Plastic and nonmetallic article shaping or treating: processes – Direct application of electrical or wave energy to work – Polymerizing – cross-linking – or curing
Patent
1998-09-22
2000-11-07
Berman, Susan W.
Plastic and nonmetallic article shaping or treating: processes
Direct application of electrical or wave energy to work
Polymerizing, cross-linking, or curing
264488, 522154, 522166, 522162, 522150, 522153, 528405, 528407, 528417, C08G 6514, C08G 6516, G03F 7038, C08F 246, C08F 814
Patent
active
061432334
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a polymer which can be crosslinked by high-energy radiation and contains from 0.05 to 50% by weight, based on the polymer, of 2,3-dihydrofuran groups or derivatives thereof, each calculated as 2,3-dihydrofuran, and to a process for preparing coatings and moldings by radiation curing.
The radiation curing of free-radically or cationically polymerizable compounds is generally known. The radiation curing of acrylates has acquired particular industrial importance. A fundamental problem with acrylates, however, is that photopolymerization is inhibited by oxygen.
Since the problem of oxygen inhibition does not occur with cationic photopolymerization, cationically polymerizable compounds are a possible alternative to their free-radically polymerizable counterparts. However, the curing rate and performance properties of the resulting coatings or moldings must be comparable with, and where possible at least as good as, those of the free-radically polymerizable compounds, especially the acrylates.
EP-A-123 912 describes dihydropyrans as cationically polymerizable, cyclic vinyl ethers for radiation curing. The curing rate, i.e. the reactivity during radiation curing, however, is still completely inadequate.
Dihydrofurans and their thermal, cationic polymerization per se are known, for example from Polymer Bulletin 28 (1992) 117-122.
The earlier but nonprior-published German Patent Application P 19539294.9 (OZ 46308) discloses the radiation curing of 2,3-dihydrofurans.
It is an object of the present invention, therefore, to provide a process for preparing coatings or moldings by radiation curing which is subject to little or no oxygen inhibition, where the compounds employed are of maximum reactivity and where the performance properties of the resulting coatings and moldings are satisfactory.
We have found that this object is achieved by the polymer defined at the outset.
The 2,3-dihydrofuran groups in the polymer can be polymerized cationically by means of high-energy radiation (without oxygen inhibition), resulting in an increase in molecular weight or in crosslinking of the polymer (in short, curing).
The novel polymer contains from 0.05 to 50% by weight, preferably from 0.05 to 20% by weight and, with particular preference, from 0.05 to 10% by weight, based on the total weight of the polymer, of 2,3-dihydrofuran groups or derivatives thereof, every dihydrofuran group and every derivative thereof being calculated as 2,3-dihydrofuran.
The dihydrofurans involved are preferably those of the formula ##STR1## where R.sup.1 -R.sup.4 independently are hydrogen or a hydrocarbon radical of 1 to 15 carbons and one of R.sup.1 -R.sup.4 is replaced by the bond to the polymer.
R.sup.1 -R.sup.4 are preferably hydrogen or C.sub.1 -C.sub.10 -alkyl, particularly preferably hydrogen. The bond with the polymer is preferably from the carbon of the R.sup.2 substituent, so that R.sup.2 is absent from the above formula.
The novel polymer is obtainable by reacting polymers containing functional groups (termed functional polymers for short) with 2,3-dihydrofuran derivatives containing at least one, preferably one or two but especially one, group which is reactive with the functional groups (termed reactive 2,3-dihydrofuran derivatives for short).
The functional polymers may for example contain acid groups, especially carboxyl, anhydride, especially carboxylic anhydride, epoxide, halo, especially carbonyl halide groups, hydroxyl, primary or secondary amino or isocyanato, which are capable of reaction with the reactive dihydrofuran derivatives.
The functional polymers are obtainable in particular by free-radical polymerization of ethylenically unsaturated compounds (monomers).
The functional polymer and thus the novel polymer as well are composed largely of monomers a), called principal monomers, which are selected from C.sub.1 -C.sub.20 -alkyl (meth)acrylates, vinyl esters of carboxylic acids containing up to 20 carbons, vinyl-aromatic compounds having up to 20 carbons, ethylenically unsaturated nitrites, vinyl halid
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Database WPI, Section CH, Week 9404, Derwent Publications Ltd., London, GB; Class A26, AN 94-031872; "Heat Resistant Photosensitive Material Useful As Insulating Material For Semiconductor Device", Dec. 21, 1993, (abstract).
Simmons, H.E. et al.; "Phototakification of Polymer Blends", J. Applied Polymer Science, vol. 52, 1994, pp. 727-735.
Nuyken O. and Aechtner S.; "Cationic Polymerization of Selected .alpha.- and .beta.-substituted Vinyl Ethers", Polymer Bulletin 26, 117-122 (1992).
Beck Erich
Haussling Lukas
Nuyken Oskar
Raether Roman-Benedikt
Reich Wolfgang
BASF - Aktiengesellschaft
Berman Susan W.
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