Coating processes – Direct application of electrical – magnetic – wave – or... – Polymerization of coating utilizing direct application of...
Reexamination Certificate
2000-05-12
2001-06-05
Pianalto, Bernard (Department: 1762)
Coating processes
Direct application of electrical, magnetic, wave, or...
Polymerization of coating utilizing direct application of...
C427S387000, C427S558000, C427S559000, C427S595000
Reexamination Certificate
active
06242058
ABSTRACT:
FIELD OF THE INVENTION
This invention is a method for forming coatings from radiation curable compositions. More particularly, this invention relates to forming coatings from radiation curable compositions comprising an alkenyl ether functional polyisobutylene, a cationic photoinitiator, and optionally a free radical photoinitiator and/or an alkenyl ether compound which is free of isobutylene units on to components such as fiber optics where the component is at a temperature greater than about 50° C. and preferably at a temperature within a range of greater than 80° C. to about 120° C. The coating may be overcoated with an acrylate functional polymer.
BACKGROUND OF THE INVENTION
In order to protect their surface from damage caused by abrasion, optical fibers are typically coated with one or more polymers as they are drawn. Typically the fibers are drawn from a heated glass blank and coated by an in-line process before they come into contact with any solid surface. Prior to coating, however, the fiber must be allowed to cool. If the fiber's temperature is too high it cannot be coated in a stable fashion by conventional materials used for coating such fibers. Therefore in current practice tall draw towers, 25 meters or more in height, are employed in order to provide sufficient distance for convection cooling of the fiber. The speed at which this drawing and coating process can be run is limited by the need to cool the fiber to a temperature that does not cause detriment to the coating polymer(s) (See, for example, Polymers for High Technology, ACS Symposium Series: 346, Chapter 34, p. 410, American Chemical Society, Washington, DC (1987) and Levin et al., The Effects of Cure Temperature on The Reaction Kinetics and Elastic Modulus of a UV-Cured Acrylate System, Polym. Mater. Sci. Eng. (1995) 72:524-525). The present inventors have unexpectedly found that radiation curable compositions comprising an alkenyl ether functional polyisobutylene can be cured at higher temperatures than those compositions used in traditional commercial processes to coat such fibers, and therefore can result in faster throughput for processing equipment. In addition, it has been found that such coatings can readily be overcoated with acrylate functional polymers.
Polyisobutylenes containing functional groups which are radiation curable have been disclosed in the art. For example, T. P. Liao and J. P. Kennedy in
Polymer Bulletin
, V. 6, pp. 135-141 (1981) disclose acryl and methacryl telechelic polyisobutylenes having the formula CH
2
═C(R)—COO—PIB—OOC—C(R)═CH
2
where R is —H or CH
3
. These materials were prepared by reacting alpha, omega di-hydroxypolyisobutylene, HOCH
2
—PIB—CH
2
OH, and excess acryloyl or methacryloyl chloride. These prepolymers are disclosed as being useful in the synthesis of a variety of new composites containing a soft polyisobutylene segment.
J. P. Kennedy and B. Ivan in
Polymer Material Science and Engineering
, V. 58, p.866 (1988) disclose allyl telechelic linear and star-branched polyisobutylenes prepared by a convenient rapid one pot polymerization functionalization process. The polymerization step involved living polymerization of isobutylene by recently discovered mono- or multifunctional initiating systems (combinations of tert-ester and ether/Lewis acids) followed by electrophilic functionalizations by allyltrimethylsilane in the presence of TiCl
4
. Characterization indicated quantitative end allylations. Subsequent quantitative derivations of the allyl termini yielded mono-, di-, and tri-functional hydroxyl- and epoxy-telechelic polyisobutylenes which could be cured to rubbery networks.
