Biodegradable Injection Moulded Articles Heat Resistance Impact Strength
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Solution Overview
Problem
Existing injection molded articles made from biodegradable polymer mixtures, such as those containing polybutylene succinate (PBS) and polylactic acid (PLA), lack sufficient heat resistance and impact strength for applications like coffee capsules, lids for hot drinks, and microwave dishes.
Innovation Solution
A specific composition of biodegradable polyesters, including succinic acid, aliphatic-aromatic polyesters, and polylactic acid, with a mineral filler, optimized for injection molding, which provides a heat deflection temperature (HDT-B) of 80 to 105 °C and high Charpy impact strength, achieved through a controlled molecular weight and viscosity number, and the use of less toxic titanium catalysts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If filled biodegradable polymer mixtures containing PBS and PLA are used for injection molding, then the articles can be manufactured with biodegradability, but the heat resistance and impact strength are insufficient for hot food applications
Solution Approach 1:
The patent employs a composite material system consisting of four components: biodegradable polyester (PBS-based, 47-59 wt%), aliphatic-aromatic polyester (PBAT, 3-14 wt%), polylactic acid (PLA, 15-24 wt%), and mineral filler (10-35 wt%, preferably talc). This multi-component composite achieves both high heat resistance (HDT-B: 80-105°C) and high impact strength (Charpy: >80 kJ/m²) simultaneously, resolving the contradiction between heat resistance and impact strength that plagues simpler biodegradable blends.
Solution Approach 2:
The patent optimizes specific parameter ranges for each component to achieve the desired balance. The biodegradable polyester content is maintained at 47-59 wt% to ensure biodegradability and baseline mechanical properties. The PBAT content is controlled at 3-14 wt% to enhance flexibility and impact strength without compromising heat resistance. The PLA content is limited to 15-24 wt% to maintain rigidity and heat resistance. The mineral filler content is optimized at 10-35 wt% to boost both heat resistance and impact strength. These precise parameter ranges resolve the contradiction by finding the optimal balance point.
2Temperature
If higher amounts of rigid polymer PLA are added to improve heat resistance, then the HDT-B temperature increases, but the impact strength decreases
Solution Approach 1:
The patent assigns different functional roles to different components based on their local qualities. PLA (15-24 wt%) provides local rigidity and heat resistance in the composite structure. PBAT (3-14 wt%) provides local flexibility and impact absorption. The mineral filler (10-35 wt%) provides local reinforcement and heat resistance enhancement. This distribution of local qualities across different components allows the overall composite to achieve both high HDT-B temperature and high impact strength, rather than relying on excessive PLA which would compromise impact strength.
3Productivity
If conventional catalysts are used in polyester synthesis, then the polymerization process is efficient, but toxic residues remain in the final product
Solution Approach 1:
The patent changes the chemical parameter of the catalyst from conventional toxic options (tin, antimony, cobalt, lead catalysts) to titanium-based catalysts (such as tetra(isopropyl) orthotitanate and tetraisobutoxy titanate). This parameter change maintains polymerization efficiency while dramatically reducing catalyst toxicity. The titanium catalysts produce less toxic residues that are safer for environmental degradation and food contact applications, resolving the contradiction between productivity and harmful factors.
Data Source
AI summary
The present invention relates to an injection-moulded article having a DIN EN ISO 75-2:2004-09 HDT-B of 80 to 105°C, comprising: i) 47 to 59 wt%, relative to the total weight of components i to iv, of a biodegradable aliphatic polyester; ii) 3 to 14 wt%, relative to the total weight of components i to iv, of an aliphatic-aromatic polyester; iii) 15 to 24 wt%, relative to the total weight of components i to iv, of polylactic acid; iv) 10 to 35 wt%, relative to the total weight of components i to iv, of at least one mineral filler; for components i to iv in compounded form, the ratio of component i to component iii in the compound is 2.2 to 3.2 and the DIN EN 1133-1 (01.03.2012) MVR (190°C, 2.16 kg) of the compound is 8 to 50 cm3/10 min.