl acetate: petroleum ether   (60-80 C)    as eluent and iodine as developing agent, to completion after about 2 hours.

   The reaction mixture was filtered through kieselguhr in a sintered glass filter to remove solid triethylamine hydrochloride. The solid was washed with 100 nl dry ether The bulk of the solvent in the combined filtrate was removed by rotary evaporation and the remaining solution was again filtered to remove further precipitated triethylamine hydrochloride. The final traces of solvent was removed on a vacuum pump to give 21 g of trimethylsilyl modified oligomer product.



  The 1H NMR spectrum of the product has peaks at 0.2 ppm (trimethylsilyl protons) and 5.80-6.6 ppm (complex multiplet of acrylate protons). No identifiable hydroxyl proton peak was observed. The product had a measured viscosity of 1600 cP (F-S) at ca   25 C.     



   Synthesis Example 2
Silylated acrylated epoxy oligomer from Epikote 834
Synthesis of acrylated epoxy oligomer
A mixture of 27.75 ml(29.25 g; 0.405 mol) acrylic acid and 2   my(1.8    g; 0.033 mol) benzyldimethylamine in 40 ml benzene also containing 80 mg of   2 , 6-di-t-butyl-4-methylphenol    radical inhibitor, were added over a period of 30 minutes to a stirred mixture of 60 g(0.135 mol) Epikote 834 in 150 ml benzene, also containing 40 mg 2,6-di-t-butyl-4-methylphenol radical inhibitor, heated at 800C. The reaction mixture was then refluxed at   850C    for   82    hours. The progress of the reaction was monitored by tlc, as described (for the silylation reaction) in Synthesis Example 1.

  The reaction mixture was cooled to ambient temperature and a further ca. 100 ml benzene was added to ensure solution of the product. The benzene solution was washed with ice cold 0.1 M NaOH (2 x 50 ml) and the solid precipitate was filtered off. The organic phase was separated, washed with brine (50 ml), dried over anhydrous sodium sulphate and the organic solvent removed on a rotary evaporator with final traces of benzene being removed on a vacuum pump to give 64 g of acrylated epoxy oligomer as a very viscous liquid.



  The acrylated Epikote 834 had a residual measured   eposide    functionality of 1.22 mol (epoxide)   kg-1,    a calculated acrylate functionality of 1.34 mol (acrylate)   mol¯1,    a calculated hydroxyl functionality of 1.71 mol (OH)   mol¯1    and a calculated average molecular weight of ca.



  540D. The 1H NMR spectrum of this product was basically similar to that of the starting material but with the signals due to the epoxide protons much reduced,  the signal in the region 3.7 to 4.35 ppm being a complex multiplet with methylene protons, hydroxyl protons and prop-2-yl methine protons all overlapping or co-incident, and the addition of a complex multiplet at 5.55 to 6.3 ppm characteristic of acrylate protons.



  Synthesis of silylated acrylated epoxy oligomer 25 g (ca. 0.046 mol) of the acrylated Epikote 834 was silylated using chlorotrimethylsilane (9.7 ml, 8.3 g, 0.076 mol) and triethylamine (10.6 ml, 7.7 g, 0.076 mol) by the method described in Synthesis Example 1 to give 30.2 g of silylated acrylated epoxy oligomer. The 1H
NMR spectrum was substantially identical to that of the acrylated epoxy oligomer except that there was no observable signal for hydroxyl protons and there was a large signal at 0.2 ppm from the protons of trimethylsilyl groups.



   Synthesis Example 3
Silylated acrylated epoxy oligomer from Araldite MY750
Synthesis of acrylated epoxy oligomer
A mixture of 21.8 ml(23 g; 0.32 mol) acrylic acid and 1.38 ml(l g; 0.01 mol) triethylamine in 20 ml benzene containing 80 mg of 2,6-di-t-butyl-4-methylphenol radical inhibitor, were added over a period of 30 minutes to a stirred mixture of 60 g(0.16 mol) Araldite   MY750    in 150 ml benzene, also containing 40 mg of 2,6-di-t-butyl-4-methylphenol radical inhibitor, heated at   800 C.    The reaction mixture was ref fluxed at   850C    for 6 hours and the progress of the reaction was monitored by tlc as in Synthesis Example 2. The mixture was cooled to ambient temperature and washed with ice cold 0.1 M NaOH (2 x 75 ml).

  The emulsion formed in this washing was broken  by filtering it through a sintered glass filter. The organic phase was further washed with brine (2 x 75 ml), dried over anhydrous sodium sulphate and the organic solvent removed on a rotary evaporator with final traces of benzene being removed on a vacuum pump to give 72.9 g of acrylated epoxy oligomer as a very viscous liquid.



