| PATENT ASSIGNEE'S COUNTRY | Germany |
| UPDATE | 05.00 |
| PATENT NUMBER | This data is not available for free |
| PATENT GRANT DATE | 23.05.00 |
| PATENT TITLE |
Radiation curing of dihydrofuran derivatives |
| PATENT ABSTRACT |
Process for producing coatings or moldings by radiation curing, which involves using high-energy light to irradiate radiation-curable compositions containing 1-100% by weight, based on the total amount of free-radically or cationically polymerizable compounds, of compounds A) containing at least one cationically polymerizable 2,3-dihydrofuran group. |
| PATENT INVENTORS | This data is not available for free |
| PATENT ASSIGNEE | This data is not available for free |
| PATENT FILE DATE | 12.03.99 |
| PATENT FOREIGN APPLICATION PRIORITY DATA | This data is not available for free |
| PATENT REFERENCES CITED |
Database WPI, Section CH, Week 9404, Derwent Publications Ltd., London, GB; Class A26, AN 94-031872, XP002064514 & JP 05 339 373 A (Hitachi Chem Co Ltd), Dec. 21, 1993 *Zusammenfassung*. Chemical Abstracts, vol. 66, No. 18, May 1, 1967, Columbus, Ohio, US; Abstract No. 76462, Novikov, S.N. et al: "Photopolymerization of Monomers Forming Charge Transfer Complexes With Each Other" XP002064513 *Zusammenfassung*. C.G. Roffey, Photopolymerization of Surface Coatings, John Wiley & Sons, pp. 74-75 and 117-118, 1982. |
| PATENT PARENT CASE TEXT | This data is not available for free |
| PATENT CLAIMS |
We claim: 1. A compound having two or more 2,3-dihydrofuran groups. 2. A compound as claimed in claim 1, obtained by reacting hydroxy-functionalized 2,3-dihydrofurans with polyfunctional carboxylic acids, isocyanates, epoxides, glycidyl ethers and/or chloroformates. 3. A compound as claimed in claim 1, obtained by reacting carboxy-functionalized 2,3-dihydrofurans with polyfunctional alcohols, amines, epoxides, glycidyl ethers and/or hydrazines. 4. A compound as claimed in claim 1, obtained by etherifying 3-hydroxymethyl-2,3-dihydrofuran with halosubstituted hydrocarbons. 5. The compound as claimed in claim 1, and having one of the following formulae IIa, IIb, IIIa, or IIIb: ##STR33## an aromatic or aliphatic hydrocarbon radical of 1-20 carbons with or without one or more carbonyl or ether groups, which may be substituted by one or more hydroxyls, or are SiR'.sub.3, wherein R' is H or an organic radical of 1-20 carbons, R.sup.3 is H, C.sub.1 -C.sub.20 -alkyl or C.sub.1 -C.sub.20 -alkoxy, R.sup.4 is H, C.sub.1 -C.sub.20 -alkyl or C.sub.5 -C.sub.20 -aryl, -aralkyl or -alkaryl, or C.sub.1 -C.sub.20 -hydroxyalkyl, except that one of R.sub.1 -R.sub.4 is replaced by X in formulae IIa or IIIa, or replaced by Z in formulae IIb or IIIb, X is a single bond or a divalent group selected from the group consisting of ##STR34## Z is a single bond, C.sub.1 -C.sub.10 -alkylene or phenylene, n is 2-20, and R.sup.5 is a polyvalent hydrocarbon radical of 1-20 carbon atoms, with or without ether or ester groups. -------------------------------------------------------------------------------- |
| PATENT DESCRIPTION |
The present invention relates to a process for producing coatings and moldings by radiation curing. The radiation curing of free-radically or cationically polymerizable compounds is widely known. The radiation curing of acrylate compounds has acquired particular industrial importance; with acrylate compounds, however, there is the fundamental problem that the photopolymerization is inhibited by oxygen. Since with cationic photopolymerization the problem of oxygen inhibition does not occur, cationically polymerizable compounds might be one alternative to the free-radically polymerizable compounds. What is required, however, is a curing rate comparable with that of the free-radically polymerizable compounds, especially the acrylate compounds, with performance properties of the resulting coatings or moldings which are where possible just as good as those obtained with said free-radically polymerizable compounds. EP-A-123 912 describes dihydropyrans as cationically polymerizable cyclic vinyl ethers for radiation curing. However, the curing rate, ie. the reactivity in the course of radiation curing, is completely inadequate. Dihydrofurans and their thermal, cationic polymerization are known per se, for example from Polymer Bulletin 28 (1992) 117-122. It is an object of the present invention, therefore, to provide a process for producing coatings