Polyadipate Plastisol Seal Migration Control
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Solution Overview
Problem
The existing plastisol formulations used in metal capsules for food containers, particularly those containing fatty or oily foods, exceed the allowed migration limits due to the high lipophilicity and low molecular weight of plasticizers like ESBO, leading to contamination concerns that are not compatible with current health standards.
Innovation Solution
The use of polyadipates with higher molecular weight and lower lipophilicity, specifically non-end-capped polyesters of 1,2-propandiole, 1,3- and 1,4-butandiole, and polypropylene glycol with adipic acid, which are designed to minimize surface exposure and control migration within legal limits, replacing traditional plasticizers such as ESBO.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional plasticizers like ESBO are used in plastisol formulations, then the seal achieves good flexibility and adhesion properties, but the migration level exceeds allowed health standards due to high lipophilicity and low molecular weight
Solution Approach 1:
The patent changes the molecular parameters of the plasticizer by selecting polyadipates with molecular weight greater than 1000 g/mol and specific polyol structures (1,2-propandiole, 1,3-butandiole, 1,4-butandiole, polypropylene glycol). This parameter change reduces lipophilicity and migration while maintaining seal performance
Solution Approach 2:
The patent creates a composite plastisol formulation combining PVC resin with specific polyadipate plasticizers that have non-end-capped structures. This composite material achieves both low migration (<30 ppm) and adequate flexibility through the synergistic properties of the resin-plasticizer system
2Object-affected harmful factors
If plasticizers with higher molecular weight are used to reduce migration, then the migration level decreases below 30 ppm, but the flexibility and workability of the plastisol may be compromised
Solution Approach 1:
The patent optimizes the molecular weight parameter within a specific range (>1000 g/mol) and controls the polyol structure to balance migration reduction with maintenance of plasticizer flexibility. The non-end-capped structure provides adequate chain mobility for workability
Solution Approach 2:
The patent uses specific polyol structures (1,2-propandiole, 1,3-butandiole, 1,4-butandiole, polypropylene glycol) that provide localized flexibility in the plasticizer molecule, ensuring adequate plastisol workability even with higher molecular weight components
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 new plastisol formulation with polyadipates achieves migration levels below 30 ppm, adhering to regulatory standards, while maintaining the hermetic seal integrity and usability, even under heat and mechanical stress conditions.
Implementation Method 1
a viscous liquid (plastisol) which is in general applied by a pressurised pistol provided with a nozzle located above the annular recess of the capsule... The solid resin is generally constituted by PVC (polyvinyl chloride) which is plasticised... This insertion process (gelatinisation) occurs, reaching a certain temperature, and it is a decidedly a physical, not a chemical, phenomenon... it has to undergo a process of hot-gelatinisation, which is done in a belt furnace, where the capsules remain for about 90 seconds at temperatures of between 210°C and 220°C
Implementation Method 2
By plasticisation is meant a process by which a chemical component (the plasticiser) is stably inserted in the molecular structure of a polymer (the PVC in this case), weaking the cohesion forces existing between the molecular chains, and increasing their mobility
Data Source
AI summary
A composition of Plastisol material, destined for creating seals for closing capsules of food products, comprises following components: resin to at least 35%; plasticiser to at least 30%; stabiliser to at least 0.3%; filler to at least 1%; slip to at least 1% and lubricant to at least 1%. The plasticiser is a polyester, of 1,2-propandiole and/or 1,3- and/or 1,4 - butandiole and/or polypropylene glycol with adipic acid, in which ends of the polymer chains below 1000 Da are constituted, to at least 50% thereof, by oxydrilic groups (-OH), excluding cyclic components with a fraction of less than 20% of oligomers of the polyadipate having a molecular weight of below 1000 Da.