GB2104086A - Polymerizable unsaturated polyurethanes - Google Patents

Abstract

A polymerizable unsaturated polyurethane of the formula: <IMAGE> in which E represents an ethylenically unsaturated, free radical polymerizable group, D represents the residue of a polyisocyanate having at least two of its isocyanate groups reacted to form <IMAGE> groups bonded to E and R, R represents the residue of a polyether polyol, polylactone polyol, poly(acrylate) polyol, polysiloxane polyol or poly(glycidyl ether) polyol having at least a+b hydroxyl groups, the residue formed by removal of hydrogen from the hydroxyl groups, the polyol having a number average molecular weight between 90 and 10,000, and a hydroxy equivalent weight of from 45 to 5,000, A represents a carboxylic acid containing group, a is a number having an average value between 2 and 20, and b is a number having an average value between 0.3 and 10.

Description

1 GB 2 104 086 A 1.

SPECIFICATION Polymerizable unsaturated polyurethanes

This invention relates to polymerizable unsaturated polyurethanes which are particularly suitable for use in the photopolymerizable compositions, photoirnagable recording element and process for imaging with photopolymerizable compositions disclosed in our copending British Patent Application 5 No. 7914903 (Serial No. 2020297).

Photopolymerizable compositions have been used in photosensitive elements, such as printing plates, for a number of years. Such compositions have been satisfactory only where contact printing of the plate and relatively long time exposures can be tolerated. Most representative of the prior art are compositions disclosed in U.S. Patents Nos. 3,218,167 and 3,887,450. In U. S. Patent No. 3,218,167 10 photosensitive compositions comprising 1) an ethylenically unsaturated compound (e.g., pentaerythritol polyacrylate), 2) a sensitizing dye, and (3) a thermoplastic binder (e.g., cellulose ether or polyvinyl ether). In U.S. Patent No. 3,887,450 a radiation sensitive composition is described which comprises 1) an acrylic monomer (e.g. pentaerythritol triacrylate), 2) a photosensitive dye, and 3) a binder comprising a copolymer of styrene and a carboxyl containing comonomer (e.g., acrylic or maleic 15 acid). This latter composition has the advantage of being developable (i. e. soluble in non-irradiated areas) by basic developers. The composition is relatively slow, however, and must be exposed in the absence of oxygen.

Radiation sensitive elements which are oxygen insensitive have been produced by overcoating the elements with an oxygen barrier layer as in U.S. Patent No. 3,895,949. Here a support bearing a 20 photopolymerizable composition comprising a glycidyl acrylate adduct of a styrene/maleic anhydride adduct, and ethylenically unsaturated monomer (e.g., pentaerythritol tetraacrylate), and a photoinitiator is overcoated with an oxygen/moisture barrier layer (e.g., a copolymer of an acrylic acid and copolymerizable ethylenically unsaturated compound). Such elements are relatively oxygen insensitive (by reason of the barrier layer), and with proper selection of the barrier layer can be developed with basic solutions after exposure. These elements remain relatively slow and require the additional coating operation to provide the barrier layer. In addition to the time and cost factors resulting from the overcoating operation, careful control of solvents and conditions in this step must be observed to avoid sensitometric damage to the photosensitive layers.

Other radiation sensitive compositions known in the art include those of U.S. Patent No. 30 3,827,956. This ultraviolet radiation sensitive composition comprises 1) an acrylic monomer (e.g., pentaerythritol triacrylate), 2) an acrylate oligomer (e.g., the reaction product of toluene diisocyanate with two equivalents of 2-hydroxyethyl methacrylate), and 3) a halogenated polynuclear lactone catalyst. U.S. Patents Nos. 3,297,745; 4,017,649; and 4,065,627 describe other acrylate end-capped urethane oUgomers which can be homopolymerized or copolymerized with other ethylenically unsaturated compounds. These materials are photopolymerizable with relatively high radiation sensitivity and low oxygen sensitivity, but they are not base soluble and have no base developable printing plate capability because of this. These compositions also have poor bonding characteristics to metal surfaces such as zinc and aluminum.

Our copending British Patent Application No. 7914903 (Serial No. 2020297) discloses a 40 photopolymerizable composition comprising:

1) 10 to 60 parts by weight of an organic film forming a polymer binder, 2) 10 to 60 parts by weight of a free radical polymerizable monomer having at least one ethylenically unsaturated group, 3) 0.1 to 12 parts by weight of a photoinitiator system capable of initiating free radical polymerization upon absorption of electromagnetic radiation, and 4) 10 to 60 parts by weight of an unsaturated polyurethane of the formula:

0 li (E-D-hR--ukl-A)b in which 50 E represents an ethylenically unsaturated, free radical polymerizable group, D represents the residue of a polyisocyanate having at least two of its isocyanate groups reacted to form -NHC 11 U groups bonded to E and R, R represents the residue of a polyol having at least (a+b) hydroxyl groups, the residue being 55 formed by removal of hydrogen from the hydroxyl groups, the polyol having a number average molecular weight between 90 and 10,000 and a hydroxy equivalent weight of from 45 to 5000, 2 A represents a carboxylic acid containing group, a is a number having an average value between 2 and 20, and b is a number having an average value between 0.3 and 10, GB 2 104 086 A 2.

the components 1) to 4) totalling 100 parts by weight.

It has been found that high speed radiation sensitive photopolymerizable compositions with 5 excellent adhesion to certain substrates, especially aluminum surfaces, which compositions are suitable for use in radiation sensitive printing plates and colour proofing sheets can be made according to that invention. Such compositions also can have extensive shelf stability and oxygen insensitivity, and the polymers produced therefrom are tough and have a long service life. The compositions are also base soluble and can be developed in basic solutions in printing plate processes.

A storage stable photosensitive imaging element of particular use in providing base developable printing plates can be made by applying the photosensitive compositions of that invention to a support layer.

Photosensitive compositions in accordance with that invention have unexpectedly high radiation sensitivity and no oxygen or moisture sensitivity.

It is preferred to have as the photoinitiator system, a photosensitizer and a compound which when photosensitized is capable of initiating free radical polymerization. In the practice of that invention the second compound is defined as an initiator. The photoinitiator system is more preferably present in an amount of 0.5 to 10 parts. Preferably, the photosensitive composition comprises per 100 parts total:

to 45 parts by weight of polyurethane, to 35 parts by weight of binder, to 50 parts by weight of monomer, 0.2 to 10 parts by weight of initiator (more preferably 2 to 8), 0.1 to 5 parts by weight of photosensitizer (more preferably 1 to 4).

Most preferably the compositions of the present invention comprise per 100 parts total by weight:

f A 20 to 35 parts polyurethane, to 30 parts binder, to 50 parts monomer, 2 to 6 parts initiator, and 1 to 3 parts photosensitizer.

Generally, the photosensitive compositions of that invention are prepared by mixing the components in a low boiling (at atmospheric pressure boiling at less than about 1 50IC) polar solvent that is not reactive with the carboxyl groups or ethylenically unsaturated groups of the components, 35 such as methanol, ethanol, propanol, acetone, methylethyl ketone, tetrahydrofurane or mixtures thereof. There may even be water present although less than 50% by weight of water in the solvent is preferred. The amount of solvent used (generally 0 to 98% by weight, preferably 10 to 96% by weight and in lithographic applications 85 to 95% by weight solvent is most preferred) depends upon the desired viscosity and desired coating thickness. It is often desirable to add a surfactant or coating aid, 40 but these aids, including the solvent are not functionally required for practice of the invention, but are merely better modes of practice. 0.00 1 to 2% of surfactant, particularly silicone or fluorcarbon surfactants will usually be sufficient.

These compositions may contain any number of additional useful additives such as dyes, pigments, coating aids, surfactants, etc.

The coating weight of the compositions of the present invention is usually 0.3 to 9 g/m', preferably 0.5 to 5 g/m', and most preferably 0.8 to 2.4 g/M2. Suitable substrates include resin coated paper, various transparent or opaque plastics sheet or film, metal sheets and foils (preferably aluminum substrates that have been grained and anodized). The coated substrates must be maintained in the absence of light unless the element is sensitized to a narrow range of the electromagnetic spectrum 50 outside the range of normal light and the element is provided with a filter layer which excludes normal visible light.