or moldings by radiation curing, where little or no oxygen inhibition occurs, the reactivity of the compounds employed is as high as possible, and the performance properties of the resulting coatings and moldings are satisfactory. We have found that this object is achieved by a process for producing coatings or moldings by radiation curing, which comprises using high-energy light to irradiate radiation-curable compositions containing 1 to 100% by weight, based on the total amount of cationically and, if desired, free-radically polymerizable compounds, of compounds A) containing at least one cationically polymerizable 2,3-dihydrofuran group. We have also found radiation-curable compositions suitable for such a process. The compositions A) are preferably compounds containing 1-6 cationically polymerizable 2,3-dihydrofuran group. The molecular weight of the compounds A) is preferably below 5000 g/mol, particularly preferably below 1000 g/mol. Compounds A), of relatively high molecular weight, can be obtained in particular by attaching 2,3-dihydrofuran or derivatives thereof to polymers by means of polymer-analogous reactions. Particularly suitable compounds A include those containing at least one of the following groups: ##STR1## in which R' is H, an organic radical of 1-20 carbons, in particular a C.sub.1 -C.sub.20 aliphatic radical or C.sub.5 -C.sub.20 -aryl, -alkaryl or -aralkyl. Examples of suitable compounds A) having a dihydrofuran group are those of the formula (I) ##STR2## where, independently, R.sup.1 and R.sup.2 are H, C--OR' (R'=H, organic radical of 1-20 carbons, especially a C.sub.1 -C.sub.20 -aliphatic radical or C.sub.5 -C.sub.20 -aryl, -alkaryl or -aralkyl), ##STR3## an aromatic or aliphatic hydrocarbon radical of 1-20 carbons with or without one or more carbonyl or ether groups, which may be substituted by one or more hydroxyls, or are SiR'.sub.3, R.sup.3 is H, C.sub.1 -C.sub.20 -alkyl or C.sub.1 -C.sub.20 -alkoxy, R.sup.4 is H, C.sub.1 -C.sub.20 -alkyl or C.sub.5 -C.sub.20 -aryl, -aralkyl or -alkaryl, or C.sub.1 -C.sub.20 -hydroxyalkyl, or R.sup.3 and R.sup.4, or R.sup.1 and R.sup.2, each together as pairs, form a ring comprising a total of 4-5 carbons (including ring atoms of the dihydrofuran parent structure) which may also include an ether group and may be substituted by hydroxyl, carboxyl or amino. Preferred compounds of the formula I are those where ##STR4## C.sub.1 -C.sub.20 -hydroxyalkyl, C.sub.1 -C.sub.20 -alkyl or C.sub.5 -C.sub.10 -aryl, R.sup.3 is H, and R.sup.4 is H, C.sub.1 -C.sub.20 -alkyl or C.sub.1 -C.sub.20 -hydroxyalkyl. With particular preference, R.sup.1, R.sup.3 and R.sup.4 are H and R.sup.2 is as defined above, and in particular is H, CH.sub.2 OH, C.sub.1 -C.sub.20 -alkyl or phenyl. Examples of compounds of the formula I are represented by the following structural formulae: ##STR5## Particular mention may also be made of compounds I of the formulae ##STR6## where R" is a hydrocarbon radical of up to 20 carbons, especially C.sub.1 -C.sub.10 -alkyl, phenyl or benzyl. Examples of suitable compounds A) having two or more 2,3-dihydrofuran groups are those of the formula ##STR7## where X is a single bond or a divalent group selected from: ##STR8## Z is a single bond, C.sub.1 -C.sub.10 -alkylene or phenylene. R.sup.1 -R.sup.4 and R' are as defined above but one of R.sup.1 -R.sup.4 is omitted (in compounds with two or more 2,3-dihydrofuran groups it is preferably R.sup.2 which is omitted) and is replaced by Z or X. In the most simple case, for example, X and Z are a single bond, R.sup.1, R.sup.3 and R.sup.4 are H and R.sup.2 is omitted, to give the following structural formula: ##STR9## Other suitable compounds having two or more 2,3-dihydrofuran groups are those of the formula ##STR10## where R.sup.1, R.sup.2, R.sup.3, R.sup.4 and X and Z are as defined above, one of R.sup.1 -R.sup.4 is omitted and is replaced by the bond to X or Z, n is 2-20, preferably 2-6, particularly preferably 2 or 3, and R.sup.5, correspondingly, is a polyvalent hydrocarbon radical of 1-20 carbon atoms, especially C.sub.1 -C.sub.20 -alkyl or C.sub.5 -C.sub.20 -aryl, alkaryl or aralkyl with or without ether or ester groups. Compounds having 2 or more 2,3-dihydrofuran parent structures can be obtained, for example, by reacting hydroxy-functionalized 2,3-dihydrofurans with polyfunctional carboxylic acids, isocyanates, epoxides, glycidyl ethers and/or