Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Reexamination Certificate
1998-09-08
2001-10-30
Berman, Susan W. (Department: 1711)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
C522S075000, C522S081000, C522S095000, C522S117000, C522S129000, C522S153000, C385S144000, C385S123000, C385S145000
Reexamination Certificate
active
06309747
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a resin composition for coating optical fiber, and, more particularly, to a resin composition for coating optical fiber which, after curing, exhibits stable mechanical characteristics at high temperatures and no changes in color, and maintains durability for a long period of time.
2. Description of the Prior Art
Glass fiber used for optical fiber is very fragile and easily damaged. Therefore, coating the fiber with a resin which is curable by ultraviolet (UV) radiation is provided for protection and reinforcement.
Variations over time in mechanical characteristics, such as the Young's modulus and changes in the color of the UV curable resins must be small from the aspect of long-term reliability. This requires the content of noncurable components in the UV curable resin films to be as small as possible.
In order to improve the productivity of optical fiber manufacturing, the drawing speed of melted glass fiber material must be high. The high drawing speed, however, reduces the amount of radiation by UV light during the UV curable resin covering step, thereby leaving a greater amount of uncured components in the UV cured resin.
Therefore, along with the development of resins which satisfy various requirements in a variety of applications of these resins, the studies are ongoing for increasing the curing rate and curing degree. In addition, with regard to the reliability of the resins over a long period of time, various attempts for designing resin compositions having satisfactory properties such as heat resistance and weather resistance for preserving good outward appearance have been undertaken, including the investigations concerning the use of additives. No resin compositions have been developed, however, which are completely satisfactory.
Because UV curable urethane acrylate resins can satisfy a wide variety of requirements, they have been generally used for coating optical fiber. When used as a primary coating material, these UV curable urethane acrylate resins provide a film which contains only a very small amount of uncured components and which exhibits superb stability with little changes in the properties, while maintaining very soft properties. When used as a secondary coating material, they provide a film exhibiting tough properties and relatively hard. When they are used as matrix material, e.g. in ribbon structures, in addition to the characteristics required for the secondary coating material, they satisfy the requirements for good surface properties.
However, coating materials are desired which enable optical fibers to be usable under various conditions, occasionally, under very stringent conditions which have not been experienced by conventional optical fibers.
An object of the present invention is therefore to provide a liquid curable resin composition for optical fibers, which, while maintaining the superior properties and the high productivity of conventional urethane acrylate resins, exhibit excellent durability after curing.
In view of this situation, the present inventors have undertaken extensive studies and found that a resin composition containing a polymer having a specific type (meth)acryl group can produce a film which stably exhibits high mechanical properties at a high temperature with no change in color. The present inventors have found this resin composition to be useful for optical fiber coating.
SUMMARY OF THE INVENTION
Accordingly, the present invention provides a liquid curable resin composition for optical fibers comprising a polymer having a number average molecular weight of 5,000 or more and containing at least two types of recurring ethylenic units, of which one type has a substituent group containing an ethylenically unsaturated group and the second type is substituted by a group —COOR
3
(wherein R
3
is a hydrogen atom or a hydrocarbon group having 1-30 carbon atoms), an aryl group, a cyano group, an alkyl group having 1-10 carbon atoms or by one or more halogen atoms.
Preferably the ethylenically unsaturated group is a (meth)acryloyloxy group.
Preferably the polymer units are represented by the following formulas (1) and (2),
wherein R
1
and R
2
individually represent a hydrogen atom or a methyl group, X represents a group —COOR
3
(wherein R
3
is a hydrogen atom or a hydrocarbon group having 1-30 carbon atoms), an aryl group, a cyano group, a halogen atom, or an alkyl group having 1-10 carbon atoms, and Y represents a functional group containing a (meth)acryloyloxy group.
DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS
Examples of the hydrocarbon group R
3
having 1-30 carbon atoms in the above formulas are linear, branched, or cyclic alkyl, alkenyl, aralkyl, aromatic, or polycyclic hydrocarbons. Among these, linear, branched, or cyclic alkyl or alkenyl groups having 1-10 carbon atoms are preferred. Examples of preferred aryl groups are phenyl, halogenophenyl, methylphenyl, methoxyphenyl, and trialkylsilylphenyl. Of these, phenyl and methylphenyl are especially preferred. In case X is a halogen atom, examples of suitable halogen atoms are chlorine, fluorine, and bromine. When X is an alkyl group having 1-10 carbon atoms the alkylgroup can be linear, branched, or cyclic. Specific examples are methyl, ethyl, propyl, isopropyl, butyl, amyl, isobutyl, t-butyl, pentyl, isoamyl, hexyl, heptyl, octyl, isooctyl, 2-ethylhexyl, nonyl, decyl, isodecyl, and cyclohexyl.
The functional group Y containing a (meth)acryloyloxy group is preferably a group represented by the formula —A—B—OCOCR
4
═CH
2
, wherein A is —COO—, a phenyl group, or an alkylene group having 1-6 carbon atoms; B an alkylene group having 1-6 carbon atoms which may contain a hydroxy group; and R
4
represents a hydrogen atom or a methyl group.
In copolymer (a) the recurring unit (1) can consist of one group according to formula (1) or it may comprise two or more different types of units according to formula (1).
Component (a) can be prepared, for example, by copolymerizing a compound polymerizable by vinyl polymerization and a compound having a functional group which can later be used to introduce a (meth)acryloyloxy group and which is polymerizable by vinyl polymerization, and then introducing an acryl copolymer to the terminals or branches, preferably to the terminals, of the resulting copolymer.
The number average molecular weight of component (a) is 5,000 or more, preferably 5,000-50,000, and more preferably 10,000-40,000. If this number average molecular weight is smaller than 5,000, the viscosity of the resulting photo-curable resin composition is low so that coatability to optical fibers is impaired. If the molecular weight is greater than 50,000, the viscosity of the resulting photo-curable resin composition is too high so that coatability to optical fibers is also impaired.
Examples of the compounds polymerizable by vinyl polymerization are (meth)acrylate compounds, styrene compounds, acrylonitrile, and halogenated vinyl compounds.
Specific examples of (meth)acrylate compounds are methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isoamyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, lauryl (meth)acrylate, octadecyl (meth)acrylate, stearyl (meth)acrylate, benzyl (meth)acrylate, cyclohexyl (meth)acrylate, phenyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, tricyclodecanyl (meth)acrylate, isobornyl (meth)acrylate, and bornyl (meth)acrylate. Among these, preferred are methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isobornyl (meth)acrylate, and dicyclopentenyl (meth)acrylate.
As the styrene compounds, given are styrene, &agr;-methylstyre
Komiya Zen
Suwa Mitsuhito
Takasugi Yuji
Ukachi Takashi
Berman Susan W.
DSM N.V.
Pillsbury Madison & Sutro Intellectual Property Group
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