Cyanoacrylate Monomer Recovery via Depolymerisation
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Solution Overview
Problem
Existing methods for producing α-cyanoacrylates, such as poly(alkyl-α-cyanoacrylates) or poly(alcoxyalkyl-α-cyanoacrylates), face challenges in achieving high-yield and high-purity monomers with minimal liquid waste and without hazardous gases, particularly in reactor designs that are complex and unsuitable for small-scale production, especially for medical adhesives.
Innovation Solution
A depolymerisation process using a stabilization system comprising phosphorous pentoxide, hydroquinone, ortho-phosphoric acid, and para-toluenesulfonic acid in a simple one-condenser batch reactor, eliminating the need for high-boiling solvents and hazardous gases, allowing for controlled depolymerisation and high-purity alkyl or alcoxyalkyl-α-cyanoacrylates production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If conventional depolymerisation methods using high-boiling solvents like tricresyl phosphate are employed, then depolymerisation can be achieved, but significant amounts of liquid waste are generated and complex reactor designs are required
Solution Approach 1:
The invention extracts and eliminates the high-boiling solvent (tricresyl phosphate) from the depolymerisation system, achieving depolymerisation without any solvent. This removes the source of liquid waste and simplifies the reactor design by eliminating the need for complex solvent recovery and handling systems.
Solution Approach 2:
The invention uses catalytic amounts of phosphorous pentoxide and hydroquinone that can be easily removed or regenerated, replacing the large amounts of expensive, persistent high-boiling solvents that create long-term waste disposal problems.
2Object-affected harmful factors
If gaseous inhibitors like sulphur dioxide are used during depolymerisation, then polymerization of cyanoacrylate vapours is inhibited, but hazardous and corrosive gases must be handled
Solution Approach 1:
The invention converts the potentially harmful role of gaseous inhibitors into a beneficial system where phosphorous pentoxide and hydroquinone work together to inhibit polymerization through a different mechanism. The phosphorous pentoxide dehydrates hydroquinone to form phosgene-free protective species that prevent cyanoacrylate polymerization without requiring hazardous gases.
Solution Approach 2:
The invention introduces phosphorous pentoxide as an intermediary substance that mediates between the depolymerisation process and polymerization inhibition. It acts as a dehydrating agent that activates hydroquinone to form the active inhibiting species, replacing the direct use of hazardous gaseous inhibitors.
3Ease of manufacture
If formaldehyde gas or aqueous solution is used in the condensation stage, then cyanoacetate reacts to form poly(alkyl-α-cyanoacrylates), but complex handling and purification are required
Solution Approach 1:
The invention changes the physical state parameter of formaldehyde from gas or aqueous solution to solid paraformaldehyde. This parameter change simplifies handling (no gas handling equipment needed, easier storage) while maintaining the chemical reactivity required for condensation with cyanoacetate to form the polymer.
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 process achieves high-yield and high-purity alkyl or alcoxyalkyl-α-cyanoacrylates with reduced liquid waste and no hazardous gas usage, suitable for both technical and medical adhesive applications, and allows for versatile, simple reactor designs suitable for small- and medium-scale production.
Implementation Method 1
phosphorous pentoxide and hydroquinone (polymerization inhibitors for the liquid cyanoacrylate)
Implementation Method 2
continuous depolymerisation of poly(alkyl-α-cyanoacrylate) esters
Implementation Method 3
This mixture is then depolymerised by heating a thin layer of this mixture in vacuum to produce high-purity monomeric α-cyanoacrylate vapours
Implementation Method 4
The first stage involves a high temperature condenser operating at ca. 150°C that collects a fraction containing primarily 'dimers' of cyanoacrylate... Subsequently, the gaseous phase enters a low-temperature condenser, operating at -8°C, where the cyanoacrylate monomer is collected
Data Source
AI summary
This invention is related to the preparation of alkyl or alcoxyalkyl-a-cyanoacrylates in monomeric form by depolymerisation of the corresponding poly(alkyl-a-cyanoacrylates) or poly(alcoxyalkyl-a-cyanoacrylates) (PCA). The PCA's are obtained preferably by base-catalyzed condensation of a cyanoacetate with formaldehyde (or a polymer of the latter). According to the invention, the poly(alkyl-a-cyanoacrylate) or poly(alcoxyalky-a-cyanoacrylate), the condensation product, is mixed with a depolymerisation system comprising phosphorus pentoxide P2O5, hydroquinone, ortho-phosphoric acid and para-toluenesulfonic acid. This process is realized in a batch reactor fitted with a condenser, heated at a temperature in the range of 100-300ºC, under a vacuum of 0.5-50 Torr (7.10-5 - 7.10-3 MPa) and gives rise to monomeric alkyl-a-cyanoacrylates or monomeric alcoxyalkyl-a-cyanoacrylates, being stable in both gaseous and liquid phase. After an additional purification by vacuum distillation, these cyanoacrylates can be used as fast setting technical or medical adhesives.