chloroformates or by reacting carboxy-functionalized 2,3-dihydrofurans with polyfunctional alcohols, amines, epoxides, glycidyl ethers and/or hydrazines. Preferred compounds of the formula IIIa where n=2 are ##STR11## obtainable, for example, by esterifying the corresponding hydroxyl-substituted 2,3-dihydrofurans with dicarboxylic acids, dicarboxylic esters or dicarbonyl chlorides, ##STR12## obtainable by esterifying the corresponding carboxyl-substituted 2,3-dihydrofurans with diols, ##STR13## obtainable by reacting the corresponding hydroxyl-substituted 2,3-dihydrofurans with diisocyanates, ##STR14## obtainable by reacting the corresponding hydroxyl-substituted 2,3-dihydrofurans with chloroformic esters of diols, ##STR15## obtainable by reacting the corresponding carboxyl-substituted 2,3-dihydrofuran derivatives with diamine compounds, ##STR16## obtainable by reacting the corresponding hydroxyl-substituted 2,3-dihydrofurans with polyfunctional glycidyl ethers, ##STR17## obtainable by reacting the corresponding carboxyl-substituted 2,3-dihydrofurans with polyfunctional glycidyl ethers, ##STR18## where R'"=R'obtainable by reacting the corresponding hydroxyl-substituted 2,3-dihydrofurans with polyfunctional epoxides, and ##STR19## obtainable by reacting the corresponding carboxyl-substituted 2,3-dihydrofurans with polyfunctional epoxides. A preferred compound of the formula IIIb is: ##STR20## Preferred compounds of the formulae III where n is >2 are: ##STR21## obtainable by reacting, for example, glycerol, trimethylolethane or trimethylolpropane with ##STR22## obtainable by reacting pentaerythritol with ##STR23## n=6: esterification product of sorbitol (Chemical Abstracts Registry Number 50-70-4) or dipentaerythritol with ##STR24## n>6: esterification product of polyvinyl alcohol with ##STR25## In the above formulae IIa, IIb, IIIa and IIIb, the radical R.sup.2 is preferably omitted and replaced by the bond to X or Z. ##STR26## Z is preferably a single bond (and is therefore omitted) or is a methylene group. ##STR27## The synthesis of 2,3-dihydrofuran or its derivatives where n=1 is known to the skilled worker and is described, for example, in P. Dimroth, H. Pasedach, Angew. Chemie 72 (1960) 865 or in M. A. Gianturco, P. Friedel, V. Flanagan, Tetrahedron Lett. 23 (1965) 1847. The radiation-curable compositions employed in the novel process contain 1-100% by weight, preferably 5-100% by weight, particularly preferably 10-100% by weight, and very particularly preferably 30-100% by weight, based on the cationically and, if present, free-radically polymerizable compounds, of compounds A). In particular, however, more than 50% by weight of the cationically and, if present, free-radically polymerizable compounds can be compounds A), or the polymerizable compounds may exclusively be compounds A). In addition to compounds A), examples of other suitable cationically polymerizable compounds are, in particular, linear or cyclic vinyl ethers, such as vinyl methyl ether, vinyl ethyl ether, vinyl propyl ether, vinyl isobutyl ether, vinyl octadecyl ether, vinyl cyclohexyl ether, and .alpha.-methylvinyl alkyl ethers. In addition to compounds A), other suitable cationically polymerizable compounds are epoxides, for example cyclopentene oxide, cyclohexene oxide, epoxidized polybutadiene, epoxidized soya oil, Degacure K 126 or glycidyl ethers, for example butanediol diglycidyl ether, hexanediol diglycidyl ether, eg. bisphenol A diglycidyl ether, and pentaerythritol diglycidyl ether. In addition, it is likewise possible to employ cationically polymerizable monomers, such as unsaturated aldehydes and ketones, dienes such as butadiene, aromatic vinyl compounds such as styrene, N-substituted vinylamines such as vinylcarbazole, or cyclic ethers such as tetrahydrofuran. In addition to cationically polymerizable compounds it is also possible to use, in addition, free-radically polymerizable compounds or both free-radically and cationically polymerizable compounds. Examples are aromatic vinyl compounds having up to 20 carbons, vinyl esters of carboxylic acids having up to 20 carbons and, in particular, (meth)acrylate compounds as described, for example, in R. Holman, U. V. and E. B. Curing Formulations for Printing Inks and Paints, London 1984. In addition to monoacrylates, for example C.sub.1 -C.sub.20 -alkyl (meth)acrylates, compounds having two or more (meth)acrylic groups