Low Formaldehyde VAE Adhesive Dispersion via Redox Initiation
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Solution Overview
Problem
Existing adhesives for tobacco and food products face challenges in achieving very low formaldehyde content, as conventional emulsion polymerization processes often generate formaldehyde, which is harmful and requires stringent regulation compliance.
Innovation Solution
An aqueous dispersion of vinyl ester/ethylene copolymers is developed using a monomer mixture with a polyvinyl alcohol-based stabilizing system and a redox polymerization initiator system comprising a water-insoluble oxidizing agent and a sulfinic acid-based reducing agent, avoiding formaldehyde-generating co-monomers and ethylene oxide-containing emulsifiers to achieve a formaldehyde content of less than 5.0 ppmw.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional emulsion polymerization processes are used, then adhesives can be produced with good adhesion properties, but formaldehyde content increases to harmful levels
Solution Approach 1:
The patent extracts and removes formaldehyde-generating components from the adhesive system. Specifically, it eliminates self-crosslinking co-monomers (like N-methylolacrylamide) and reducing agents (like sodium formaldehyde sulfoxylate) that produce formaldehyde, while maintaining adhesion performance through alternative formulations using vinyl ester/ethylene copolymers with peroxide initiators
Solution Approach 2:
The patent changes the chemical parameters of the polymerization system by using vinyl ester/ethylene copolymers instead of conventional vinyl acetate copolymers, and by employing peroxide initiators instead of redox systems. These parameter changes result in adhesives with formaldehyde content below 5.0 ppmw while maintaining required adhesion properties
2Reliability
If formaldehyde-generating components are used in polymerization, then adhesive performance is improved, but compliance with regulatory requirements becomes difficult
Solution Approach 1:
The patent converts the harmful effect of formaldehyde generation into a benefit by using peroxide initiators that decompose to give clean initiation without formaldehyde byproducts. The self-crosslinking capability previously achieved through N-methylolacrylamide is replaced by alternative crosslinking mechanisms that do not generate formaldehyde, thus turning a harmful process into a beneficial one
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 solution results in adhesives with extremely low formaldehyde levels, suitable for tobacco and food applications, maintaining good adhesion and viscosity properties while ensuring compliance with stringent regulatory requirements.
Implementation Method 1
a free radical redox polymerization initiator system
Implementation Method 2
a polyvinyl alcohol-based stabilizing system
Data Source
AI summary
Disclosed are low-formaldehyde aqueous dispersions of vinyl ester/ethylene, e.g., vinyl acetate/ethylene (VAE), copolymers suitable for use in adhesives for applications such as tobacco or food products wherein only very low levels of formaldehyde are permitted. Such dispersions are prepared by emulsion copolymerization of a monomer mixture comprising a vinyl ester, ethylene, a stabilizing system comprising polyvinyl alcohol preferably having a degree of hydrolysis of at least 97 mole %, and a selected type of free radical redox polymerization initiator system. This selected redox initiator system comprises both a water-insoluble oxidizing agent and a sulfuric acid-based reducing agent. The monomer mixture which is polymerized is substantially free of co-monomers which yield free formaldehyde upon drying or curing of the dispersion and is also substantially free of ethylene oxide-containing emulsifiers. The aqueous dispersions resulting from polymerization of this monomer mixture has a solids content in weight percent and a Brookfield viscosity in millipascal-seconds such that the ratio of solids content to the natural logarithm of viscosity ranges from about 6.34 to about 8.25 wt %/ln(mPa·s). The dispersions herein also have a formaldehyde content of less than about 5.0 ppmw as determined by ISO-15173.