Self-coalescing latex with low molecular weight skin
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Solution Overview
Problem
Conventional latex paints require external coalescing agents to achieve suitable film formation at ambient temperatures, which can lead to compatibility issues, flammability, and environmental concerns due to volatile organic compounds (VOCs), while attempts to eliminate these agents often compromise paint properties such as film hardness and resistance.
Innovation Solution
A self-coalescing latex is developed through a sequential emulsion polymerization process that introduces a chain transfer agent during polymerization, creating a low molecular weight skin that acts as a plasticizer, eliminating the need for separate coalescing agents and reducing VOC content, while maintaining or enhancing paint properties like block and stain resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If external coalescing agents are added to conventional latex paints to achieve suitable film formation at ambient temperatures, then film formation capability is improved, but compatibility issues, flammability, and VOC-related environmental concerns arise
Solution Approach 1:
The latex polymer itself performs the coalescing function through self-coalescence. The patent modifies the polymer structure during emulsion polymerization to include segments with lower glass transition temperatures that enable the polymer to coalesce with itself at ambient temperatures without requiring external coalescing agents, thereby eliminating VOC emissions and flammability concerns
Solution Approach 2:
The patent changes the molecular structure parameters of the latex polymer by controlling the glass transition temperature (Tg) of different polymer segments. By creating a bimodal or multimodal Tg distribution through specific monomer composition and polymerization conditions, the polymer achieves optimal coalescence properties at ambient temperatures
2Object-generated harmful factors
If attempts are made to eliminate external coalescing agents from latex paint formulations, then VOC content is reduced, but paint properties such as film hardness and resistance are compromised
Solution Approach 1:
The patent divides the polymer structure into distinct functional segments: hard segments providing mechanical strength, hardness, and resistance properties, and soft segments providing flexibility and coalescence capability. This segmentation allows the polymer to achieve both low VOC content and maintained film properties through internal structural design rather than external additives
Solution Approach 2:
The patent creates a composite polymer structure combining different monomer units with complementary properties within a single latex particle. This internal composite structure integrates the functions of both hard and soft polymers, eliminating the need for separate coalescing agents while maintaining film performance
3Reliability
If soft polymers with low glass transition temperature are used to improve film formation, then film formation properties are enhanced, but the resulting film becomes tacky and has poor mechanical properties
Solution Approach 1:
The patent applies local quality by creating specific regions within the polymer structure that have different Tg values. The soft segments (low Tg) are localized to provide coalescence and film formation, while hard segments (high Tg) are distributed to provide mechanical strength, preventing the entire film from being tacky while maintaining good film formation
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 self-coalescing latex achieves film formation at ambient temperatures without external coalescing agents, reducing VOCs, and enhances paint properties like block and stain resistance, providing a cost-effective and environmentally friendly solution for latex paint compositions.
Implementation Method 1
introducing a substantial amount of chain transfer agent in the final moments of polymerization. This generates a low molecular weight soft polymer portion of the self-coalescing latex that acts as a thin plasticizer
Implementation Method 2
generates a low molecular weight soft polymer portion of the self-coalescing latex that acts as a thin plasticizer
Implementation Method 3
the coalescence of polymer chains between the residual particles leading to a fully developed coating/film
Data Source
AI summary
The present invention relates to self-coalescing latexes that incorporate film fat ing polymers that are low molecular weight polymers that are compatible with the latex and act as thin plasticizers penetrating through the remainder of the latex particle and aiding in the coalescence of the remaining polymers. In a preferred embodiment, the self-coalescing latex is a sequentially polymerized polymer having at least a core, a shell and a skin. The film forming polymers are formed of monomers substantially the same as the monomers of the shell but having average weighted molecular weights substantially less than the polymers of the shell. The present invention also relates to the method of polymerizing the self-coalescing latex of the current invention, which largely results from the addition of a substantial amount of chain transfer agent to a remaining portion, about 15% or less, of the monomer pre-emulsion prior to polymerization. Lastly, the invention relates to paint compositions incorporating the self-coalescing latexes that are substantially free of coalescing agents or aids.