Solution to Separation of Calcium Carbonate in Hot Melt Adhesive

Heavy calcium carbonate (CaCO3) in hot melt adhesive is a commonly used filler that can increase the hardness of colloids, improve their wear resistance and stability, and reduce costs. However, in the hot melt adhesive system, due to its high density, heavy calcium is prone to settling, leading to segregation, that is, the separation of heavy calcium particles from the colloid, which affects the uniformity of the product and the final bonding effect. To reduce or avoid the segregation of heavy calcium in hot melt adhesive, the following measures can be taken:

1. Surface treatment: Surface modification treatment of heavy calcium, such as using coupling agents (such as silane coupling agents) or fatty acid treatment, can improve the compatibility between heavy calcium and polymer matrix and reduce segregation.
2. Dispersant Usage: Add an appropriate dispersant to help disperse heavy calcium more evenly in the hot melt adhesive system, preventing agglomeration and settling..
3. Formula adjustment: Optimize the formula of hot melt adhesive, for example, by adjusting the ratio of resin, wax, and plasticizer to improve the overall fluidity of the system and reduce the settling of heavy calcium..
4. Processing technology control: Ensure sufficient mixing time and strength during the production process to achieve good dispersion effect..
5. Storage conditions: Reasonably control storage conditions, avoid prolonged standing, regularly stir or shake the container, especially before use, to redisperse heavy calcium that may have begun to separate..
6. Fine grained heavy calcium: Using finer particle size heavy calcium helps improve dispersion and reduce settling tendency.
7. Ultrasonic treatment: In some cases, using ultrasonic treatment can help better disperse fillers and reduce segregation..

When using heavy calcium as a filler in hot melt adhesive, it is important to choose a suitable dispersant to prevent the aggregation and segregation of the filler. Hot melt adhesive systems are usually heat sensitive and may experience high shear stress during use, so dispersants need to be able to stabilize the dispersion state of heavy calcium under such conditions. Here are some types of dispersants that may be used in hot melt adhesive systems:

1. Polyester wax: Polyester wax is a common dispersant for hot melt adhesives, which can reduce the friction between heavy calcium particles, thereby reducing agglomeration and providing stability at high temperatures..
2. Fatty acid esters: such as stearic acid esters or palmitic acid esters, these dispersants can adhere to the surface of heavy calcium, improve its compatibility with the polymer matrix, and reduce segregation.
3. Fatty acid amides: Dispersants such as stearic acid amides or oleic acid amides can also improve the compatibility between heavy calcium and polymers, reduce particle interactions, and avoid agglomeration..
4. Low molecular weight polyethylene wax: This type of dispersant can provide lubrication in hot melt adhesive, reduce the settling of heavy calcium particles, and enhance the fluidity and demolding properties of the system.
5. Metal soap dispersants: such as zinc soap or calcium soap, these dispersants can adsorb on the surface of heavy calcium, change its surface charge, and prevent particle aggregation..
6. Modified Silicone: Silicone modifiers can provide good interfacial stability and dispersion stability, especially at high temperatures..
7. Specialized filler modifier: Some manufacturers provide modifiers specifically designed for heavy calcium, which can chemically or physically bind to the surface of heavy calcium to improve its dispersibility and stability in hot melt adhesives..

When selecting a specific dispersant, it is necessary to consider the specific components of the hot melt adhesive (such as EVA, polyolefin, etc.), as well as the application environment of the hot melt adhesive (such as temperature, shear conditions, etc.). In addition, compatibility between dispersants and heavy calcium and other components should also be considered to ensure that dispersants can effectively function without affecting the overall performance of the hot melt adhesive.