Low Molecular Weight Cellulose Mixed Esters for Low Viscosity Coatings
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Solution Overview
Problem
Conventional cellulose esters used in coating compositions increase viscosity, leading to the need for higher organic solvent levels, which is undesirable due to VOC concerns, and result in brittle films when molecular weight is not maintained during esterification and hydrolysis processes.
Innovation Solution
Development of low molecular weight cellulose mixed esters with high maximum degree of substitution, which are soluble in a wide range of organic solvents and compatible with various co-resins, allowing for high solids, low viscosity coating compositions without the drawbacks of conventional low molecular weight esters, such as brittle films.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional cellulose esters are used in coating compositions, then performance properties such as hardness, clarity, and flow are improved, but viscosity increases and organic solvent levels must be increased
Solution Approach 1:
The patent changes the molecular weight parameter of cellulose esters to low molecular weight (number average molecular weight of 1,000 to 10,000) while maintaining appropriate degree of substitution and hydroxyl content, thereby reducing viscosity while preserving performance properties in coating compositions
Solution Approach 2:
The patent uses mixed ester groups (combinations of different ester functionalities) on the cellulose backbone to create composite molecular structures that provide both low viscosity and excellent performance properties including hardness, clarity, and flow characteristics
2Quantity of substance
If low molecular weight cellulose esters are used, then viscosity is reduced and solubility is improved, but film brittleness increases
Solution Approach 1:
The patent carefully controls the degree of substitution (0.5 to 3.0) and hydroxyl content (0.1 to 2.0 mmol/g) parameters alongside molecular weight to achieve the optimal balance where low molecular weight provides low viscosity while sufficient hydroxyl groups maintain film flexibility and prevent brittleness
Solution Approach 2:
The patent distributes different ester groups and hydroxyl groups at specific locations on the cellulose molecule (degree of substitution at different positions) to create local functional zones that provide both low viscosity characteristics and film-forming flexibility where needed
3Adaptability or versatility
If high degree of substitution is achieved, then solubility and compatibility are improved, but molecular weight degradation occurs during esterification
Solution Approach 1:
The patent performs preliminary protection of cellulose hydroxyl groups or uses activated cellulose substrates before esterification to prevent degradation during the reaction, enabling high degree of substitution to be achieved while maintaining controlled molecular weight
Solution Approach 2:
The patent uses intermediary catalysts or reaction mediators that facilitate high degree of substitution esterification while protecting the cellulose backbone from degradation, allowing simultaneous achievement of high solubility/compatibility and molecular weight control
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 low molecular weight cellulose mixed esters provide performance characteristics comparable to conventional esters while minimizing viscosity and solvent use, offering improved solubility, compatibility, and melt stability, enabling the use as binder components and additives in coatings and ink formulations.
Implementation Method 1
Cellulose esters are valuable polymers that are useful in many plastic, film, coating, and fiber applications
Implementation Method 2
low molecular weight cellulose mixed esters that are useful in coating and ink compositions as low viscosity binder resins
Implementation Method 3
Cellulose esters (CEs) are typically synthesized by the reaction of cellulose with an anhydride or anhydrides corresponding to the desired ester group or groups
Implementation Method 4
Some of these ester groups can afterward be hydrolyzed to obtain a partially-esterified product
Implementation Method 5
hydroxyl group content (to facilitate crosslinking)
Data Source
Figure 1
AI summary
Cellulose mixed esters are disclosed having low molecular weights and low degrees of polymerization. These new cellulose mixed esters include cellulose acetate propionate and cellulose acetate butyrate. The esters exhibit solubility in a wide range of organic solvents with minimal viscosity increase, are compatible with a wide variety of resins, and are useful in coatings and inks compositions as binder resins and rheology modifiers.