J. P. Kennedy and B. Ivan in the
Journal of polymer Science, Part A, Polymer Chemistry
, V. 28, p. 89 (1990) disclose mono-, di-ended linear, and three-arm star allyl telechelic polyisobutylenes which are prepared by a rapid economical one-pot polymerization-functionalization process. The process involved the living polymerization of isobutylene by mono-, di-, or tri-functional initiating systems, specifically by aliphatic and aromatic tert-ester and -ether/TiCl
4
combinations, followed by electrophilic functionalization of the living sites with allyltrimethylsilane. Quantitative derivations of the ally termini yielded mono-, di-, and tri-epoxy and -hydroxy-telechelic polyisobutylenes. It is further disclosed that strong rubbery networks were made by curing the epoxy-telechelic polyisobutylenes with triethylene tetramine and by reacting the hydroxy-telechelic polyisobutylenes with MDI.
J. P. Kennedy et al., in
Polymer bulletin
, V. 25, p. 633 (1991) disclose vinyl ether terminated polyisobutylene macromonomers. However, no mention was made regarding radiation curable compositions based on these macromonomers. It is known that radiation cured networks from non-telechelic chain end functional macromonomers possess poor physical properties.
N. A. Merrill, I. J. Gardner, and V. L. Hughes in RadTech North America Proceedings, V. 1, pp. 77-85 (1992) disclose conjugated diene functional polyisobutylenes which have a high reactivity to both ultraviolet and electron beam radiation. These conjugated diene functional polyisobutylenes, alone or in a formulation, are disclosed as being useful in preparing pressure sensitive adhesives.
In PCT Patent Publication No. WO 9104992 is disclosed a functionalized copolymer of isobutylene and a para-methylstyrene, wherein at least one type of functional group is attached to the para-methyl group of the para-methylstyrene, the copolymer having a substantially homogenous compositional distribution. The functionalized groups are exemplified by alkoxides, phenoxides, carboxylates, thiolates, thiopenolates, thioethers, thiocarboxylates, dithiocarboxylates, thioureas, dithiocarbamates, xanthanates, thiocyanates, silanes, halosilanes, malonates, cyanides, amides, amines, carbazoles, phthalimides, pyridine, maleimide, cyanates, and phosphines.
In PCT Patent Publication No. WO 9211295 is disclosed a radiation reactive functionalized polymer comprising an isoolefin having about 4 to about 7 carbon atoms and a para-alkylstyrene, wherein a radiation reactive functional group is attached to the para-alkyl group of the para-alkylstyrene, and discloses radiation curable pressure sensitive adhesives comprising the functionalized polymer and a tackifier. In WO'295, the radiation curable groups are disclosed as being groups such as thioxanthones, acrylates, aldehydes, ketones, and esters.
Saxena et al., U.S. Pat. No. 5,665,823, disclose a method for preparing an acrylic functional polyisobutylene polymer or copolymer, the method comprising reacting a polyisobutylene polymer or copolymer which contains at least one carbon-bonded silanol group in it molecule with a silane having both an acrylic-containing group and a silicon-bonded hydrolyzable group in its molecule.
Furthermore, radiation curable compositions which contain vinyl ether functional organosilicon compounds have also been described in the art. For example, Crivello in U.S. Pat. No. 4,617,238 discloses a photopolymerizable composition comprising (a) an organopolysiloxane having at least one Si-bonded vinyloxy functional group of the formula H
2
C═CH—O—G—, where G is alkylene (such as propylene) or alkylene interrupted by at least one divalent heteroradical selected from —O—, divalent phenylene, or substituted divalent phenylene, or combination of such heteroradicals, and (b) an onium salt catalyst. The '238 patent also describes a method wherein the vinyl ether group is introduced into the organopolysiloxane by addition (hydrosilylation) of compounds with an allyl and a vinyl ether group to an SiH group of the organopolysiloxane in the presence of a platinum catalyst. In the method of the '238 patent, only the allyl group is added to the SiH group while the vinyl ether group is preserved and thus only one vinyl ether group for each SiH group can be incorporated into the siloxane molecule at any given time.
European Patent Publication No. 0462389 teaches thermosetting organopo
Bahadur Maneesh
Suzuki Toshio
Dow Corning Corporation
Pianalto Bernard
Troy Timothy J.
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