  The 1H NMR spectrum was very similar to that of the acrylated epoxy oligomer made from Epikote 834 and showed much reduced epoxide protons, the presence of hydroxyl protons and the characteristic acrylate proton complex multiplet. The product had a residual measured epoxy functionality of 0.59 mol (epoxide)   kg-1,    a calculated acrylate functionality of 1.7 mol (acrylate)   mol¯1,    a calculated hydroxyl functionality of 1.83 mol (OH)   mol¯1    and a calculated average molecular weight of ca.



  500D.



  Synthesis of silylated acrylated epoxy oligomer
The acrylated Araldite MY750 was silylated by the general method described in Synthesis Example 2 but using 20 g (ca. 0.04 mol) acrylated MY750, 10.7 m1(7.75 g; 0.077 mol)triethylamine and 9.7 ml(8.3 g; 0.07 mol) chlorotrimethylsilane, to give 21.25 g of silylated acrylated epoxy oligomer.



  The 1H NMR spectrum of this product corresponded to that of the acrylated epoxy oligomer but lacked any hydroxyl proton signal and had a large signal at 0.15 ppm from the trimethylsilyl protons. Qualitatively, it was very similar to that of the silylated acrylated epoxy oligomer of Synthesis Example 2.  



   Synthesis Example 4
Phosphorylation of acrylated epoxy oligomer
A stirred mixture of 30 g (0.045 mol) Rahn 064/MF in 250 ml dry tetrahydrofuran, 24.3 ml (17.6 g; 0.177 mol) triethylamine and ca. 70 mg 4-methoxyphenol was cooled to between 0 and   50C    and 36.7 ml (47.6 g; 0.177 mol) diphenyl chlorophosphate (the mono acyl chloride of phosphoric acid diphenyl ester) in 25 ml dry tetrahydrofuran was added dropwise over 30 minutes. During the addition the reaction temperature was not allowed to rise above about   15 C.    Thereafter the reaction mixiture was stirred at   250C    for 16 hours and at   400C    for 1 hour. The reaction was monitored by tlc, on silica gel using 7:3 (by volume) ethylacetate:hexane as eluent and iodine as developing agent.

   The reaction mixture was cooled to ca.   0 C    on an ice bath and 100 ml ice water and 300 ml diethyl ether were added, the mixture was stirred and then the aqueous and organic layers separated. The organic layer was washed with ice cold 0.1 M aqueous HC1 (2 x 75 ml), ice cold 0.1 M aqueous NaOH (2 x 75 ml) and saturated aqueous
NaCl solution   t2    x 75 ml), dried over anhydrous sodium sulphate and the solvent removed on a rotary evaporator with the final traces being removed on a vaccum pump at 35 to 400C to give 52.3 g (0.039 mol;   86.9s    theory) of the product as a pale yellow liquid.



  The 1H NMR spectrum of the product was very similar to that of Rahn 064/MF but having no hydroxyl proton signal (no change after D20 shake) and a large signal (broad singlet) at 7.20 ppm assigned to the protons of the phenyl groups.  



   Comparison Synthesis Examples 1 and 2
 Comparison Synthesis Example 1
Acetylation of acrylated epoxy oligomer 53.7 g (0.081 mol) Rahn 064/MF, 44 ml (32g; 0.32 mol) triethylamine and 100 mg 4-methoxyphenol radical inhibitor were stirred in 650 ml dry tetrahydrofuran and cooled to below   10 C.    A solution of 22.4 ml (24.8 g; 0.32 mol) acetyl chloride in 80 ml dry tetrahydrofuran was added over a period of 45 minutes, sufficiently slowly that the temperature of the cooled reaction mix remained below 100C. The progress of the reaction was monitored by tlc, as described in Synthesis Example 1, to completion after about 2 hours. The reaction mixture was filtered through kieselguhr in a sintered glass filter and the solid triethylamine hydrochloride retained was washed with 350 ml dry ether.

  The combined filtrates were washed successively with ice cold 0.1 M aqueous HCl (2 x 50 ml), ice-cold 0.1 M aqueous NaOH (2 x 50 ml) and brine (100 ml). The organic phase was dried over anhydrous sodium sulphate and then the solvent was removed on a rotary evaporator with final traces being removed on a vacuum pump. Although the synthetic reaction appeared to run satisfactorily, it was found that the product isolated from the reaction mixture had undergone spontaneous polymerisation.  



