Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Compositions to be polymerized by wave energy wherein said...
Patent
1991-11-28
1993-07-20
McCamish, Marion E.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Compositions to be polymerized by wave energy wherein said...
525454, 525455, 428378, 4284231, 428426, C08F 250, C08F28304
Patent
active
052294331
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a liquid, radiation-curable coating composition for the coating of glass surfaces, which comprises
A) 56 to 89% by weight of at least one diethylenically unsaturated polyurethane optionally containing urea groups,
B) 3 to 30% by weight of at least one ethylenically unsaturated monomer,
C) 0.5 to 8% by weight of at least one photoinitiator and
D) 0.05 to 6% by weight of an alkoxysilane, 100% by weight in each case.
In addition, the present invention relates to a process for the coating of glass surfaces, in particular of optical glass fibers, using these radiation-curable coating compositions.
Optical glass fibers have been steadily gaining in importance in the communication sector as light conductors. For this purpose it is absolutely essential to protect the glass surface from humidity and wear. For this reason the glass fibers are coated, as soon as produced, by a protective paint film.
Thus, according to EP-A-114,982, for example, glass fibers are first provided with a coating of a buffer (primer) which is flexible but has low hardness and tenacity, followed by a radiation-curable topcoat of great hardness and tenacity The two-coat system is alleged to provide good protection for the glass fibers against mechanical stresses even at low temperatures The topcoat used in EP-B-114,982 consists of radiation-curable coating compositions based on a polyurethane having diethylenic terminal groups, a diethylenically unsaturated ester of a diglycidyl ether of a bisphenol and a monoethylenically unsaturated monomer, the glass transition temperature of the homopolymer produced from this monomer being above 55.degree. C.
However, coatings of this nature on glass fibers have the important drawback of poor adhesion to the glass surface. Adhesion is impaired even further especially by humidity, in some circumstances to such an extent that total loss of adhesion to the glass surface occurs. The problem of poor adhesion of coatings to glass surfaces is known. For this reason, in order to improve adhesion, organosilanes are often added to the coatings as adhesion promoters. Thus, according to EP-B-33,043, for example, organosilanes are added as adhesion promoters to radiation-curable coating compositions based on vinyl monomers and reactive polymers (no polyurethanes), the presence of a thiirane ring in the vinyl monomers or the polymers being an essential part of the invention. Examples of suitable compounds cited are .gamma.-aminopropyl-triethoxysilane, N,.beta.-aminoethyl-.gamma.-aminopropyltrimethoxy-silane and .gamma.-glycidyloxypropyltrimethoxysilane. The document makes no reference to the problem of loss of adhesion of coatings to glass fibers under humid conditions.
JP-PS-45,138/85 of 08.10.1985 (corresponds to JP-OS 42,244/80 of 25.03.80) also discloses the use of organosilanes as adhesion promoters in radiation-curable glass fiber coatings, polymers comprising azide groups being used as the film-forming component. Examples of suitable silanes cited are .gamma.-methacryloxypropyltri-methoxysilanes, .gamma.-aminopropyltrimethoxysilane and .gamma.-glycidyloxypropyltrimethoxysilane. However,incorporation of the azide groups in the polymers to increase the rate of curing is an essential part of the invention in JP-PS 45,138. This document likewise makes no reference to the problem of the effect of humidity on adhesion of coatings to glass fibers.
Furthermore, EP-A-149,741 discloses liquid, radiation-curable coatings for glass fibers which comprise, besides a radiation-curable, polyethylenically unsaturated polymeric compound, 0.5 to 5%, based on the coating composition, of a polyalkoxysilane. Suitable polyalkoxysilanes are those which comprise an organic substituent containing a single active amino or mercaptyl hydrogen also capable of reacting with the ethylenically unsaturated compounds in a Michael addition. An example of suitable silanes cited is .gamma.-mercaptopropyltrimethoxy-silane. EP-A-149,741 claims that only by using silanes of this type is it possible to improve adhesion
REFERENCES:
patent: 4092173 (1978-05-01), Novak et al.
patent: 4289672 (1981-09-01), Friederich et al.
patent: 4472019 (1984-09-01), Bishop et al.
patent: 4921880 (1990-05-01), Lee et al.
patent: 4964938 (1990-10-01), Bachmann et al.
Hintze-Bruning Horst
Schunck Stephan
BASF Lacke+Farben Aktiengesellschaft
Berman Susan
Marshall Paul L.
McCamish Marion E.
Werner Frank G.
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