Powerful and pro table solutions for compound manufacturing can be found by using proprietary performance additives, productivity enhancing pre-dispersed chemicals, master-batch products, and color concentrates. An overview of the available additives and their forms follows.
Pre-weighed Materials. Critical compound components, such as the cure system, are often pre-weighed and provided by a third-party supplier. Low melt point bags are used and the unit is added directly into the internal mixer. When the multi-components are pre-blended on a large scale, improved uniformity can be expected.
Dust-suppressed powders. Commonly treated by wetting with an oil or plasticizer, dust-suppressed powders reduce dust. Fluid selection should be governed by the intended application.
Dust suppression reduces direct material contact, inhalation hazards and in-process material loss to dust collectors.
Encapsulations. Polymer encapsulated powder products are completely dust-free and do not cling to packaging or handling equipment. In-process losses are substantially reduced and the product form is “environmentally friendly.” Re-massing is eliminated. Properly handled, mixing times can be dramatically reduced and mill pan or internal mixer throat sweeps can be eliminated. The rapid incorporation of polymer-encapsulated powders has facilitated changes in mixing procedures and resultant cost savings.
Absorbed “Liquids” (Dry Liquid Powders). A low melting solid or viscous liquid is difficult to handle and mix. Often, the material must be heated to handle, creating a safety hazard. Adding liquids during mixing lubricates compounds and reduces shear input. However, they must be added slowly to maintain effective mixing. Benefits include improved handling, more accurate weighing and addition, reduced packaging losses, and improved mixing.
Partitioned “Solids.” Lower melt point solids, such as tackifing resins, are often supplied in drums. Due to their low melt point, the material is one large mass. To handle these materials, they must be broken or crushed into small particles that can be weighed and mixed. Partitioning agents are usually clay, precipitated silica or diatomaceous earth. The prime benefit of this form is improved handling which translates into reduced labor costs and decreased health and safety issues.
Polymer based Dispersions. The key factors that determine dispersion quality are the raw material quality, the dispersion formulation, processing equipment and mixing procedure. A polymer based binder system (continuous phase) should be of sufficient viscosity at processing temperature to ensure adequate shear input to attain good deagglomeration and uniform dispersion. Benefits obtained when powders are replaced with polymer-based dispersions include improved material handling, reduced mixing time, and improved product and process uniformity when a multi-component dispersion is used.
Paste Dispersions. Chemical or color paste dispersions are often used in very low viscosity compounds to achieve good dispersion and distributive mixing. The same constraints are present with paste dispersions as were noted for all previous systems. Dispersion quality should be specified to ensure adequate quality for the final application. Benefits include improved dispersion and faster distribution in low viscosity compounds, and improved uniformity with multi-component paste dispersions.
Color Concentrates. Color typically involves either dyes or pigments. Because of the migration or “bleed” issues with dyes, pigments are used almost exclusively in rubber compounding applications. Advantages of polymer-bound, dry colors include: consistent product color, reduced handling/ housekeeping, rapid incorporation with excellent dispersion, and improved pigment dispersion.
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