   Comparison Synthesis Example 2
Acrylation of acrylated epoxy oligomer
The general method described in Comparison Synthesis
Example 1 was used but using the following quantities of reagents (quantities of other materials being scaled accordingly):
Rahn 064/MF 40.35 g; 0.06 mol triethylamine 33.2 ml; 24 g; 0.24 mol acryloyl chloride 19.2 ml; 21.6 g; 0.24 mol
Although the synthetic reaction appeared to run satisfactorily, the product recovered after work up, as described in Comparison Synthesis Example 1 had undergone spontaneous polymerisation.



  Application Examples
In the Application Examples below various formulations of oligomer and TPGDA as reactive monomer (reactive diluent for control formulations), as set out in Table 2 below, were made up, coated onto sheet substrates and cured by irradiation with EB. The coatings were cured using an
ESH 150 scanning electron beam unit, made by Otto   Purr,    operating at   150#kV.    Doses of EB radiation quoted are of the output of the EB unit i.e. they refer to applied dose rather than specifially to the absorbed dose.

  In
Application Examples 1 to 7 the respective formulations were applied to a paper web substrate (70 - 75   gum¯2   
Gateway Natural Tracing made by Wiggins Teape) using a syringe and passing the web under a forward rotating chrome smoothing roll at 10 m   mien¯1.    The coated web was then passed through the   EB    unit to cure the coatings.  



  The coatweights, applied doses and testing results on these samples are set out in Table 3 below. In
Application Example 8, the coating formulation was applied as described above, onto sheets of aluminium foil stuck to the paper web using adhesive tape and the coating was then
EB cured. The coatweights, applied dose and results of testing (by the methods described below) are included in
Table 3 below.



  From the results quoted in Table 3 it can be seen that the coatings including modified oligomers of the invention give coatings which are more flexible than the controls, retain good i.e. low, brittleness.



  All the modified oligomers of the invention were more readily incorporated into formulations with reactive diluents than the unmodified (precursor) oligomers.



  Test Methods:
Pencil Hardness - A pencil with changeable 0.5mm flat ended leads (made by Rotring) was held vertical with the lead in contact with the surface of a cured resin coating on a substrate placed on a flat, horizontal surface. The paper was gently pulled along under the lead. The pencil hardness is the hardness of the pencil lead (expressed in pencil hardness i.e. H, 2H, 3H, 4H, 4H) required to break the surface of the coating.



  Cross Hatch - diagonal cross hatch lines were cut at 2mm intervals using a scalpel into the surface of a cured resin coating on a substrate. The amount of coating debris in the cut grooves, especially at points of intersection, is noted. The more debris the poorer the combination of brittleness and adhesion. The results are expressed on a ranking scale from 0 (best) to 5 (worst).  



  Brittleness - A strip of substrate coated with a cured layer of resin was folded in half and the crease examined to see to what extent the coating had fractured. (A spot of dye solution can be used to aid this determination.)
The samples were ranked on a scale of increasing brittleness from 0 (not brittle - coating not showing fracture) to 5 (very brittle).  



   Table 1
Viscosity
EMI25.1     


<tb>  <SEP> Material <SEP> Neat <SEP> BEE <SEP> TPGDA
<tb>  <SEP> 30% <SEP>    25 <SEP>     <SEP>    40 <SEP>     <SEP>    60 <SEP>     <SEP> 75
<tb> Rahn <SEP> 064/MF <SEP> 70000* <SEP> 1952 <SEP> 4150 <SEP>    - <SEP>     <SEP> 193 <SEP>     <SEP> - <SEP>    
<tb>  <SEP> (B)
<tb> SE1 <SEP> 1600 <SEP> - <SEP> 241 <SEP> 43 <SEP> - <SEP> - <SEP> 
<tb> Acrylated <SEP> Epikote <SEP> - <SEP> - <SEP> - <SEP> - <SEP> - <SEP> 22
<tb> 834 <SEP> (See <SEP> SE2)
<tb> SE2 <SEP> - <SEP> - <SEP> - <SEP> - <SEP> - <SEP> 16
<tb> Acrylated <SEP> Araldite <SEP> - <SEP> - <SEP> 329 <SEP> - <SEP> 28 <SEP> - <SEP> 
<tb> MY570 <SEP> (See <SEP> SE3)
<tb>   SE3 <SEP>     <SEP> - <SEP> - <SEP> 53 <SEP> - <SEP> 11 <SEP> - <SEP> 
<tb> SE4 <SEP> - <SEP> 

   212 <SEP> - <SEP> - <SEP> 130 <SEP> - <SEP> 
<tb> 
Footnote to Table
 (B) indicates Brookfield viscosity
 * indicates manufacturer's data (probably Brookfield)
 BEE = 2-(2-butoxyethoxy)ethanol i.e.