The preferred utility of the photopolymerizable compositions of that invention is as a presensitized plate for use in printing operations such as in the formation of lithographic plates. This structure comprises a grained and anodized aluminum substrate coated with from 0.3 to 9 g/M2 of the 55 compositions of the present invention. Grained substrates are surfaces which have been textured or roughened. This treatment is well known in the art and can be effected by brush graining (roughening with an abrasive material), chemical etching, or electrochemical graining. Anodizing is the well known anodic oxidation of metal surfaces. Polymer top coat layers used in these constructions must be dissolvable in aqueous alkaline solutions of pH 8-13 such as the aqueous developers of the examples. 60 A generic structural formula for the urethane oligomers can be drawn as follows:

0 H W-D-hIR-+OCA), 3 GB 2 104 086 A 3 wherein E is an ethylenically unsaturated, free radical polymerizable group, preferably selected from acryloyloxyalkoxy (alternatively named acryloxyaikoxy), methacryloyloxyalkoxy (alternatively named methacryloxyalkoxy), vinylaikoxy, and allyloxy, 5 D is the residue of polyisocyanate (preferably a diisocyanate) having at least two of its - N=C=0 5 groups reacted to form groups, D bonding E to R, A is a carboxylic acid containing group, (e.g., 11 U 0 --(-CH,),,,C 10 OH 0 H -C,H4k'Uri, etc.), a is a number having an average value between 2 and 20, b is a number having an average value between 0.3 and 10, and m=1 to 6, R is the residue of a polyol having at least a+b hydroxyl groups and a number average molecular15 weight between 90 and 10,000 and a hydroxyl equivalent of from 45 to 5000, the residue formed by removal of hydrogen from the hydroxyl groups.

The backbone of the oligomer, group R, may be any aromatic or aliphatic polyol having a molecular weight between 90 and 10,000. The backbone of the oligomer may be any oligomer with the requisite molecular weight and number of hydroxyl groups, but polyesterpolyols and polyoxyalkylene polyols are preferred. Linear oligomeric polyols are useful but the branched or three dimensional polyols such as polycaprolactone polyols are preferred. The backbone may be prepared by any of the many well known methods of forming polyhydroxyl substituted oligomers having a molecular weight between 90 and 10,000. The polyols must have a hydroxy equivalent weight of between 45 and 5,000 to be useful according to the present invention. Preferably the polyol has a 25 hydroxy equivalent weight between 90 and 4,000 and most preferably between 200 and 2,000.

The oligomeric backbone may be homopolymeric, copolymeric, graft polymeric, or mixtures thereof. For example, polycaprolactone polyols may be used, or lower molecular weight polycaprolactone polyols (average molecular weights of less than, for example, 500) may be joined by polyacids (preferably dicarboxylic acids) or by polyisocyanates (preferably dlisocyanates) to form higher 30 molecular weight oligomer backbones.

In the synthesis of the oligomers useful in that invention, it is preferred to join the E-D substituent to the oligomeric backbone R by first separately forming an adduct of the polylsocyanate of which D is a residue by reacting one mole of the dilsocyanate with one mole of an ethylenically unsaturated free radical polymerizable monomer having one hydroxyl group. The adduct formed is then 35 reacted with a hydroxyl group on the oligomer polyol backbone (the reaction being with an isocyanate group). In an alternative method where the compound with the free radical polymerizable group with one hydroxyl group and the polyisocyanate are added to the oligomeric polyhydroxy backbone before forming the E-D adduct, the polyisocyanate will act both as a polymer extender for the ollgomer and as an adduct former with the free radical containing compound. In such a reaction there would be far 40 less control over the final product and there would be a tendency for the oligomer to gel. Therefore the free radical polymerizable monomer and the polyisocyanate (preferably diisocyanate) in an independently run synthesis form, for example, an isocyanatoalkylacrylate, isocyanatoalkyimethacrylate, an isocyanato alkyl ether, or isocyanatoalkylvinyl ether adduct. 45 The adduct (E-D) formed in that step is then caused to react with the polyhydroxy containing 45 backbone so that the remaining isocyanate group of the adduct reacts with some, but not all, of the hydroxyl groups on the oligomer to bond thereto. The carboxylic acid groups are added to the oligomeric backbone preferably after addition of the free radical polymerizable moieties by reaction of remaining hydroxyl groups on the oligomeric backbone with a compound having free carboxyl groups. Preferably such a compound is a dicarboxylic 50 acid or anhydride so that the linking bond to the oligomeric backbone is an ester group. An isocyanate linkage can be formed by first making an acid-isocyanate adduct.

4 GB 2 104 086 A 4 A more specific formula representing preferred oligomeric materials is as follows:

0 0 wherein D, a, and b are as defined above, 5 E represents or where 0 11 -4-CH,-4iO-C-C=CH,, 1 MI ---CH2--n-O--C=CH2, 1 h- -(-CH,-+nO-CH,-CH=CH,, R' is -H or -CH, and n is an interger of from 2 to 4 inclusive, R' is the residue formed by the removal of active hydrogen atoms and hydroxyl groups from oligomeric Whydroxy carboxylic acids or the residue formed by the removal of active hydrogen atoms 15 and hydroxyl groups from oligomeric diols, R' is a residue, having a valence of a plus b, of an afiphatic polyol having the formula R 5( OH)a+b after removal of a+b hydrogens from hydroxyl groups, or a polyol having the formula (HO) R 5_0-D-O-Rs(OH) 2 a+b-1 2 after removal of a+b-1 hydrogens from hydroxyl groups wherein R5 is the residue of an aliphatic polyol radical formed by having the OH groups removed therefrom and having 3 to 10 valences substituted 20 with OH groups and which can have one or two ether oxygen atoms in the aliphatic backbone, and R 3 is the residue of a dicarboxylic acid having both 0 1 -C-OFI groups removed therefrom. 25 Preferably the molecular weight of (R'-+a-R 2 (R1)b is between 200 and 5,000. Particularly desirable aliphatic polyols from which R 2 is formed are polyether polyols, polyester polyols, polyfactone polyols, polyolefin polyols, polydiene polyols, polysiloxane polyols, poly (alkylacrylate) polyols, and poly (glycidyl ether) polyols. A particularly desirable material is represented by the structural formula 0 0 11 11 wherein 0 0 p R' and R' are as defined above, c is 2 to 5 inclusive, p is a number average value of 2 to 7.7, q is a number average value of 0.3 to 4, R' is the residue of a diisocyanate having two -N=C=0 groups removed therefrom and preferably is an aromatic residue thereof, and R is an organic polyol radical which is the residue of an organic polyol with at least three hydroxyl groups removed therefrom and having a molecular weight of from 90 to 10,000, preferably 40 selected from aliphatic triols, tetrols and pentols, poly(oxyalkylene)triols, tetrols and pentols, GB 2 104 086 A 5 polyestertriols, tetrols and pentols, polyactonetriols, tetrols and pentols, polyolefintriols, tetrols and pentols, polyacrylatetriols, tetrois and pentols, polyalkylacrylatetriols, tetrols and pentols, and polysiloxanetriols, tetrols and pentols.

Another particularly desirable material can be represented by 0- wherein 0 9 NW (CH 2)d 0- - 010 1].

0 0 0 1 c 0EgkC"2)do!LII-RS-OH 0 CHI-)-do-ICNHR6NUCOlf OCC- h-f 11 CHIt CH 0 4 1 _ 1 2 R' and R' are defined above, d is 1 to 6 inclusive, e is an average value of 0.5 to 5 inclusive, f is an average value of 1 to 6 inclusive, R' is hydrogen or methyl, R' is the residue of an organic polyisocyanate (preferably diisocyanate) with two isocyanate groups removed therefrom, R' is an alkanepolyyl radical having a valence of h+ 1 that is the residue of an alkenpolyof having h+ 1 hydroxyl groups removed therefrom (preferably having h+ 1 hydroxyl groups before removal), said 15 alkanepolyol having a molecular weight of from 100 to less than 10,000 and preferably 200 to 2,000, wherein h is an integer of from 2 to 8.

Certain of the unsaturated polyurethanes described above are new. Therefore according to the present invention there is provided a polymerizable unsaturated polyurethane of the formula:

0 11 (E-D)arIkUkl-APb in which to form groups bonded to E and R, R represents an ethylenically unsaturated, free radical polymerizable group, D represents the residue of a polylsocyanate having at least two of its isocyanate groups reacted -NHC11 U R represents the residue of a polyether polyol, polylactone polyol, poly(acrylate)polyol polysiloxane polyol or poly(glycidyl ether)polyol, having at least a+b hydroxyl groups, the residue formed by removal of hydrogen from the hydroxyl groups, the polyol having a number average molecular weight between 90 and 10,000, and a hydroxy equivalent weight of from 45 to 5,000, 30 A represents a carboxylic acid containing group, a is a number having an average value between 2 and 20, and b is a number having an average value between 0.3 and 10.

