Double Metal Cyanide Catalyst Reducing High Molecular Weight Tail
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Solution Overview
Problem
Existing DMC catalysts produce significant high molecular weight tail impurities during polyoxyalkylene polyol production, which interfere with the properties of elastomers and foams, and previous attempts to reduce these impurities have resulted in reduced catalyst reactivity.
Innovation Solution
A novel double metal cyanide catalyst composition including a metal salt, metal cyanide salt, alkali metal salt of an oxyacid with a pKa of 3.5 or less, and an organic complexing ligand, with alkali metal present in the range of 0.4 to 10 wt%, and optionally functionalized polymers, which disrupts the polymerization site accessibility to reduce high molecular weight tail formation while maintaining reactivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional DMC catalysts are used to produce high molecular weight polyols, then catalyst reactivity is maintained, but high molecular weight tail impurities are generated
Solution Approach 1:
The patent modifies the catalyst composition by changing chemical parameters - specifically incorporating alkali metal salts of oxyacids with pKa ≤ 3.5 and controlling alkali metal content at 0.4-10 wt%. This chemical parameter change alters the catalyst's behavior to suppress high molecular weight tail formation while preserving reactivity
Solution Approach 2:
The patent creates a composite catalyst system combining conventional DMC components with alkali metal oxyacid salts. This composite approach integrates multiple functional elements: the base DMC catalyst provides reactivity while the alkali metal oxyacid salt components selectively suppress harmful polymerization pathways that create high molecular weight tails
2Object-generated harmful factors
If catalyst composition is modified to reduce high molecular weight tail, then impurity levels decrease, but catalyst reactivity is reduced
Solution Approach 1:
The patent optimizes the alkali metal content parameter within a specific range (0.4-10 wt%) and selects oxyacids with pKa ≤ 3.5. These parameter changes are critical because they represent the threshold values where the catalyst begins to suppress high molecular weight tail formation while maintaining sufficient reactivity for practical applications
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 novel catalyst effectively reduces high molecular weight tail impurities while maintaining high reactivity, producing polyols with improved properties for elastomers and foams without the need for increased catalyst amounts.
Implementation Method 1
A novel double metal cyanide catalyst composition including a metal salt, metal cyanide salt, alkali metal salt of an oxyacid with a pKa of 3.5 or less, and an organic complexing ligand, with alkali metal present in the range of 0.4 to 10 wt%, and optionally functionalized polymers, which disrupts the polymerization site accessibility to reduce high molecular weight tail formation while maintaining reactivity.
Data Source
AI summary
This invention relates to novel double metal cyanide catalysts and to a process for the production of these double metal cyanide catalysts. These DMC catalysts can be used to prepare polyoxyalkylene polyols which have low amounts of high molecular weight tail compared polyoxyalkylene polyols prepared from DMC catalysts of the prior art.