   CH3.CH2.CH2.CH2.O.CH2.CH2.O.CH2.CH2.OH  
Table 2 - Formulations
EMI26.1     


<tb> No. <SEP> Oligomer <SEP> wt.% <SEP> ratio <SEP> Notes
<tb>  <SEP> Oligomer:
<tb>  <SEP> TPGDA
<tb>   AE1 <SEP>     <SEP> Example <SEP> 1 <SEP> 100:0 <SEP> neat <SEP> oligomer
<tb> AE2 <SEP> Example <SEP> 1 <SEP> 60:40
<tb>  <SEP> C2 <SEP> Rahn <SEP>    064/MF <SEP>     <SEP> 60:40
<tb> AE3 <SEP> Example <SEP> 1 <SEP> 40:60
<tb>  <SEP> C3 <SEP> Rahn <SEP> 064/MF <SEP> 40:60
<tb> AE4 <SEP> Example <SEP> 2 <SEP> 75:25
<tb>  <SEP> C4 <SEP> Acr. <SEP> 750 <SEP> 75:25 <SEP> Acrylated <SEP> Araldite <SEP> MY750
<tb>  <SEP> See <SEP> Example <SEP> 2
<tb>   AES <SEP>     <SEP> Example <SEP> 3 <SEP> 40:60
<tb>  <SEP>    C5 <SEP>     <SEP> Acr.

   <SEP> 750 <SEP> 40:60 <SEP> Acrylated <SEP> Araldite <SEP> MY750
<tb>  <SEP> See <SEP> Example <SEP> 3
<tb> AE6 <SEP> Example <SEP> 3 <SEP> 25:75
<tb>  <SEP> C6 <SEP> Acr. <SEP> 834 <SEP> 25:75 <SEP> Acrylated <SEP> Epikote <SEP> 834
<tb>  <SEP> See <SEP> Example <SEP> 3
<tb> AE7 <SEP> Example <SEP> 4 <SEP> 60:40
<tb>  <SEP> C7 <SEP>    i <SEP>     <SEP> Rahn <SEP> 064/MF <SEP> 60:40 <SEP> Same <SEP> formulation <SEP> as <SEP> C2
<tb> AE8 <SEP> Example <SEP> 4 <SEP> 60:40
<tb>  <SEP> C8 <SEP> Rahn <SEP> 064/MF <SEP> 60:40 <SEP> Same <SEP> formulation <SEP> as <SEP> C2
<tb>   
Table 3
EMI27.1     


<tb>  <SEP> Ct.wt. <SEP> Dose <SEP> Pencil <SEP> Cross <SEP> Brittleness
<tb> No.

  <SEP> (gm-2) <SEP>    (kGy) <SEP>     <SEP> Hardness <SEP> Hatch
<tb>   E2 <SEP>     <SEP> 14 <SEP> 5 <SEP> 2B <SEP> 1/2 <SEP> 1
<tb>  <SEP> 15 <SEP> 20 <SEP> 2H/3H <SEP> 1 <SEP> 1
<tb>   AE2 <SEP>     <SEP> 20 <SEP> 5 <SEP> HB <SEP>    - <SEP>     <SEP> 1
<tb>  <SEP> 22 <SEP> 20 <SEP> 4H <SEP>    - <SEP>     <SEP> 1/2
<tb> C2 <SEP> 25 <SEP> 5 <SEP> 4H <SEP> 2/3 <SEP> 3
<tb>  <SEP> 8 <SEP> 20 <SEP> 4H <SEP> 1/2 <SEP> 1/2
<tb> AE3 <SEP> 23 <SEP> 5 <SEP> H <SEP> 1 <SEP> 1/2
<tb>  <SEP> 24 <SEP> 20 <SEP> 4H <SEP> 1 <SEP> 1/2
<tb> C3 <SEP> 7 <SEP> 5 <SEP> 4H <SEP> 1 <SEP> 1
<tb>  <SEP> 7 <SEP> 20 <SEP> 4H <SEP> 1/2 <SEP> 1/2
<tb> AE4 <SEP> 17 <SEP> 5 <SEP> 3H <SEP> 1/2 <SEP> 1
<tb>  <SEP> 18 <SEP> 20 <SEP> H <SEP> 2/3 <SEP> 1
<tb> C4 <SEP> 35 <SEP> 5 <SEP> 4H <SEP> 1/2 <SEP> 1
<tb>  