A general method of preparing oligomers of the present invention is as follows.

Step One - Preparation of a one-to-one adduct of a hydroxyalkyl (free radical polymerizable) material and a polyisocyanate, preferably a diisocyanate. This is done by reacting the two materials in a one-to-one ratio.

Step Two - Reaction of an organic polyol having X number of hydroxyl groups with up to X-1 moles of the adduct of Step One. This forms a urethane oligomer having both ethylenically unsubstituted groups and at least one free hydroxyl group. Although, of course, in this reaction some 40 individual oligomeric moieties may have all X hydroxyl groups reacted with the isocyanate, by control of the proportions of isocyanate adduct and polyol, the number average of free hydroxyl groups on the urethane oligomer will be at least one.

6 GB 2 104 086 A 6 Step Three - The free hydroxyl groups on the product of Step Two are esterified with a polycarboxylic acid (preferably a dicarboxylic acid and most preferably an anhydride of a diacid). This reaction forms the carboxyi-substituted, ethylenically unsaturated urethane oligomer of the invention.

The adduct of the hydroxyalkylacrylate and the diisocyanate of Step One has the general formula:

0 0 OCN-R6-NHC--0(R'O) OCC=CH, 5 i R 4 wherein R 6, R 4 and a are as defined above, and R' is preferably tolVI, and R is an aliphatic group and preferably is (CH,),-, 10 It is preferred to use diisocyanates such as tolyiene-2,4-dilsocyanate and isophorone diisocyanate because of the great differential between reactivities of the isocyanate groups thereon. Without this differential, the product would have to be purified or else there would be less control over the subsequent product. Such adducts are prepared by the addition of about 0. 9 to 1. 1 molar equivalent of the hydroxyalkylacrylate to one mole of organic diisocyanate while stirring the reaction mixture. Generally, 15 it is desirable to hold the temperature below about 300C during the addition. The reaction can be complete after stirring the mixture for 10 minutes to an hour or more. If not completed that quickly, the reaction may be completed by further heating the mixture at temperatures of 501 or more for at least an hour. Since many of the reaction products are viscous liquids or solids (the reaction product of 2 hydroxyethyl methacrylate and 2,4-toluene-diisocyanate is a solid) it is preferable to add 0.25 to about 20 parts by weight of a non-functional group containing solvent, such as methylethyl ketone, acetone, tetra hydrofu rane or the like. The solvent can be added at the beginning of the reaction, or along with the addition of the hydroxyalkylacrylate. Although not always necessary, it is often desirable to add a catalyst to effect the reaction between the hydroxyl group of the hydroxyalkylacrylate and one of the isocyanate groups of the organic diisocyanate. Suitable catalysts for the teaction are well known; an 25 example of which is dibuty[tin dilaurate.

Step Two is accomplished by adding over a period of one to five or more hours either the product of Step One to an organic polyol as defined above while heating the mixture at about 50 to 1000 or vice-versa. As for Step One, a catalyst such as dibutyltin dilaurate can be used to facilitate the reaction.

It is often desirable to add a polymerization inhibitor such as 2,6-d i (tbutyi)-4-methyl phenol to prevent 30 premature polymerization. The ratio of diisocyanate-hydroxyalkylacrylate adduct to organic polyol is chosen so that one mole of oligomer obtained by the reaction contains at least two acrylic groups but leaves at least 0.3 equivalents unreacted hydroxyl groups.

Step Three is carried out, generally without isolating the product of Step Two, by esterification of unreacted hydroxyls in the product of Step Two with an anhydride of a dicarboxylic acid. Preferably, the 35 esterification is accomplished by adding an amount of an anhydride of a dicarboxylic acid such as preferably succinic acid anhydride or adipic acid anhydride and continuing heating 50 to 1 001C for 3 to about 10 hours, the higher the temperature, the shorter the heating time required. Depending on the extent of carboxylation desired, there is used from about 0.3 to about 4 moles of anhydride per mole of organic polyol originally present in the reaction mixture. The esterification, however, can be preformed 40 using in place of the anhydride an ester of the dicarboxylic acid, viz., the methyl or ethyl ester and by ester interchange distil[ off the corresponding methanol or ethanol formed. Esterification can also be performed using other reactive derivatives of the dicarboxylic acid such as the diacid chloride and removing the hydrogen chloride formed. Sometimes it is necessary to add a basic catalyst, such as lithium acetate, to increase the rate of this reaction.

Controlling the ratio of the number of acid (carboxylic acid) groups on the oligomer to the gram molecular weight of the oligomer is an effective way of controlling the bonclabifity of the composition to a substrate after photoinitiated reaction. With increasing acid concentration, the composition is removed more easily in development. A wide range of ratios can be used, depending upon the performance characteristics desired in the final product. A composition having a ratio of molecular weight to acid groups between 67 and 17,000 is useful. It is preferred to have the ratio of molecular weight to acid groups in the oligomer between 500 and 5,000, and most preferably between 800 and 3,000.

Binders The second of the critical elements in the photopolymerizable compositions of British Application 55 No. 7914903 is the binder. This material is an organic film forming polymer generally having a molecular weight of at least 6,000, preferably 12,000 and most preferably at least 15,000. It is desirable, but not essential for practice of the present invention, for the binder to have a labile hydrogen 7 GB 2 104 086 A 7 or easily abstractable hydrogen thereon. The polymer preferably has a molecular weight of no greater than 100,000, preferably no greater than 80,000 and most preferably no greater than 50,000, although binders with molecular weights up to 2,000,000 or 3,000,000, are known in the art. To be a labile or easily abstractable hydrogen, a hydrogen in the binder must be attached to a carbon atom having an adjacent heteroatom selected from N, S, Se, and 0. Preferably the heteroatom is N, S, or 0. It 5 is also preferred that the carbon having the easily abstractable hydrogen thereon is in a 5, 6, or 7membered heterocyclic ring comprised of Q N, S, and 0 atoms, with preferably two heteroatoms adjacent to the carbon atom having the labile hydrogen. The carbon atom bearing the labile hydrogen can be primary, but is preferably secondary or tertiary. The greater the ease of abstractability the lower the proportion of binder that the composition needs, although not necessarily in a linear relationship.10 Preferred binders are the polyvinyl acetals such as polyvinyl formal, polyvinyl butyral, and mixtures thereof. Poly-(vinyl methylether), polyvinyl alcohol, hydroxyalkylcellulose (e.g., hyd roxypropylcel 1 u lose), polyamides, polyvinyl acetate, polyvinyl acetate-polyvi nyl chloride copolymers, polyethyleneoxides, and polyacrylates (e.g. polyalkylmethacrylates have also been found to work well).

The rate or quantum efficiency of double bond conversion (i.e., polymerization) and the photosensitivity of various coatings exposed in air are a function of the type of polymeric binder used.

While some polymers give no increase in rate and photosensitivity to the composition, many polymers have been found that give surprisingly large increases. Amongst the polymers that have been shown to give an increase in the rate of conversion of double bonds include polyvinylacetals, polyvinylalcohol, hydroxyalkylcellulose (e.g., hyd roxypropylce 11 u lose), polymides, polyvinylacetate, polyvinylacetatevinylchloride, polyethyleneoxide, and polyalkylmethacrylates. Polymers that do not give an increase include certain aliphatic hydrocarbon resins, cellulose acetatebutyrate, certain polyurethanes such as Estanel, and linear saturated polyesters.

It should be understood by those knowledgeable in the art that not all polymers that give a rate increase are necessarily the best binders for lithographic plate coatings although they are still useful 25 and desirable in other imaging processes such as duplicating film and proofing systems. Other properties such as solubility, water sensitivity and adhesion must be considered in choosing a polymeric binder for lithographic plates.

The exact function of the binder in the compositions is not understood. The labile hydrogen thereon is believed to be desirable, as many materials without a labile hydrogen do not appear to work 30 as well as those with labile hydrogens, although some do in fact work well. Oxygen barrier characteristics may be additionally desirable in the binder polymer but such characteristics are not known to be essential.

