Hard Capsule Molding Using PHA-Starch Composite
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Solution Overview
Problem
Existing methods for producing hard capsules, particularly those using starch or gelatin, face challenges with dimensional stability over time due to hygroscopy and embrittlement, and gelatin-based processes have limitations related to production rate and design freedom.
Innovation Solution
A process involving a polymer composition comprising polyhydroxyalkanoate and starch-containing polymer, homogenized with thermal and mechanical energy, is used for injection molding or thermoforming to produce dimensionally stable moldings, including hard capsules.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If thermoplastic starch is used for injection molding, then processability is improved, but dimensional stability deteriorates over time due to hygroscopy
Solution Approach 1:
The patent uses a composite material system consisting of starch-containing polymer (20-80 wt%), polyhydroxyalkanoate (30-70 wt%), and plasticizer (5-20 wt%). This composite approach combines the biodegradability and processability of starch with the dimensional stability and moisture resistance of polyhydroxyalkanoate, creating a material that achieves both ease of manufacture and long-term dimensional stability.
Solution Approach 2:
The patent optimizes the composition parameters within specific ranges: starch-containing polymer (20-80 wt%), polyhydroxyalkanoate (30-70 wt%), and plasticizer (5-20 wt%). By carefully controlling these parameter ranges and the molding process parameters (temperature, pressure, time), the material achieves optimal balance between processability and dimensional stability.
2Ease of manufacture
If large quantities of water are added to starch for processing, then processability is improved, but embrittlement occurs over time as water is released
Solution Approach 1:
The patent introduces polyhydroxyalkanoate as an intermediary substance that replaces the need for large quantities of water as plasticizer. This intermediary material provides the necessary processability during molding while preventing the embrittlement that occurs when water evaporates from the molded product.
Solution Approach 2:
The patent uses a small, controlled amount of plasticizer (5-20 wt%) in conjunction with polyhydroxyalkanoate to achieve processability, replacing the need for large quantities of water. This approach uses minimal temporary additives that do not cause long-term embrittlement.
3Productivity
If gelatin is used for injection molding, then production of hard capsules is achieved, but dimensional stability deteriorates over prolonged period and production rate is limited
Solution Approach 1:
The patent changes the material composition parameters by replacing gelatin with a starch-containing polymer and polyhydroxyalkanoate blend. This parameter change enables faster injection molding cycle times while maintaining or improving dimensional stability over prolonged periods.
4Ease of manufacture
If starch is processed with plasticizers to achieve thermoplastic processability, then ease of manufacture is improved, but dimensional stability deteriorates due to water absorption
Solution Approach 1:
The patent creates a composite material system where starch-containing polymer (20-80 wt%) provides thermoplastic processability when combined with polyhydroxyalkanoate (30-70 wt%) and plasticizer (5-20 wt%). The polyhydroxyalkanoate component specifically counteracts the hygroscopic nature of starch, maintaining dimensional stability while preserving ease of manufacture.
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 process results in hard capsules with improved dimensional stability over a prolonged period, avoiding the issues of hygroscopy and embrittlement, and allows for biodegradable and pharmacologically acceptable materials.
Implementation Method 1
homogenizing the polymer composition with use of thermal and/or mechanical energy
Implementation Method 2
homogenizing the polymer composition with use of thermal and/or mechanical energy
Implementation Method 3
molding a molding in the mold
Implementation Method 4
molding a molding in the mold
Data Source
AI summary
A process is presented and described for the production of moldings, comprising the steps of (a) providing a polymer composition comprising from 1 to 99% by weight of polyhydroxyalkanoate and from 1 to 99% by weight of starch-containing polymer; (b) homogenizing the polymer composition with use of thermal and/or mechanical energy; (c) introducing the polymer composition into a mold; (d) molding the molding in the mold; and (e) removing the molding from the mold. The process described is in particular suitable for the production of hard capsules.