The technical principle of the dishwasher capsule water-soluble film is mainly based on the dissolution characteristics of water-soluble polymer materials. Its core lies in achieving the precise release of detergent in the washing environment through specific material and process design. The specific principle is as follows:
Material properties and dissolution mechanism
Water-soluble polymer materials: The core material of water-soluble membranes is usually polyvinyl alcohol (PVA) or its modified derivatives. These polymers have strong hydrophilicity, and their molecular chains are 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.
Dissolution control: 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.
Chemical modification: The introduction of anionic groups such as carboxyl and sulfonic acid groups can enhance the hydrophilicity of the membrane or adjust its pH sensitivity. 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.
Packaging process and structural design
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.
Environmental adaptability
Water temperature responsiveness: During the main washing stage of a dishwasher, the water temperature is typically 60 to 75 degrees Celsius, 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 to 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).
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