Monomers Another of the critical materials in the photopolymerizable compositions of British Application NO. 35 7914903 is the monomer. This material is a free radical polymerizable monomer having one or more ethylenically unsaturated groups, and preferably 2 to 4 ethylenicaily unsaturated groups such as acrylate, methacrylate, vinyl and allyi. Preferred are compounds having multiple acrylate and methacrylate groups, e.g., acrylic esters of low molecular weight polyols, such as.

trimethylolpropanetriacrylate, pentaerythritol tetraacrylate and triacrylate, etc. Preferably these monomers have a molecular weight of less than 2,000 and more preferably less than 1,000.

Suitable free radical polymerizable monomers useful in such compositions are well known and listed in many patents, e.g., U.S. Patent Nos. 3,895,949 and 4,037,021. Preferred monomers are the polyacrylate and polymethacrylate esters of alkanepolyols, e.g., pentaerythritol tetraacrylate, tris(2 acryloxyethyi)-isocyanurate, tris(2-methya cry] oxyethyi)-Isocyan u rate, 2-acetoxyethyl methacrylate, 45 tetra hydrofu rfu ryi-m ethacryl ate, 1 -aza-5-acryloxymethy]-3,7dioxabicyclo[3.O.Oloctane (ADOZ) bis[4 (2-acryloxyethyl) phenyl] di methyl methane, diacetone acrylamide, and acrylamidoethyl methacrylate.

Initiator The compositions of British Application No. 7914903 must also have a radiation sensitive system capable of initiating free radical polymerization upon absorption of radiation. Free radical initiators are 50 materials known in the art, such as Free-Radical Chemistry, D. C.Nonhebel and J. C. Walton, University Press (1974). Particularly suitable free radical generators can be selected from many classes of organic compounds including, for example, organic peroxides, azo compounds, aromatic diazonium salts, aromatic iodonium salts, aromatic sulfonium salts, aromatic phosphonium salts, quinones, benzophenones, nitroso compounds, acyl halides, aryl halides, hydrazones, mercapto compounds, pyrylium compounds, triarylimidazoles, Mmidazoles, chloroalkyltriazines, etc. These materials, in general, must have photosensitizers therewith to form a photoinitiator system. Photosensitizers are well known in the art.

Additional reference in the art to free radical photoinitiator systems for ethylenically unsaturated compounds are included in U.S. Patent No. 3,887,450 (e.g., column 4), U.S. Patent No. 3,895,949 60 (e.g., column 7), and U.S. Patent No. 4,043,819. Preferred initiators are the onium salts as disclosed in U.S. Patents Nos. 3,729,313; 4,058,400; and 4,058,40 1. Other desirable initiators are biimidazoles (disclosed in U.S. Patent Application Serial No. 824,733, filed August 15, 1977) and 8 GB 2 104 086 A 8 chioroalkyltriazines as disclosed in U.S. Patent No. 3,775,113. These references also disclose sensitizers therein. Another good reference to photoinitiator systems is Light-Sensitive Systems, J. Kosar, 1965, J. Wiley and Sons, Inc., especially Chapter 5.

Preparation 1 A polycaprolactone hexol is prepared for use in forming a carboxyl substituted urethane oligomer.

63.5 grams dipentaerythritol, 228 grams epsilon-caprolactone, and 0.02 grams 2,6-di-t-butyi-4 methyl phenol (as an oxidation inhibitor were added to a 500 mi, three- neck flask which had been fitted with an overhead mechanical stirrer and a condenser. The liquid was deoxygenated for 20 minutes by bubbling with dry nitrogen from a gas dispersion tube. This tube was then replaced with a gas inlet adapter and the reaction mixture was heated while maintaining a slight positive pressure with 10 nitrogen. The mixture was maintained at 1700C for 5 hours under continual stirring. The reaction mixture was then allowed to cool to room temperature under a nitrogen atmosphere. This material is referred to as P-1. This procedure is similar to that in U.S. Patent No. 3,169,945.

Preparation 11 A urethane oligomer (hereinafter P-11) was prepared according to the following procedures. 15 A 1000 mI three-neck flask was fitted with an adapter, mechanical stirrer, thermometer, addition funnel, and drying tube. To this flask was charged 175 grams of polycaprolactone hexol P-1 and 60 mi of methylethyl ketone. A solution of 13 grams of 2,4-tolyiene diisocyanate in 9 mi of methylethyl ketone was slowly dripped into the first solution with stirring at room temperature. The addition was completed in 20 minutes and the reaction mixture stirred for 90 minutes at 301C, after which time infrared spectroscopy showed that essentially all the isocyanate had reacted.

To a second flask fitted with an overhead mechanical stirrer, thermometer, addition funnel, and drying tube was charged 86.1 grams of 2,4-tolylene diisocyanate. To the addition funnel was added 70.2 grams of 2-hydroxyethyimethacrylate (hereafter HEMA) and 0.02 grams of the inhibitor of the previous preparation, which was then slowly added with stirring to the dlisocyanate while maintained 25 below or at 301C. The addition was completed in 15 minutes and after 40 minutes of reaction time, a white solid formed. The solid was dissolved in 45 mi of methylethyl ketone by heating to 451C and held at that temperature for 10 minutes to complete the reaction.

The flask containing the reaction product (adduct) of the polycaproiactone hexol (P-1) and the 2,4 tolylene diisocyanate was heated at 671C and the solution of the HEMA/2,4- tolylene diisocyanate 30 adduct in methylethyl ketone was added slowly with stirring over a period of 2 hours. 27 grams of succinic anhydride was then added with an additional 0.02 grams of the inhibitor. Heating and stirring was continued until the anhydride had completely reacted (about 5-6 hours).

The final product is a carboxyl substituted urethane oligomer, P-11.

Preparation Ill The preparation of a second carboxyl substituted urethane oligomer is here described.

To a 500 mi three-neck flask was charged 29.2 grams of a poly(propylene oxide)triol having a molecular weight of 740, 25 mI ethyl acetate, and 0.007 grams of methyl hyd roqu inone as a reaction inhibitor. The flask was heated in a 650C oil bath with stirring and 13.0 grams HEMA and 17.4 grams tolylene diisocyanate were added simultaneously from addition funnels. After addition of one half of 40 these reactants, the reaction mixture was stirred for another 30 minutes. Then 0.001 grams SnCl, catalyst and 0.004 grams 3,4-epoxycyclohexyimethyi-3,4-epoxycyclohexane carboxylate were added.

The reaction mixture was stirred another 30 minutes and then the remainder of the HEMA and diisocyanate were added slowly. Stirring was continued overnight. Infrared analysis showed no free isocyanate groups after that time. To this reaction mixture was added, with stirring, 1.4 grams succinic 45 anhydride. The temperature was raised to 931C and held there until the anhydride was completely reacted. The mixture was then cooled and diluted to 50% weight solution of P-111 oligomer in ethyl acetate.

Preparation IV A 250 mi flask was charged with 21.2 grams of a polycaprolactone polyol having a molecular 50 weight of about 540, 25.1 mi of ethyl acetate and 0.007 grams methylhydroquinone as an antioxidant.

17.4 grams of tolyiene-2,4-diisocyanate and 13.0 grams of 2hydroxyethyimethacrylate (HEMA) were individually added to addition funnels on the flask. The polyol solution was heated to 671C and the diisocyanate and HEMA were added dropwise with rapid stirring until half of each material was added.

At this point stirring and heating were continued for 30 minutes. 0.002 grams SnCl, and 0.008 grams of 3,4-epoxycycl ohexyl methyl -3,4epoxycyclohexane carboxylate were added and the solution stirred for another 30 minutes. The remainder of the diisocyanate and HEMA was added dropwise and then an additional 5 mi of ethyl acetate was added. The mixture was stirred at 671C overnight. When isocyanate was no longer detectable by infrared analysis, 1.4 grams of succinic anhydride was added along with 10 mi of ethyl acetate. The temperature was raised to 1 001C and the reaction of the 60 anhydride was indicated by infrared analysis as essentially complete after five hours.

9 GB 2 104 086 A 9 This resulting material, a carboxylic substituted urethane oligomer, is referred to as P-W and is useful in the practice of the present invention.

