Biodegradable Film Plasticizer Mixture for Tear Strength and Migration Control
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Solution Overview
Problem
Current biodegradable bags made from polyphase compositions containing starch lack uniformity in mechanical properties, particularly tear resistance in both longitudinal and transverse directions, and suffer from issues like fume production, oily condensates, and plasticizer migration when used for food packaging.
Innovation Solution
A biodegradable composition comprising a hydrophobic polyester continuous phase and a vegetable origin polymer dispersed phase, plasticized with a mixture of diglycerol, triglycerol, and tetraglycerol, which provides high mechanical isotropy and reduced plasticizer migration, achieved through specific extrusion conditions and particle size control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional plasticizers like glycerine are used in biodegradable films, then the films show high plasticizer migration when in contact with water, but using alternative plasticizers causes build-up on film-producing heads and produces fumes and oily condensates
Solution Approach 1:
The invention changes the chemical parameters of the plasticizer by using a specific mixture of diglycerol (70-90 wt%), triglycerol (5-20 wt%), and tetraglycerol (0-5 wt%). This compositional parameter change provides a plasticizer system that exhibits both low migration tendency and high thermal stability, eliminating the trade-off between migration control and fume production. The specific ratio parameters are optimized to achieve flash points above 200°C while maintaining water solubility below 50% migration.
Solution Approach 2:
The invention creates a composite plasticizer system by combining multiple glycerol derivatives (diglycerol, triglycerol, tetraglycerol) in specific proportions. This composite approach allows the plasticizer mixture to exhibit synergistic properties: diglycerol provides good plasticizing efficiency, while triglycerol and tetraglycerol contribute to higher thermal stability and reduced volatility. The composite plasticizer system thus simultaneously addresses both migration and fume production issues.
2Stability of the object's composition
If biodegradable films are made with starch and conventional plasticizers, then the films show anisotropic tear strength, but achieving isotropy requires water-plasticized destructurized starch which reduces productivity and increases process irregularities
Solution Approach 1:
The invention changes the plasticizer parameter from water to a glycerol derivative mixture, which fundamentally alters the plasticization mechanism. This parameter change enables the starch to achieve both destructuration and isotropic tear strength without requiring the extreme processing conditions that reduce productivity. The glycerol derivative plasticizer provides more uniform plasticization at lower shear rates, maintaining high production speeds while achieving the desired mechanical isotropy.
3Ease of manufacture
If biodegradable bags are produced with conventional plasticizers, then the plasticizer builds up on film-producing heads requiring regular removal, but using alternative plasticizers increases plasticizer migration when in contact with food
Solution Approach 1:
The invention changes the volatility parameter of the plasticizer by selecting glycerol derivatives with higher molecular weights and corresponding higher flash points. This parameter change ensures that the plasticizer remains non-volatile at extrusion temperatures, preventing build-up on film-producing heads. Simultaneously, the water solubility parameter is controlled through the specific composition ratios, ensuring that migration to food contact surfaces is limited to below 50% of the applied plasticizer.
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 enables the production of films with high tear strength in both directions, reduced plasticizer migration, and improved processability, suitable for thick and thin films, including bags and wrappings that support heavy loads without deformation or fume issues, while maintaining biodegradability.
Implementation Method 1
the vegetable polymers are plasticised by mixtures of plasticisers comprising diglycerol, triglycerol and tetraglycerol
Implementation Method 2
a continuous phase comprising at least one hydrophobic polyester, at least one dispersed phase comprising at least one polymer of vegetable origin, in which the hydrophobic polyester of the continuous phase is incompatible with the polymer of vegetable origin
Implementation Method 3
the plasticizers according to the present invention show a much lower tendency to migrate when the biodegradable polyphasic composition according to the invention are submitted to migration tests with water
Data Source
AI summary
Polyphase biodegradable compositions having a good resistance to ageing comprising a continuous phase comprising at least one hydrophobic polyester and at least one dispersed phase of polymer of vegetable origin. The hydrophobic polyester constituting the continuous phase is incompatible with the polymer of vegetable origin. The compositions comprise a plasticiser comprising at least 75% of a mixture of diglycerol, triglycerol and tetraglycerol.