Spandex Polymer Segment Weight Engineering
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Solution Overview
Problem
Conventional spandex production methods are costly and unable to achieve high elongation and low set properties using lower molecular weight glycols, as they limit the molecular weight of the hard segment and restrict the engineering of soft and hard segment molecular weights.
Innovation Solution
The under-capping process and extended glycol process allow for the independent engineering of soft and hard segment molecular weights by controlling the capping ratio and adding additional diisocyanate, enabling the production of spandex fibers with high elongation and low set properties without increasing the hard segment molecular weight, using lower molecular weight glycols.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional spandex production methods are used with lower molecular weight glycols, then production cost is reduced, but the molecular weight of the hard segment is limited and high elongation/low set properties cannot be achieved
Solution Approach 1:
The invention divides the polymer structure into distinct soft segments and hard segments with independently controlled molecular weights. By using the under-capping process, the soft segment (from glycol) and hard segment (from diisocyanate and chain extender) can be engineered separately, allowing the hard segment molecular weight to be increased beyond conventional limits while using lower molecular weight glycols for cost efficiency.
Solution Approach 2:
The invention changes the capping ratio parameter (ratio of diisocyanate to glycol) to below stoichiometric levels, creating under-capped prepolymers with isocyanate groups that subsequently react with additional diisocyanate. This parameter change enables independent control of soft and hard segment molecular weights, resolving the contradiction between hard segment molecular weight and production cost.
2Strength
If conventional prepolymer production processes are used, then the production process is simple, but the molecular weight of the hard segment is reduced when using lower molecular weight glycols
Solution Approach 1:
The under-capping process performs a preliminary reaction where glycol reacts with diisocyanate at a capping ratio below 1, creating isocyanate-terminated prepolymers before the final chain extension step. This preliminary action allows the hard segment molecular weight to be engineered independently of the glycol molecular weight, achieving higher hard segment molecular weights without increasing process complexity significantly.
3Ease of operation
If lower molecular weight glycols are used with conventional processes, then production cost is reduced, but high elongation and low set properties are not achievable
Solution Approach 1:
By changing the capping ratio parameter to below stoichiometric levels and controlling the soft to hard segment molecular weight ratio to greater than 12:1, the invention achieves fiber properties (high elongation, low set) that were previously only attainable with expensive high molecular weight glycols. The parameter changes enable lower molecular weight glycols to produce superior fiber properties.
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
This approach reduces production costs by using lower molecular weight glycols while achieving spandex fibers with unique properties such as high elongation, low set, and flat stretch/recovery, not attainable with conventional methods.
Implementation Method 1
adding a diisocyanate to a glycol at a capping ratio of less than 1.5 to produce an under-capped capped glycol
Implementation Method 2
adding additional diisocyanate to the capped glycol; and adding a chain extender to produce the polymer with engineered hard and soft segment molecular weights
Data Source
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AI summary
Polymer compositions and processes for extended glycols and under-capping glycols for production of polymer compositions with engineered hard and soft segment molecular weights are provided. Also provided are fibers and articles of manufacture such as fabrics and garments produced from these polymer compositions and processes.