Preparation V A particularly useful binder material for the oligomers was prepared as follows. A low molecular weight polyvinyl alcohol (88% hydrolyzed polyvinylacetate) was reacted with butyraidehyde and acrolein using an acid catalyst, preferably sulfuric acid. The proportion of reactants was 100/43.2/6.4 respectively, The product was precipitated from water with a dilute weak basic solution (Na-HC03). Analysis of the product showed the empirical formula to be close to that based on the stoichiometry of the reaction, 0 11 0 - c - CH3 10 CH 2CH2CH3 CE This material is hereinafter referred to as P-9 Preparations V11-Xl L 2 Six additional oligomers were prepared for evaluation in the present invention.

P-V1 was prepared by first placing 128.8 g of 2,4-toluenediisocyanate into a three-neck, 250 m] flask equipped with a mechanical stirrer and a pressure equalizing dropping funnel. The flask was maintained at room temperature with a water bath. Hydroxyethyl metha cryl ate (106.6 g) and 0.089 butylated hydroxy toluene and 100 g methylethyl ketone were added slowly over a 30 minute period.

The reaction was stirred for one hour at room temperature. Methylethyl ketone was added and the reaction mixture was heated to 450C for 3 hours to complete the reaction.

P-] (350 9 of 79% solids in methylethyl ketone) was placed into a 500 mi, three-neck flask 20 equipped with a mechanical stirrer, pressure equalizing dropping funnel and 26.0 g 2,4 toluenediisocyanate was added over a 30 minute period. The temperature rose'to 321C. The mixture was cooled to room temperature and stirred over the weekend. The first reaction product from the above synthesis was added over a four hour period to this second solution which had been heated to 650 C. Heating was continued for ten hours to form the second reaction product. 25 1.8 g of succinic anhydride and 0.1 g lithium acetate were added to 112.4 g (71 % solids in methylethyl ketone) of the second reaction product and the entire mixture heated to 7811C for twelve hours to complete the reaction and form oligomer P-Vi.

P-Vil was prepared by placing 112.4 g (7 1 % solids in methylethyl ketone) of the second reaction product in the preparation of P-V1 into a 500 mi three-neck flask with stirrer and condenser and then 30 adding 2.4 g succinic anhydride and 0.1 g lithium acetate. The mixture was heated to 780C for 12 hours until the reaction was complete to form PWIL PWII I was formed by placing 112.4 g (71 % solids in methylethyl ketone) of the second reaction product in the preparation of P-V1 into a 500 mi three-neck flask with stirrer and condenser with 5.5 g succinic anhydride and 0.1 g lithium acetate. The reaction mixture was then heated to 781C for 32 35 hours until the reaction was complete to form PWIll.

P-1X was formed by first preparing a polycaprolactone hexol by introducing 342 g caprolactone and 127 g dipentaerythritol into a 1000 mi reaction kettle equipped with a thermometer, mechanical stirrer and condenser. The reaction mixture was deoxygenated by bubbling dry nitrogen through a gas dispersion tube for about 30 minutes. The gas dispersion tube was then replaced with a gas inlet adapter and the reaction was maintained under a slight positive nitrogen pressure. The reaction mixture was heated in an oil bath at 165-1 701C with continuous stirring for 24 hours. The product was allowed to cool to room temperature while under a nitrogen atmosphere.

14 1.0 g of the polycaprolactone hexol and 50 g of methylethyl ketone were placed in a 1000 mi flask equipped with a pressure equalizing dropping funnel and a mechanical stirrer. This solution was maintained at room temperature by using a water bath while 2,4-toluene diisocyanate (13.0 g) in 20 g of methylethyl ketone was added over a 25 minute period through the dropping funnel with continuous stirring. Stirring at room temperature was continued for 22 hours to form the second reaction product.

38.2 g of 2,4-toluene diisocyanate and 0.2 butylated hydroxytoluene were introduced into a 250 mi three-neck flask equipped with mechanical stirrer, pressure equalizing dropping funnel and thermometer. Hydroxyethyl methacrylate (31.2 g) was added with continuous stirring over fifteen minutes at a temperature below 301C. The mixture was stirred for one hour and a white solid formed.

mi of methylethyl ketone was added and the mixture heated to 450C for three hours to complete formation of the third reaction product.

69.7 g of the second reaction product and 0.02 g butylated hydroxy toluene were added to a 55 500 m] three-neck flask with a mechanical stirrer, condenser, and pressure equalizing dropping funnel.

This solution was heated to 691C with continuous stirring. The entire portion of the third reaction GB 2 104 086 A 10 product was added to this solution over one hour. Heating and stirring were continued for thirteen hours to form the fourth reaction product.

13.0 g of succinic anhydride and 0.4 g of lithium acetate were added to the fourth reaction product and the solution heated at 701C to 801C with continuous stirring to form PAX.

P-X was prepared by first forming a polyol by placing 93.1 g tripentaerythritol and 303.2 g 5 caprolactone in a 1 liter reaction kettle equipped with mechanical stirrer, condenser, and thermometer.

The reaction mixture was purged with dry nitrogen for 30 minutes, and a gas inlet tube affixed thereto.

Positive nitrogen pressure was maintained over the reaction mixture as it was heated to 165-1 701C for 9-1/2 hours, then allowed to cool to room temperature.

300 g of this polyol and 75 g of methylethyl ketone were introduced into a 1000 mi flask 10 equipped with stirrer, dropping funnel and thermometer. 16.4 g of 2,4- toluene diisocyanate was added through the dropping funnel over 10 minutes. The temperature of the mixture rose to between 28 320C and continued for about 3-1/2 hours to form the first reaction product. 153 g of this product (as 80% solids in methylethyl ketone) was added with 0.04 g butylated hydroxytoluene into a flask and heated to 65-700C. Over a period of 2 hours the third reaction product of preparation IX was added 15 to this solution and heated for an additional three hours.

18.5 g of succinic anhydride and 0.5 g of lithium acetate was added to the above resulting solution and the mixture heated at 70-801)C for 22 hours to product P-X.

P-X] was prepared by first forming an adduct of 2,4-toluene diisocyanate (26.8 g) and hydroxyethyimethacrylate (22 g) in 30 mi of methylethyl ketone with 0.02 g butylated hydroxytoluene in the same procedure used in forming the third reaction product of preparation IX. This product was added over a one hour period to the product of the second solution of PVI (87.7 g as 80% solids in methylethyl ketone) and 0.02 g butylated hydroxytoluene and heated to 65- 701C. Heating was continued for 7-1/2 hours at about 67 'C.

19.6 g of succinic anhydride and 0.4 g lithium acetate were then added to the solution and 25 heated at 750C for 84 hours to form P-Xl.

Preparation XIII A urethane oligomer (hereinafter P-Xli) was prepared according to the following procedure.

A 1000 mi three-neck flask with adapter fitted with an overhead mechanical stirrer, thermometer, addition funnel and drying tube was charged with 180 g of a polypropylene oxide 1301Y01 30 of molecular weight 600 and 90 mi of methylethyl ketone. A solution of 34. 8 g 2,4-toluene diisocyanate in 30 g of methylethyl ketone was added with stirring at room temperature. The addition was completed after 80 minutes and stirring was continued at room temperature for 90 minutes. After the addition of 0.02 g 2,6-d i-t-b utyl -4-m ethyl phenol, the temperature was increased to 45-551C for about 15 hours at which time isocyanate groups were no longer detected by infrared analysis.

To a 250 mI one-neck flask with a magnetic stirrer and drying tube was charged 95.7 g 2,4toluene diisocyanate. 78 g of 2-hydroxyethyl methacryl ate was added over a period of about 10 minutes while maintaining the temperature at less than 301 C with a cold water bath. After about 40 minutes of total reaction time a white solid formed and 45 mi of methylethyl ketone was added. The solution solidified on standing overnight and was redissolved by warming to about 451C.

The product from the reaction of the polyol and 2,4-toluene diisocyanate was heated to 670C and the product from the 2-hydroxyethyimethacrylate and 2,4-toluene diisocyanate was added over a period of about 30 minutes. After 6 hours 27 g of succinic anhydride and 1.05 g of lithium acetate weie added. After about 28 hours of heating at 530C to 701'C the anhydride was determined to be completely reacted by infrared analysis.

Examples 1-4

A solution was prepared (in parts by weight) from 3.32 parts pentaerythritol tetraacrylate, 1.87 parts P-11, 0.17 parts triethylamine, 0.34 parts of diphenyliodonium hexafluorophosphate, 0.17 parts 4,4'-bis(dimethylamino)benzophenone (a photosensitizer for the iodonium catalyst) and 91.62 parts of n-propanol/water azeotrope (71.8% n-propanol and 28.2% water). Aliquots of this solution were prepared and 2.50 parts by weight of different organic polymeric binders were added to the solution.

