Branched Cellulose Ether Rheology Modifier for Exterior Coatings
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Solution Overview
Problem
Traditional exterior coatings are prone to destruction and washout due to early rain exposure, leading to productivity losses and delays on construction sites, as they often require excessive mixing times and can be challenging to formulate with highly viscous cellulose ethers, which are difficult to source and process.
Innovation Solution
The use of branched cellulose ethers with chemically bound polyoxyalkylene branches, which enhance wettability and facilitate particle breakup, reducing the viscosity of the coating and improving its water resistance, allowing for earlier rain resistance and faster drying times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If highly viscous cellulose ethers (above 60,000 mPa·s) are used as rheology modifiers, then the coating achieves proper viscosity for application, but the dissolution rate becomes excessive and requires excessive mixing durations
Solution Approach 1:
The patent modifies the molecular structure of cellulose ether by introducing branched architecture with polyoxyalkylene side chains, changing the rheological parameters to achieve optimal viscosity while reducing dissolution time. The branched structure with specific molecular weight (10,000-80,000 mPa·s) and degree of substitution provides the right balance between thickening effect and dissolution rate.
Solution Approach 2:
The patent creates a composite cellulose ether structure combining main chain cellulose units with polyoxyalkylene side chains. This composite molecular architecture provides both the necessary viscosity for application and improved wetting/dissolution characteristics, resolving the contradiction between achieving proper viscosity and limiting mixing time.
2Stability of the object's composition
If conventional linear cellulose ether rheology modifiers are used, then the coating achieves sufficient thickening, but the formulation becomes difficult due to excessive viscosity and poor wetting
Solution Approach 1:
The patent employs composite cellulose ether molecules with branched architecture where polyoxyalkylene side chains are chemically bound to the cellulose main chain. This composite structure provides superior wetting of substrate particles and smoother formulation compared to linear analogues, while maintaining appropriate rheology response.
Solution Approach 2:
The patent introduces polyoxyalkylene side chains at specific locations on the cellulose main chain, creating local regions of enhanced hydrophilicity and wetting capability. This localized modification improves particle wetting and formulation smoothness without compromising the overall rheology-enhancing effect.
3Productivity
If traditional exterior coatings are applied without modified cellulose ethers, then the coating can be applied, but the coating is destroyed and washed off by early rain exposure
Solution Approach 1:
The patent incorporates modified cellulose ether rheology modifiers into the coating formulation before application, which preliminarily establishes a protective film structure that resists water washout. The branched cellulose ether creates a three-dimensional network that prevents water penetration and coating removal during early rain exposure.
Solution Approach 2:
The patent uses composite cellulose ether structures with branched architecture that create a more robust film matrix compared to conventional linear cellulose ethers. This composite structure provides enhanced mechanical strength and water resistance, preventing coating destruction during early rain exposure.
4Stability of the object's composition
If highly viscous cellulose ethers are used, then the coating achieves proper thickening, but the particles are difficult to disperse and cause coating deficiencies
Solution Approach 1:
The patent optimizes the molecular weight and degree of substitution parameters of the cellulose ether to achieve the right balance between viscosity and dispersibility. The branched structure with controlled molecular weight (10,000-80,000 mPa·s) provides sufficient thickening while maintaining adequate particle dispersion and coating uniformity.
Solution Approach 2:
The patent introduces hydrophilic polyoxyalkylene side chains that create local regions of enhanced wettability, improving the dispersion of cellulose ether particles and preventing coating deficiencies such as settling, compaction, and grit while maintaining overall viscosity.
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 branched cellulose ethers significantly improve the resistance to water washout and reduce the drying time of exterior coating compositions, enabling earlier rain resistance and smoother application processes, while minimizing the need for excessive mixing and sourcing challenges.
Implementation Method 1
The polyoxyalkylene branches facilitate the particle breakup and dissolution of the granular rheology modifier. Enhanced wetting of the branched cellulose ethers enables smoother formulations
Implementation Method 2
The modified cellulose ether contains chemically bound polyoxyalkylene branches which enhance the wettability of the granulated cellulose ether particles. The polyoxyalkylene branches facilitate the particle breakup and dissolution
Implementation Method 3
A branched cellulose ether is a cellulose ether that has been chemically modified using bis-epoxy polyethers crosslinking agents
Data Source
AI summary
An exterior coating composition and method of using said coating to coat an exterior surface, the composition comprising: an aqueous emulsion of acrylic polymer, and at least one branched cellulose ether, wherein the branched cellulose ether has a viscosity of at least 6000 mPa·s in a 1% wt. % aqueous solution with a shear rate of 2.55 s−1 at 20° C. and an active addition weight percentage of 0.1% to 2.0% of the exterior coating composition.