   <SEP> 26 <SEP> 20 <SEP> 4H <SEP> 1 <SEP> 1
<tb>   AES <SEP>     <SEP> 23 <SEP> 5 <SEP> 4H <SEP> 1 <SEP> 1
<tb>  <SEP> 28 <SEP> 20 <SEP> 4H <SEP> 1/2 <SEP> 1
<tb>   C5 <SEP>     <SEP> 24 <SEP> 5 <SEP> 4H <SEP> 1 <SEP> 1
<tb>  <SEP> 24 <SEP> 20 <SEP> 4H <SEP> 2 <SEP> 2
<tb> AE6 <SEP> 26 <SEP> 5 <SEP> 4H <SEP> 1 <SEP> 1
<tb>  <SEP> 25 <SEP> 20 <SEP> 4H <SEP> 1/2 <SEP> 2
<tb> C6 <SEP> 30 <SEP> 5 <SEP> 4H <SEP> 1 <SEP> 1/2
<tb>  <SEP> 28 <SEP> 20 <SEP> 4H <SEP> 2/3 <SEP> 1/2
<tb> AE7 <SEP> 10 <SEP> 5 <SEP> 4H <SEP> 1 <SEP> 1/2
<tb>  <SEP> 31 <SEP> 20 <SEP> 4H <SEP> 1 <SEP> 1/2
<tb> C7 <SEP> 25 <SEP> 5 <SEP> 4H <SEP> 2/3 <SEP> 3
<tb>  <SEP> 8 <SEP> 20 <SEP> 4H <SEP> 1/2 <SEP> 1/2
<tb> AE8 <SEP> 10 <SEP> 5 <SEP> 4H <SEP> 1 <SEP> 1/2
<tb>  <SEP> 31 <SEP> 20 <SEP> 4H <SEP> 1 <SEP> 1/2
<tb> C8 <SEP> 25 <SEP> 5 <SEP> 4H <SEP> 2/3 <SEP> 3
<tb>  <SEP> 8 

   <SEP> 20 <SEP> 4H <SEP> 1/2 <SEP> 1/2
<tb>

Claims

Claims 1. An oligomer, curable by electron beam radiation, including a modified acrylated epoxy function having the formula: EMI28.1 where R is an alkyl silyl group; or a phosphorus containing group of the formula: EMI28.2 where R1 and R2 are each independently an alkyl, alkoxy, aryl, aryloxy, aralkyl or aralkoxy group.

2. An oligomer as claimed in claim 1 in which there is an average of more than one modified acrylate epoxy function of the formula (I) per molecule.

3. An oligomer as claimed in claim 2 having a degree of modification of at least 50.

4. An oligomer as claimed in claim 1 having a viscosity of from 300 to D000 cP.

5. An oligomer as claimed in claim 1 wherein R is an alkylsilyl group in which the alkyl groups are C1 to C6 alkyl groups.

6. An oligomer as claimed in claim 1 wherein R is a phosphorus containing group of the formula EMI28.3 in which R1 and R2 are each independently a C1 to C10 alkyl or alkoxy group or a phenyl, phenoxy, benzyl, benzyloxy, phenethyl or phenethyloxy group.

7. An oligomer as claimed in claim 1 wherein R is a diaryl phosphate ester group.

8. A method of making a modified oligomer as claimed in claim 1 which comprises reacting an acrylated epoxy oligomer with at least 0.25 moles of a reactive derivative of the group R (as defined in claim 1) per mole of hydroxyl group in the oligomer in the presence of a free radical inhibitor.

9. A method as claimed in claim 8 in which where R is a tri-alkyl silyl group, the reactive derivative is a corresponding trialkyl silyl halide, and where R is a phosphorus containing group the reactive derivative is a corresponding substituted posphorus mono-halide.

10. A method of making a substrate, in particular a sheet substrate, having on at least one surface thereof a cured polymer coating, which method comprises provided on the substrate a layer of a curable coating composition including at least one modified acrylated epoxy oligomer, as claimed in claim 1, and curing the coating by exposing it to electron beam radiation.

11. A method as claimed in claim 10 wherein the curable coating composition additionally includes one or more other curable monomer and/or oligomer.

12. A substrate, in particular a sheet substrate, having on at least one surface thereof a cured polymeric coating including units, within the polymer of the coating, derived from at least one modified acrylated epoxy oligomer as claimed in claim 1.