Aluminum sheets which had been grained and anodized were coated with these solutions using a #14 wire wound rod and then dried with a heat gun. The coated aluminum was then exposed for 13 seconds in a vacuum frame to a carbon arc having about 5000 watt output and at about 1 meter distance through a 21 step sensitivity guide and a neutral density 0.51 filter. Exposed plates were developed by wiping with a weak basic aqueous solution of 0.63% sodium metasilicate and 0.23% sodium (lower alkyl) naphthalene sulfonate.

The binders used in the examples were:

1. P-V; 2. Poly(vinyl methyl ether), 3. Poly(vinyl formal), prepared from a polyvinyl acetate starting material and having 85% of the acetate groups replaced by alcohol and formal groups (the polyvinyl acetate having a viscosity of about 12 cp at 250C, as 86 grams in 1000 mi of benzene), and 4 11 GB 2 104 086 A 11 4. Poly(vinyl butyral).

The following table shows the polymer retained after exposure to a certain number of steps and development by the weak basic solution.

Steps Example Solid Ghost 5 1 8 10 2 4 3 4 4 2 6 5 4 The "ghost" values indicate the lowest exposure from which photopolymer was retained on the 10 plate. The "solid" values indicate the exposure level at which the developed image density can no longer be differentiated from the background and is believed to be cured to the desired level.

The numbers of the steps consecutively indicate an increase of about 40% in filtering strength. The higher the step number remaining after development, the correspondingly higher sensitivity of the composition exposed and developed.

Example 5

The usefulness of the compositions of the present invention in conventional newspaper printing operations was evaluated here.

A solution was prepared having 17.2 grams pentaerythritol tetraacrylate, 13.5 grams P-11 (70% by weight in methylethyl ketone), 171.6 grams of polyvinyl format in a 6% by weight solution in the 20 azeotrope, 295 grams of the n-propanol/water azeotrope, 4.3 grams of 20% triethylamine, 3.7 grams of red pigment (Pigment Red 48, Cl 15865 in the Color Index) in a composition of 1:2 weight ratio to polyvinyl formal (as described above), 1.74 grams diphenyliodonlum hexafluorophosphate and 0.65 grams 4,4-bis(d i methyl am!no) benzophenone photosensitizer. This composition was coated on grained anodized aluminum using a squeeze roll coater fitted with a rubber gravure sleeve. The coating weight 25 was about 1.72 grams/m'. The coating was exposed in a vacuum frame by a carbon arc for 40 seconds through a neutral density 0.5 filter and a newspaper negative. The coating was developed with the aqueous developing solution of Examples 1-4 and then gummed with a standard subtractive plate gum. The resulting printing plate was mounted on a high speed web press using direct lithographic techniques and produced 95,000 newspaper impression without degradation of the image line copy or 30 half-tones.

Example 6

A solution was prepared from 7.72 grams of P-V, 327.4 grams of the npropanol/water azeotrope, 12.8 grams of pentaerythritol tetraacrylate, 10.3 grams of a 69% by weight solution of P-11 in the azeotrope, 3.2 grams of a 20% solution of triethylamine in the azeotrope, 15.7 grams of Pigment 35 Red 48 dispersed in P-V and the azeotrope (4:8:88), 1.3 grams of diphenyliodonium hexafluorophosphate and 0.65 grams of the benzophenone sensitizer of the previous examples. This solution was coated onto grained anodized aluminum using a squeeze roll coater fitted with a rubber gravure sleeve at a coating weight of about 1.72 grams/m'. The coatings were exposed from a pasteup with a laser imaging system, using primarily the 351 and 364 nm lines of an argon ion laser, (at 4 milliJoules/cM2 exposure) and developed with the mild basic aqueous developing solution of the previous examples, and gummed with a commercial subtractive plate gum. The printing plates were mounted on a web offset press and produced high quality impressions.

Example 7

A solution was prepared from 12.8 grams of polyvinyl formal from a 6% by weight solution in the 45 n-propanol/water azeotrope, 1.28 grams of pentaerythritol tetraacrylate, 1.42 grams of P-111 as a 50% by weight solution in ethyl acetate, 24 grams of the azeotropic solution, 0.28 grams of Pigment Red 48 in polyvinyl formal (1:2 weight ratio), 8 drops of a 20% solution of triethylamine in the azeotrope, 0. 13 grams of diphenyllodonium hexafluorophosphate and 0.065 grams of the benzophenone sensitizer of the previous examples.

This solution was coated onto grained anodized aluminum using the #14 wire wound rod. After exposure (from a 5000 watt output carbon are for 13 second through neutral density 0.51 filter) and development with the weak basic solution of the previous examples, a solid image at step 6 was obtained, and a ghost image at step 7 was obtained.

Example 8

A solution was prepared from 1.54 grams of P-V, 2.56 grams of pentaerythritol tetraacrylate, 2.06 grams of P-11 as a 70% by weight solution in methylethyl ketone, 0.64 grams of triethylamine as a 12 GB 2 104 086 A 12 20% by weight solution in the azeotrope, 4.7 grams of a dispersion of Pigment Red 48 in P-V and the azeotrope W8:88), 65.6 grams of the azeotrope, 0.25 grams of diphenyliodonium hexafluorophosphate, and 0.13 grams of 4,4'-bis(dimethylamino)benzophenone. This solution was coated with a #14 wire wound rod onto a substrata comprising polyethylene film with a top coat of Ti02 and CaCO, in a polyurethane binder. This coating was air dried with a heat gun and overcoated with a 10% solution of low molecular weight (88% hydrolyzed polyvinyl acetate) poly(vinyl alcohol) with a small amount of inert surfactant as a coating aid. A 10 wire wound rod was used to coat this solution. The dried coating was exposed in a vacuum frame to a carbon arc for 13 seconds through a 0.5 neutral density filter, a half- tone negative, and a sensitivity guide. The exposed coating was developed with an aqueous solution of 0.63% sodium metasilicate and 0.23% sodium (lower alkyl)naphthalene suifonate. A strong magenta image on a white background was obtained. Solid 3 and ghost 5 steps were visible and sharp 3-97% dots of at least a 110 line screen were obtained.

Examples 9-15

The following examples show the necessity and interaction of the different components of the system of the present invention. The effect of polyMnyl alcohol) top-coats, normally used in the art as an oxygen barrier, was also investigated.

Solutions were prepared with different combinations of representative additives. P-V was used as the binder, P-11 as the carboxyl containing free radical polymerizable oligomer, pentaerythritoi tetraacrylate as the free radical polymerizable monomer, diphenyliodonium hexafluorophosphate (as 20 0.04 parts by weight) as the free radical initiator, e:5s 8 S-_r S U1 NI>- N - C7H15 1 0 2"5 2 CO 2 H hereinafter referred to as CEBH (0.01 parts by weight) as sensitizer, and poly(vinyl alcohol) as a topcoat. The solutions having the compositions noted below in the table were coated on grained and anodized aluminum to give a dry coating weights of from 1.06 to 1.61 gra MS/M2. Where a topcoat was present, the poly(vinyl alcohol) was applied at about the same coating weight as the base coat. In the 25 examples the solutions were made from isopropanol or methanol-methylethyl ketone-water solvents.

Triethylamine was added in all examples in amounts equivalent to the acid in PAL The dried samples were exposed through a 21 step sensitivity guide for 2 seconds with a 16,000 foot candle tungsten source. The exposed samples were developed by wiping with an aqueous solution of 0.35% sodium metasilicate and 0.25% sodium (lower a 1 kyl) naphthalene sulfonate.

Example No. P-V P41 Monomer Top coat Steps 9 0.3 0.0 0.4 No 1 0.3 0.4 0.0 No 1 11 0.0 0.5 0.4 No 0 12 0.0 0.5 0.4 Yes 10 35 13 0.3 0.2 0.4 No 9 14 0.3 0.4 0.2 No 10-11 0.3 0.4 0.2 Yes 14 As can be seen from these results, the absence of any one of the three ingredients (binder, oligomer, or monomer) produces poor or useless photopolymerizable compositions. When a top coat is 40 put on the composition without the binder (Example 12), the oxygen sensitivity of the system is reduced and it polymerizes well. Surprisingly, systems having the three components of the present invention work as well as the top coated system (Examples 13 and 14), and when the systems of the present invention are combined with a top coat, even further improved results are obtained (Example 15). These results are surprising and highly desirable.

