The technical principle of the water-soluble film for dishwasher capsules is mainly based on the combination of the dissolution characteristics of polymer materials and the packaging process. Its core lies in achieving the precise release of detergent in the washing environment through specific material and structural design. The following analysis is carried out from four dimensions: material properties, dissolution mechanism, packaging process and environmental adaptability:
1. Material properties: Selection of hydrophilic polymers
The core material of water-soluble membranes is usually polyvinyl alcohol (PVA) or its modified derivatives. These polymers have the following characteristics:
Strong hydrophilicity: The molecular chain is rich in hydroxyl groups (-OH), which can form hydrogen bonds with water molecules and rapidly absorb water, expand and dissolve in water at normal or high temperatures.
Controllable solubility: By adjusting the degree of polymerization, saponification or introducing copolymer monomers (such as vinyl alcohol-methacrylate copolymer), the dissolution rate and mechanical strength of the membrane can be controlled. For instance, PVA films with a high saponification degree dissolve more slowly in cold water and are suitable for scenarios that require moisture-proof storage. However, low saponification degree or modified membranes can disintegrate rapidly in hot water.
Biodegradability: Materials such as PVA can be decomposed by microorganisms in the natural environment, meeting environmental protection requirements.
2. Dissolution mechanism: Physical dispersion and chemical assistance
The dissolution process of water-soluble membranes mainly relies on physical actions, but their performance can be optimized through chemical modification:
Physical dissolution: After a membrane comes into contact with water, water molecules penetrate between the polymer chains, disrupting intermolecular forces (such as van der Waals forces and hydrogen bonds), leading to the disintegration of the membrane structure. The dissolution rate is affected by water temperature, water flow intensity and film thickness.
Chemical modification: By introducing anionic groups such as carboxyl and sulfonic acid groups, the hydrophilicity of the membrane can be enhanced or the pH sensitivity can be adjusted. For instance, PVA membranes containing carboxyl groups dissolve more quickly in alkaline washing solutions and are suitable for capsules that are paired with alkaline detergents.
Plasticizers and fillers: Adding plasticizers such as glycerin can lower the glass transition temperature of the film and enhance its flexibility. Adding fillers such as starch derivatives may regulate the dissolution rate or reduce the cost.
3. Packaging process: Multi-layer structure and precise molding
The encapsulation technology of water-soluble films needs to take into account both sealing and solubility. Common processes include:
Thermoforming and sealing: Two layers of water-soluble films are formed into a cavity by hot pressing or solvent bonding. After injecting detergent, it is sealed. The sealed area should have sufficient strength to prevent transportation damage and be easy to separate under the impact of water flow.
Multi-layer composite film: It is made by combining an inner barrier film (such as PVA) with an outer protective film (such as starch-based film). The outer layer delays water penetration, while the inner layer dissolves during washing. This structure can extend the shelf life of the capsules.
Microencapsulation technology: The active ingredient is encapsulated in tiny water-soluble vesicles and then encapsulated in capsules to achieve sustained-release or targeted release. For example, enzyme preparations can be prevented from being inactivated during storage through microencapsulation.
4. Environmental adaptability: Match the working conditions of the dishwasher
The design of water-soluble films needs to match the working parameters of the dishwasher:
Water temperature responsiveness: During the main washing stage of a dishwasher, the water temperature is typically 60-75℃, and the membrane material needs to dissolve rapidly at this temperature (e.g., within less than 1 minute). Some membrane materials, through cross-linking modification, can remain stable at low temperatures and accelerate dissolution at high temperatures.
Mechanical strength: The membrane needs to withstand the compression during transportation and the impact of water flow during washing, while avoiding residue. Toughness can be enhanced by adjusting the film thickness (typically 20-100μm) or adding nano-fillers (such as montmorillonite).
Residue control: After the membrane is completely dissolved, there should be no visible residue. This can be achieved by optimizing the molecular weight distribution or adding water-soluble additives (such as polyethylene glycol).
Technical Challenges and Future directions
Dissolution rate control: It is necessary to balance storage stability and washing efficiency to avoid premature dissolution or residue.
Cost optimization: Materials such as PVA are relatively expensive, and the development of low-cost alternatives like starch-based and alginate is a trend.
Function integration: Research on intelligent films such as light response and pH response to achieve on-demand release or zonal dissolution.
Through material design, process improvement and performance regulation, water-soluble film technology can achieve efficient encapsulation and precise release of detergents, promoting the development of dishwasher capsules towards a more convenient and environmentally friendly direction.
0aucj4