Radiation Curable Primary Coating for Optical Fiber
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Solution Overview
Problem
Current radiation curable coatings for optical fibers lack improved manufacturing and performance properties, particularly in the use of a combination of aromatic and aliphatic isocyanates for preparing oligomers, which is not disclosed in existing documents.
Innovation Solution
A radiation curable Primary Coating composition comprising a urethane acrylate oligomer reaction product of hydroxyethyl acrylate, aromatic and aliphatic isocyanates, a polyol, a catalyst, and an inhibitor, with specific molecular weight and thermal properties, and a process for coating optical fibers using this composition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a radiation curable coating composition is used for optical fiber primary coating, then the coating can be cured rapidly with good adhesion, but the manufacturing properties and performance properties are not improved
Solution Approach 1:
The patent changes the molecular weight parameter of the urethane acrylate oligomer to a specific range (4000-15000 g/mol) and adjusts the composition ratios of aromatic versus aliphatic isocyanates to achieve optimal balance between manufacturing ease and coating performance
Solution Approach 2:
The patent creates a composite coating system combining urethane acrylate oligomer with specific molecular weight, aromatic and aliphatic isocyanates, photoinitiator, and other components to achieve synergistic effects that improve both manufacturing properties and coating reliability
2Strength
If the oligomer molecular weight is increased to improve mechanical properties, then the coating strength increases, but the coating becomes harder to process and apply
Solution Approach 1:
The patent optimizes the oligomer molecular weight within a specific range (4000-15000 g/mol) to achieve the right balance between mechanical strength and processability, avoiding both too low (weak coating) and too high (difficult to apply) extremes
3Speed
If UV radiation is used to cure the coating, then the curing speed is fast and adhesion is good, but the manufacturing efficiency at high line speeds is limited
Solution Approach 1:
The patent modifies the photoinitiator system and oligomer composition to enable effective curing at high line speeds (750-2100 meters/minute), allowing the UV curing process to maintain high speed while improving overall manufacturing efficiency
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides a Primary Coating with enhanced mechanical properties, including a peak tan delta Tg of -25°C to -45°C and a modulus of 0.50 MPa to 1.2 MPa, and improved adhesion and durability after curing, suitable for optical fiber applications.
Implementation Method 1
These coatings are typically applied to the optical fiber in liquid form, and then exposed to radiation to effect curing. The type of radiation that may be used to cure the coatings should be that which is capable of initiating the polymerization of one or more radiation curable components of such coatings. Radiation suitable for curing such coatings is well know, and includes ultraviolet light (hereinafter 'UV')
Data Source
AI summary
Radiation curable coatings for use as a Primary Coating for optical fibers, optical fibers coated with said coatings and processes for coating optical fibers. The radiation curable Primary Coating composition of the instant claimed invention includes an oligomer, a diluent % monomer; a photoinitiator; an antioxidant; and an adhesion promoter; wherein said oligomer is the reaction product of: a hydroxyethyl acrylate; an aromatic isocyanate; an aliphatic isocyanate; a polyol; a catalyst; and an inhibitor, wherein said oligomer has a number average molecular weight of from at least about 4000 g/mol to less than or equal to about 15,000 g/mol; and wherein said catalyst is selected from the group consisting of dibutyl tin dilaurate; metal carboxylates, including, but not limited to: organobismuth catalysts such as bismuth neodecanoate; zinc neodecanoate; zirconium neodecanoate; zinc 2-ethylhexanoate; sulfonic acids, including but not limited to dodecylbenzene sulfonic acid, methane sulfonic acid; amino or organo-base catalysts, including, but not limited to: 1,2-dimethylimidazole and diazabicyclooctane; triphenyl phosphine; alkoxides of zirconium and titanium, including, but not limited to Zirconium butoxide and Titanium butoxide; and Ionic liquid phosphonium salts; and tetradecyl(trihexyl) phosphonium chloride; and wherein a cured film of said radiation curable Primary Coating composition has a peak tan delta Tg of from about -25°C to about -45°C and a modulus of from about 0.50 MPa to about 1.2 MPa.