Example 16

A solution was prepared from 4 parts poly(m-di alyl phtha late), 2 parts P-11, 4 parts pentaerythritol tetraacrylate, 5 parts methanol, 0.4 parts diphenyliodonium hexafluorophosphate, 0.1 part CEBH, 0.4 parts of Phthalocyanine Blue GS, and methylethyl ketone to 100 parts. This was coated onto grained and anodized aluminum to give a dry coating weight of about 1.34 grams/m'. This was overcoated with poly(vinyl alcohol) at about the same coating weight as the base coat. The coating was air dried, then exposed and developed as in Examples 9-15.

The photopolymer was retained through step 12.

Example 17

The same procedure as in Example 16 was used except that 4 parts of trismethacryloxyethyl 55 13 GB 2 104 086 A 13 isocyanurate was substituted for the pentaerythritol tetraacrylate. The photopolymer was again retained through step 12.

Examples 18-21 A solution was prepared from 0.3 grams P-V, 0.4 grams pentaerythritol tetraacrylate, 0.22 grams P-11, 0.04 grams diphenyliodonium hexafluorophosphate, 0.02 grams of CEBH, 1.28 grams methylethyl 5 ketone, 0.47 grams water, 7.36 grams lsopropanol, and 6 drops of a 20% by weight solution of triethylamine in n-propanol. The solution was coated with wire wound rods onto grained and anodized aluminum at coating weights of 0.95, 1.36 and 2.04 gra MS/M2. Some of the coatings were overcoated with a 10% by weight solution of poly(vinyl alcohol) using a 8 wire wound rod. The coatings were exposed using an argon laser at 488 nm and developed by wiping with a pad and an aqueous solution 10 of a 0.35% sodium metasilicate and 0.25% sodium (lower alkyl)naphthalene sulfonate. The laser beam was passed through a 21 step sensitivity guide. The exposure values (in miii!JouleS/CM2) listed are the exposures needed to give a solid step 6 for the various coating weights.

Coating weight Example g/M2 Top coat Exposure 15 18.95 Yes 1.8 19 1.36 Yes 1.8 1.36 No 10-14 21 2.04 No 10 As can be seen, the top coat improves the compositions, but the uncoated materials are still of 20 excellent speed and quality even when exposed in the presence of air.

Examples 22-32 Solutions were prepared as in Example 16 except that different photoinitlation systems were evaluated. Exposure was to a mercury vapor lamp having an output of 500 watts/inch at a distance of about 34 cm through an interference filter having a maximum transmission at 366 nm and a 21 step sensitivity guide. The table indicates the relative sensitivity of the system for the minimum exposure required to give retained photopolymer with development as in Example 16.

Approx.

absorption Relative Ex. Photoinitlation system at 366 nm exposure 30 22 4,4'-bis(dimethylamino) 0.3 0.26 benzophenone 2-o-chlorophenyl-4,5-di (m-methoxyphenyi)imidazole dimer 35 2-o-chlorophenyl-4,5-diphenylimidazole dimer 2-mercaptobenzoxazole 23 Same as Example 22' 0.01 0.88 24 4,4'-bis(dimethylamino) 0.1 2.2 40 benzophenone diphenyliodonium hexafluoro phosphate tetraphenyl benzidine 0.2 3.3 diphenyliodonium hexa45 fluorophosphate 26 tetra phenyl benzidin e 0.1 4.8 diphenyliodonium hexa fluorophosphate 27 tetraphenyl benzidine 0.02 13 50 diphenyliodonium hexa fluorophosphate 14 GB 2 104 086 A 14 Approx.

absorption Relative Ex. Photoinitiation system at 366 nm exposure 28 2,4-bis(trichloromethyi)-6- 0.2 6.6 (4-methoxyistyryl)-s- 5 triazine 29 3-carboxymethyi-5(3-ethyi- 0.02 13 2-benzothiazolinylidene) 2-(3-hepty]-4-oxo-2-thio 5-thiazolinylidene)-4- 10 thiazolidone diphenyliodonium hexa fluorophosphate chlorothioxanthone 0.2 9 diphenyliodonium hexa- 15 fluorophosphate 31 ethyldimethoxy anthracene0.02 40 diphenyliodonium hexa fluorophosphate 32 4,4-bis(dimethylamino)0.1 40 20 benzophenone Examples 33-39 A stock solution was prepared by mixing 5.13 grams pentaerythritol tetraacrylate, 4.03 grams P- 11, 25.5 grams of a 10% by weight solution of polyvinyl formal in the azeotropic solution of n-propanol and water, 119 grams of methylethyl ketone and 1.5 grams of a 20% by weight solution of triethylamide in the azeotrope. To aliquots of 20 grams of this solution were added various photoinitiation systems. The photoinitiation systems and amount of each are shown in the following table. The solutions were then coated on a grained anodized aluminum substrata with a #14 wire wound rod and dried with a heat gun. The resulting coatings were exposed for 13 seconds to a carbon arc through a 21 step sensitivity guide and a 0.5 density filter. The exposed coatings were developed 30 by wiping with an aqueous solution of 0.63% by weight sodium metasilicate and 0.23% by weight of sodium (lower alkyOnaphthalene sulfonate. The number of solid steps observed after gumming and inking were recorded. As in previous examples, the higher the number of steps retained, the greater the sensitivity of the coating.

Weight Solid 35 Ex. Photoinitiation system (grams) steps 33 4,4'bis(dimethylamino)benzophenone 0.035 0 34 4,4-bis(di methyl am i no) benzophenone 0.035 7 diphenyliodonium hexafluorophosphate 0.070 35 7-diethylamino-4-methylcoumarin 0.035 0 40 36 7-cliethylamino-4-methylcournarin 0.035 4 diphenyliodonium hexafluorophosphate 0.070 37 2,4-bis(trichloromethyi)-6-(4- 0.070 2 methoxystyryi)-s-triazine 38 2,4-b is(tri c h 1 orom ethyl)- 6-(4- 0.14 3 45 methoxystyryl)-s-triazine 39 4,4'-bis(dimethylamino)benzophenone 0.035 11 2-o-chlorophenyl-4,5-di(m-methoxy- 0.10 phenyl)-imidazole dimer 2-o-ch lorophenyi-4,5-di phenyl 0.10 50 imidazole dimer 2-mercaptobenzoxazole 0.07 None of these compositions had top coats.

Examples 40 and 41 Two additional monomers were evaluated in the compositions of the present invention. Two solutions (A and B) were prepared having the following composition:

1 GB 2 104 086 A 15 P-11 (64% in methylethyl ketone) polyviny[formal (10% in the n-propanol-water azeotrope) P-V (12.9% in n-propanol (62%), isopropanol (10%, and water (28%) dispersion of Pigment Red 48 and polyvinyl formal (10% in the above azeotrope) in a 2/1 parts by weight ratio resin/pigment 4,4'-bis(di methyl am i no) benzophenone diphenyllodonium hexafluorophosphate triethylamine (20% by weight in the azeotrope) n-propanol-water azeotrope Grams 3.12 7.6 4.18 10.0 0.19 0.37 0.96 70.0 To solution A was added 3.67 grams of pentaerylthritol tetraacrylate and to solution B was added 3.67 grams of tris(2-acryloxyethyl isocyanurate). The solutions were then coated onto grained and anodized aluminum using a number 18 wire wound rod and dried for one minute at 651C. The coated plates were then exposed with a 2 kilowatt diazotype lamp for 2, 5, and 10 seconds in air. The exposed 15 plates were developed by washing with an aqueous solution of 3% sodium metasilicate, 3% npropanol, 0.3% sodium dodecyl diphenylether disuifonate, and 0.3% of an alkyl naphthalene sulfonate. The number of solid and ghost steps remaining after development are given in the following table.

