Biodegradable Polyester Aqueous Dispersion via Transesterification
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Solution Overview
Problem
The production of aqueous dispersions of biodegradable polyesters is challenging due to their high melt flow index and hydrophobic nature, making it difficult to shear them into aqueous emulsifier or protective colloid solutions, and the presence of free emulsifiers can be disruptive in many applications.
Innovation Solution
The process involves transesterification of biodegradable polyesters with polyethylene glycols and PEO-PPO block copolymers, followed by dispersion in water without additional surface-active additives, using a transesterification catalyst and specific conditions to reduce melt viscosity and facilitate stable dispersion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If biodegradable polyester melt is sheared into aqueous emulsifier solution, then aqueous dispersion is formed, but the process is difficult or impossible due to high melt flow index and hydrophobic nature
Solution Approach 1:
The patent uses reactive diluents (glycols, polyols, carboxylic acids) as intermediaries that chemically react with the polyester to modify its properties. These intermediaries reduce the melt viscosity and improve water compatibility, enabling the hydrophobic polyester to be processed into aqueous dispersions without requiring traditional emulsifiers.
Solution Approach 2:
The patent changes the chemical and physical parameters of the polyester by reacting it with various agents to reduce molecular weight, modify functional groups, and adjust melt flow index. This transforms the original hydrophobic, high-viscosity polyester into a modified version with improved processability and water compatibility.
2Stability of the object's composition
If free emulsifier is present in the dispersion, then dispersion stability is improved, but it becomes disruptive for many applications
Solution Approach 1:
The modified polyester serves its own emulsification needs through the reactive groups introduced during modification. The polyester molecules themselves possess amphiphilic characteristics after reaction with glycols and carboxylic acids, eliminating the need for separate emulsifier additives and thus avoiding the harmful effects of free emulsifiers in the final product.
Solution Approach 2:
The patent combines the functions of the polyester matrix and the emulsifying agent into a single integrated molecular structure. The modified polyester molecules contain both hydrophobic segments (from the original polyester) and hydrophilic segments (from reactive diluents), creating an intrinsic emulsifying capability within the polymer chains themselves.
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 method allows for the creation of stable aqueous dispersions of biodegradable polyesters without the need for emulsifiers or protective colloids, enabling the production of high-quality binders for coatings, adhesives, and nonwovens with improved physical and mechanical properties.
Implementation Method 1
transesterification of a biodegradable polyester from the group consisting of polyhydroxybutyrate (PHB), polyhydroxybutyrate-co-valeriate (PHBV), polybutylene adipate terephthalate (PBAT), polybutylene succinate (PBS), polybutylene succinate-co-adipate (PBSA) and their mixtures with a polymer from the group of polyethylene glycols, the PEO-PPO block copolymers
Implementation Method 2
dispersing the melt of the product thus obtained in water
Data Source
AI summary
The invention relates to an aqueous dispersion of a biologically degradable polyester, which is obtained by transesterification of a biologically degradable polyester with a polymer from the group of polyethylene glycols, PEO-PPO block copolymers, polyethylene glycol ethers having an aliphatic, branched or unbranched polyol with 3 to 6 C atoms and 2 to 6 OH groups, optionally in the presence of an ethylenically unsaturated dicarboxylic acid or its anhydride and/or optionally in the presence of a multivalent alcohol, and dispersion in water of the melt of the product obtained in this way.