are also particularly suitable. Examples which may be mentioned are trimethylolpropane triacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, hexanediol diacrylate or polyester, polyether, epoxy or urethane acrylates. Preference is given to (meth)acrylate compounds with 2-6, especially 2-4, (meth)acrylic groups. The molecular weight of the acrylate compounds is preferably below 5000 g/mol, particularly preferably below 3000 g/mol. Unsaturated polyesters are also suitable as free-radically polymerizable compounds. The content of free-radically polymerizable compounds in the radiation-curable compositions is preferably 0-99%, particularly preferably 0-70%, and, with very particular preference, 0-30%, based on the overall weight of the cationically and free-radically polymerizable compounds. The radiation-curable compositions preferably contain a photo-initiator for the photopolymerization. The total amount of photoinitiator is preferably 0.1-10%, particularly preferably 0.5-5%, based on the overall weight of the cationically and, if present, free-radically polymerizable compounds. Cationic photopolymerization photoinitiators, when irradiated with UV light, provide acids; examples of such initiators which may be mentioned are aryldiazonium, aryliodonium or arylsulfonium salts, disulfones, diazodisulfones, imidotriflates, and benzoin tosylates of the following structures: ##STR28## Further examples which may be mentioned are p-methoxybenzenediazonium hexafluorophosphate, benzenediazonium tetrafluoroborate, toluenediazonium tetrafluoroarsenate, diphenyliodonium hexafluoroarsenate, triphenylsulfonium hexafluorophosphate, benzenesulfonium hexafluorophosphate, toluenesulfonium hexafluorophosphate or Degacure KI85 (bis[4-diphenylsulfonio-phenyl] sulfide bishexafluorophosphate), isoquinolinium salts, phenylpyridinium salts or picolinium salts, for example N-ethoxyisoquinolinium hexafluorophosphate, N-ethoxy-4-phenylpyridinium hexafluorophosphate or N-ethoxy-2-picolinium hexafluorophosphate. Ferrocenium salts (eg. Irgacure 261 from Ciba) or titanocenes are also suitable. Where the radiation-curable compositions also contain free-radically polymerizable compounds, photoinitiators for free-radical photopolymerization are preferably also used in proportion to the content of these compounds. Also possible is the exclusive use of photoinitiators for free-radical polymerization, especially when the proportion of free-radically polymerizable compounds is more than 30% of the overall weight of the polymerizable compounds. Examples of suitable photoinitiators for free-radical polymerization are benzophenone and derivatives thereof, for example alkylbenzophenones, halomethylated benzophenones, Michler's ketone, and also benzoin and benzoin ethers such as ethyl benzoin ether; benzil ketals such as benzil dimethyl ketal, acetophenone derivatives such as, for example, 2-hydroxy-1-methylphenylpropan-1-one and hydroxycyclohexyl phenyl ketone; anthraquinone and its derivatives, such as methylanthraquinone, and, in particular, acylphosphine oxides, for example Lucirin TPO (2,4,6-trimethylbenzoyldiphenylphosphine oxide) and bisacylphosphine oxides. In order to produce coatings the radiation-curable compositions are applied to the substrates to be coated, which consist for example of wood, paper, plastic or metal or, in order to produce moldings, are introduced into the mold provided. These radiation-curable compositions may include the additives which are customary for the particular intended application. When used as coating compositions their additives may, for example, be leveling agents, reinforcing agents, pigments or fillers. Radiation curing is preferably carried out using UV light. Examples of suitable UV sources are those with a wavelength range of 240-400 nm and an output of 50-240 W/cm. With particular preference, the radiation-curable compositions are suitable for producing coatings on wood, plastic, paper and metal, being crosslinked, ie. cured, by means of electron beams or, following the addition of photoinitiators, by UV radiation, to give coatings which meet the requirements of protective or decorative coatings. The radiation-curable compositions are of high reactivity; in other words, their curing rate on radiation curing is high. The coatings or moldings obtained exhibit good performance properties. |
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