2 Sec. 5 Sec. 10 Sec.

Coating solldIghost solidIghost sofidIghost A 4-5 5-7 6-8 20 B 7-8 9-10 9-11 Examples 42 and 43 The usefulness of the compositions of the present invention with lower intensity exposure processes was examined. The compositions as weight percentages were as follows:

Percentage solids 25 Component Solution A Solution 8 pentaerythritol tetraacrylate 43.1 32.3 P-11 23.7 18 P-V 6.25 17.2 polyvinyl formal (10% in the azeotrope) 15.2 17.7 30 pigment dispersion (of Example 40) 3.09 2.8 triethylamine (20% in the azeotrope) 2.15 1.6 diphenyllodonium hexafluorophosphate 4.30 8 4,41 -bis(di methyla m!no) benzophe none 2.14 2 Solution A was dried for one minute at 180OF with a coating weight of 200 mg/ftl. Solution B 35 was dried with a heat gun at a coating weight of 170 mg/ftl. The substrate in both cases was grained and anodized aluminum. A conventional microfilm enlarger was used and the plates were exposed with between 10 and 30 milliwatts/cml irradiance by a mercury xenon lamp through a 21 step sensitivity guide in contact with the plate. Exposure was made in air. The exposed plates were developed by washing with an aqueous solution of 5.25% metasilicate, 6.37% n-propanol, 8.25% glycerol and 40 0.075% alkyl naphthalene sulfonate. The results are reported below.

Exposure time Steps Plate Seconds sofidIghost A 2 3-5 4 4-6 45 6 5-6 8 5-7 B 2 5-7 4 6-8 6 6-8 50 When identical plates were imaged (A for 3 seconds and B for 1 second) with line copy and half tones on an aluminum sheet, 10,000 high quality impressions were obtained with no image loss.

16 GB 2 104 086 A 16 Examples 44-50 A standard solution was prepared having the following weight percentages of ingredients in the n-propanol-water azeotrope:

pentaerythritol tetraacrylate 43.2 P-V 6.35 5 polyvinyl formal (10% in the azeotrope) 15.1 Pigment Red 48 3.1 triethylamine 2.15 diphenyliodonium hexafluorophosphate 4.4 4,4'-bis(di methyl am ino)be nzoph e none 2.2 10 To seven aliquots of this solution were added 23.5 percent by weight of the oligomers P-11 and PV1 through P-Xl. The solutions were coated on grained and anodized aluminum using a number 18 wire wound rod and dried for one minute at 651C. The dry coatings were exposed in air through a 21 step sensitivity guide with a mercury metal halide diazo bulb and developed by wiping with the aqueous developing solution of Example 40. The results are shown in the following table.

Steps Example Ofigomer solidIghost 44 P-V] 4-7 P-VII 4-7 46 P-Vill 3-6 20 47 P-1x 4-5 48 P-H 3-6 49 P-X 4-5 P-Xl 0-2 The above examples show the effect of varying the ratio of acid groups to molecular weight of the 25 oligomer. The first two compositions (Examples 44 and 45) had ratios of acid groups to molecular weight of approximately 1:4300 and 1:3600 respectively and were more difficult to develop than preferred and had a tendency to hold the ink on the background. A stronger or more vigorous developer could correct that tendency. The oligomer of Example 50 had an acid to rfloiecular weight ratio of about 1:750 and developed a little to easily, with much of the photoreacted material being removed. 30 All compositions were useful and could be polymerized in air, however. Examples 46 through 49 worked exceptionally well and had a ratio of the number of acid groups to molecular weight of between about 1:800 and 1:3000, with Example 48 having a ratio of about 1:1200. Compositions without any acid groups do not adhere well to the substrate. Development does not differentiate between exposed and unexposed areas with both being removed indiscriminately. Compositions without ethyienic 35 unsaturation do not photoreact and also do not bind to the plate surface.

Example 51

A solution was prepared like those in Examples 44-50 using P-Xli in place of the oligomers in the above examples. Coatings were exposed and developed as in Examples 44- 50. Only one ghost step and no solid steps were obtained. Prolonged exposure gave more retained steps.

Examples 52-57 A solution was prepared for the comparison of different binder materials. The solution comprised in parts by weight:

pentaerythritol tetraacrylate 41.3 P-11 22.5 45 polyvinyl formal 9.95 Pigment Red 48 2.94 triethylamine 2.05 diphenyliodonium hexafluorophosphate 4.2 4,4'-bis(dimethylamino)benzophenone 2.1 50 selected binders 14.9 The binders selected were 52. P-V 53. low molecular weight hydroxypropyl cellulose 54. polyvinyl butyral (MW 38,000-45,000) 55 17 GB 2 104 086 A 17 55. polyamide WivamideR nylon resin supplied by DuPont Co.) 56. polyvinyl formal 57. no resin The solutions were coated onto salt plates (clear crystals of sodium chloride), dried, and the infrared spectrum determined. The coatings were exposed in air to radiation from a 2 kilowatt mercury 5 metal halide diazo bulb for various times at various irradiances. The infrared specturm was determined after the exposure and the percentage of double bonds converted by the exposure was calculated on the basis of the absorption at 810 cm-'. The results appear below.

Example

52 53 54 55 56 57 Examples 58-69 Percentage of double bonds converted at 9 MWICM2 irradiance 32 32 27 25 15 A solution was prepared for the comparison of different binder materials. The solution comprised in parts by weight:

pentaerythritol tetraacrylate P-11 polyvinyl formal Pigment Red 48 triethylamine diphenyliodonium hexafluorophosphate 4,4'bis(dimethylamino)benzophenone selected polymeric binders The binders selected were 58. P-V 59. polyvinyl pyrol Wone 60. polyvinyl formal 6 1. copolymer of vinyl chloride (81 %) and vinyl acetate (19%) 62. polyvinyl acetate 63. polyethylene oxide (MW24,000,000) 64. polymethyimethacrylate (low molecular weight, inherent viscosity -C0.2) 65. low molecular weight polyolefin resin 66. linear saturated polyester resin 67. thermoplastic aromatic polyurethane 68. cellulose acetate butyrate 69. no resin The results of infrared analysis after coating of these compositions as in Examples 52-57 and exposure to 9 milli Watts/cm' irradiance appears below.

Double bond Example conversion % 58 59 60 61 62 63 64 65 66 67 68 69 30 25 25 25 24 23 16 15 15 13 15 In Examples 52-69, exposure time was 10 seconds. The words "Estane" and--- Elvamide"are Registered Trade Marks.

43.1 23.7 15.0 3.0 2.2 4.4 25 2.2 6.3 18 GB 2 104 086 A 18 Ciaims 1. A polymerizable unsaturated polyurethane of the formula:

0 11 (E-D).R(01--A;b R represents an ethylenically unsaturated, free radical polymerizable group, D represents the residue of a polyisocyanate having at least two of its isocyanate groups reacted to form in which -NHC11 U groups bonded to E and R, R represents the residue of a polyether polyol, polylactone polyol, poly(acrylate) polyol,

Claims (2)

1. polysiloxane polyol or poly(glycidyl ether) polyol having at least a+b

   hydroxyl groups, the residue formed by removal of hydrogen from the hydroxyl groups, the polyol having a number average molecular weight between 90 and 10,000, and a hydroxy equivalent weight of from 45 to 5, 000, A represents a carboxylic acid containing group, a is a number having an average value between 2 and 20, and b is a number having an average value between 0.3 and 10. 2. A compound as claimed in Claim 1 substantially as herein described with reference to any one of the preparations disclosed herein.

   New Claims or Amendments to Claims filed on 30 Sept 1982. 20 Superseded Claims 1 and 2.

   New or Amended Claims:- 1. A polymerizable unsaturated polyurethane of the formula:

   0 11 (E-D),,R(OL-A)b in which 25 E represents an ethylenically unsaturated, free radical polymerizable group, D represents the residue of a polyisocyanate having at least two of its isocyanate groups reacted to form -NHC- 11 U groups bonded to E and R, R represents the residue of a polyether polyol, polylactone polyol, poly(acrylate) polyol, polysiloxane polyol or poly(glycidyl ether) polyol having at least a+b hydroxyl groups, the residue formed by removal of hydrogen from the hydroxyl groups, the polyol having a number average molecular weight between 90 and 10,000, and a hydroxy equivalent weight of from 45 to 5, 000, A represents a carboxylic acid containing group, a is a number having an average value between 2 and 20, and b is a number having an average value between 0.3 and 10.
2. 2. A polyurethane as claimed in Claim 1 substantially as herein described with reference to any one of the preparations disclosed herein.

   Printed for Her Majesty's Stationery Office by the Courier Press, Leamington Spa, 1983. Published by the Patent Office, 25 Southampton Buildings, London, WC2A lAY, from which copies may be obtained