Biodegradable Flushable Film with Water-Dispersible Core
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Solution Overview
Problem
Current disposable absorbent articles, such as diapers and sanitary napkins, face challenges in being flushable and biodegradable while maintaining mechanical strength and preventing leakage, with existing solutions suffering from stickiness, poor mechanical properties, and high costs due to non-renewable synthetic polymers.
Innovation Solution
A biodegradable and flushable film comprising a water-dispersible core layer and a water-barrier skin layer, where the core layer constitutes 50-99% of the film and the skin layer 1-50%, using starch polymers and synthetic biodegradable polyesters to enhance renewability and reduce stickiness, while maintaining integrity during use and degrading in aqueous environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the backsheet materials are made very thin to reduce the overall bulk of the disposable absorbent article and reduce the likelihood of blockage of the toilet or sewage pipe, then the flushability and reduc tion of blockage risk are improved, but the mechanical strength and handling capability deteriorate
Solution Approach 1:
The patent employs a composite material system consisting of a water-soluble polymer matrix (such as polyvinyl alcohol) combined with water-insoluble biodegradable particles (such as polycaprolactone or starch). This composite structure allows the film to maintain mechanical integrity when dry through the polymer matrix, while the biodegradable particles enable disintegration in aqueous environments, thus resolving the contradiction between mechanical strength and flushability.
Solution Approach 2:
The patent utilizes parameter changes by exploiting the different responses of the polymer matrix and biodegradable particles to water. The polymer matrix maintains its structural properties in dry states providing mechanical strength, while both components undergo significant property changes when exposed to water - the polymer dissolves and the particles biodegrade, enabling flushability. This parameter-based differentiation resolves the contradiction between dry strength and wet disintegration.
2Reliability
If biodegradable polymers such as starch are used to enhance renewability and reduce environmental impact, then the environmental sustainability is improved, but the mechanical properties and processability deteriorate
Solution Approach 1:
The patent creates a composite material where biodegradable particles (starch, polycaprolactone) are dispersed within a water-soluble polymer matrix. The polymer matrix serves as a binder that provides processability and mechanical strength during manufacturing, while the biodegradable particles contribute to environmental sustainability. This composite approach allows the material to be manufactured using conventional processes while maintaining high biodegradability and renewability.
Solution Approach 2:
The water-soluble polymer matrix acts as an intermediary that facilitates the processing and handling of biodegradable particles. During manufacturing, the polymer provides a workable matrix that holds the particles together, enabling film formation and handling. After use, the polymer dissolves in water, releasing the biodegradable particles for complete degradation, thus the polymer serves as a temporary intermediary that enables manufacturing but disappears in the environment.
3Ease of manufacture
If synthetic biodegradable polymers are used to achieve melt processability, then the ease of manufacture is improved, but the renewability and environmental friendliness worsen
Solution Approach 1:
The patent uses a composite material system where synthetic biodegradable polymers (such as polycaprolactone) are combined with natural biodegradable materials (such as starch) and a water-soluble polymer matrix. The synthetic component provides melt processability for manufacturing, while the natural starch component and water-soluble matrix ensure high renewability and environmental compatibility. This composite approach balances manufacturability with sustainability.
Solution Approach 2:
The patent merges three different material types: water-soluble polymers (for flushability), synthetic biodegradable polymers (for processability), and natural biodegradable polymers like starch (for renewability). By combining these materials in a composite system, the patent achieves all desired properties - the synthetic component enables manufacturing, the natural component ensures renewability, and the water-soluble matrix provides flushability, thus resolving the contradiction between processability and renewability.
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 film effectively limits fluid flow during use and degrades in sewage systems, reducing environmental impact and maintaining mechanical strength, thus addressing the challenges of existing solutions.
Implementation Method 1
The water-dispersible layer comprises a water-soluble polymer
Implementation Method 2
the skin layer is formed from biodegradable polymers
Data Source
AI summary
A film that is both biodegradable and flushable, and yet can still act as a barrier to water or other fluids during use, is provided. More particularly, the film contains a water-dispersible core layer that helps the film to lose its integrity after being flushed, as well as a water-barrier skin layer that helps maintain the integrity of the film during use. The nature and relative concentration of the components in the water-barrier layer are selectively controlled to achieve a combination of different functions. That is, the majority of the polymers employed in the water-barrier layer are biodegradable polymers that can be degraded by microorganisms while in an aqueous environment (e.g., septic tank, water treatment facility, etc.). To even further enhance the overall renewability of the layer, a relatively high amount of the biodegradable polymers are starch polymers, which are also renewable. The starch polymers can also minimize the degree of stickiness in the film, which can sometimes result from certain types of synthetic polymers. Even at a high starch content, the present inventors have discovered that films may still be readily formed by using synthetic biodegradable polyesters in combination with the starch to facilitate melt processing.