Polycarbonate Polyol Composition for Flexible, Strong Polyurethanes
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Solution Overview
Problem
Polycarbonate diols synthesized from 1,6-hexanediol exhibit high crystallinity, leading to polyurethanes with poor flexibility, elasticity, and texture, while those using oxyalkylene glycols lack sufficient mechanical strength and chemical resistance due to excessive crosslinking or low crosslinking amounts.
Innovation Solution
A polycarbonate polyol is synthesized using a specific oxyalkylene glycol and a branched alcohol, with controlled ratios of structural units from the branched alcohol and cyclic polycarbonate terminal groups to achieve a balance of flexibility, mechanical strength, and solvent resistance, preventing gelation during synthesis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If polycarbonate diols synthesized from 1,6-hexanediol are used, then mechanical strength is improved, but flexibility and elasticity deteriorate due to high crystallinity
Solution Approach 1:
The invention changes the chemical composition parameters of the polycarbonate diol by using specific oxyalkylene glycols (diethylene glycol, triethylene glycol, or tetraethylene glycol) instead of conventional 1,6-hexanediol. This compositional parameter change reduces crystallinity while maintaining mechanical strength, thereby improving flexibility and elasticity without sacrificing structural integrity.
Solution Approach 2:
The invention creates a composite polycarbonate diol structure by copolymerizing oxyalkylene glycol with small amounts of other diols (such as 1,6-hexanediol, 1,4-butanediol, or neopentyl glycol) and incorporating polyhydric alcohols (trimethylolpropane, pentaerythritol, or dipentaerythritol). This composite approach combines the flexibility benefits of oxyalkylene glycol with the mechanical strength contributions of the other components, achieving a balanced performance profile.
2Ease of operation
If oxyalkylene glycol is used as raw material, then flexibility is improved, but mechanical strength deteriorates due to insufficient crosslinking
Solution Approach 1:
The invention merges oxyalkylene glycol with polyhydric alcohols (trimethylolpropane, pentaerythritol, or dipentaerythritol) and other diols in a copolymerization system. This combination allows the oxyalkylene glycol to provide flexibility while the polyhydric alcohols contribute crosslinking structures that enhance mechanical strength, achieving a synergistic effect where both properties are improved simultaneously.
Solution Approach 2:
The invention carefully controls the compositional parameters by limiting oxyalkylene glycol content to 70-95 mass% and polyhydric alcohol content to 0.1-30 mass%, with specific constraints on the ratio of polyhydric alcohol to other diol (0.01-2.0 mass ratio). These parameter optimizations ensure sufficient crosslinking for mechanical strength while preserving the flexibility benefits of oxyalkylene glycol.
3Strength
If polyhydric alcohol is introduced to improve mechanical strength, then strength is improved, but flexibility deteriorates due to gelation
Solution Approach 1:
The invention applies partial action by using limited amounts of polyhydric alcohol (0.1-30 mass% of total polycarbonate polyol) rather than excessive quantities. This controlled partial incorporation provides enough crosslinking to improve mechanical strength while avoiding the gelation that would occur with higher concentrations, thereby preserving flexibility.
Solution Approach 2:
The invention optimizes the parameter of polyhydric alcohol content within a specific range (0.1-30 mass%) and controls the ratio of polyhydric alcohol to other diol (0.01-2.0 mass ratio). These parameter optimizations prevent gelation by maintaining the polyhydric alcohol content below the threshold that would cause excessive crosslinking, while still achieving improved mechanical strength.
4Strength
If crosslinking amount is increased to improve mechanical strength, then strength is improved, but solvent resistance deteriorates due to poor texture
Solution Approach 1:
The invention optimizes the crosslinking density by controlling polyhydric alcohol content (0.1-30 mass%) and the ratio of polyhydric alcohol to other diol (0.01-2.0 mass ratio). This parameter optimization achieves a balanced crosslinking structure that provides sufficient mechanical strength while maintaining adequate solvent resistance and appropriate material texture.
Solution Approach 2:
The invention creates a composite structure combining oxyalkylene glycol chains (providing flexibility and solvent resistance) with controlled crosslinking points from polyhydric alcohols (providing mechanical strength). This composite architecture ensures that crosslinking does not overly densify the structure, thereby preserving solvent resistance while achieving the desired mechanical 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
The resulting polyurethane exhibits high flexibility, mechanical strength, and excellent solvent resistance, suitable for applications like elastic fibers and artificial leathers with improved industrial productivity and performance.
Implementation Method 1
a polycarbonate polyol which is obtained by a polycondensation reaction using a polyhydric alcohol and a carbonate compound as raw materials
Data Source
AI summary
Provided is a polycarbonate polyol used as a raw material of a polyurethane that has an excellent balance of flexibility, mechanical strength and solvent resistance. The polycarbonate polyol includes structural units derived from a polyhydric alcohol and has a hydroxyl value of 20 to 450 mg KOH/g. The polyhydric alcohol includes: a diol (A) containing not less than 70% by weight of a specific oxyalkylene glycol (A1) ; and a trihydric to hexahydric branched alcohol (B) having 3 to 12 carbon atoms. In the polycarbonate polyol, structural units derived from the branched alcohol (B) is contained in an amount of 0.005 to 5.0% by mole in the structural units derived from the polyhydric alcohol. A ratio of a structural unit (X1) represented by the following Formula (X1) in the structural units derived from the branched alcohol (B) is not higher than 50% by mole.