Shoe Sole Manufacturing

By Process

Rubber Outsoles

McLube® has been a leading manufacturer of rubber mold release agents for decades. Our rubber release agents are currently used in the United States and around the world to produce durable, wear-resistant rubber outsoles for military-style footwear, safety shoes, and more.

McLube® rubber mold release agents have allowed our customers in the shoe sole industry to cut down on in-mold buildup, reducing the frequency of cleaning operations. McLube® rubber release agents protect molds from corrosion over time, particularly in humid climates, and prevent dirt and grime buildup during downtime/storage. Other benefits of McLube® rubber mold release technology include negligible transfer, limited in-mold buildup, and improved surface finish quality. Contact McLube® today to learn more about what we can do for your rubber shoe sole process.

Single-density Sole Casting

Single or “monodensity” soles are generally produced with open pour casting processes aided by an apply-every-cycle release agent. The frequency of release agent application in these processes can quickly lead to in-mold buildup and fouling, especially when applying wax-based coatings. McLube® has developed a line of coatings for the shoe sole industry that furnish an exceedingly thin releasing film on the substrate to limit in-mold buildup over time. Without rapid buildup, our customers experience fewer stoppages for cleaning and are able to cast more soles per shift. Our micro-thin release coatings will also preserve the finest mold details, improving tread pattern definition and allowing for more intricate lettering and graphics. McLube® mold release technology will not interfere with finishing steps or attachment to the upper shoe. Our line of release agents for single-density shoe soles includes water-based and solvent-based options with tailorable concentrations, slip coefficients, and gloss levels to suit individual process requirements. McLube® has also developed release agents for single-density sole casting that provide several releases per spray for some manufacturers. Contact us today for additional product information and samples.

Dual-density Sole Casting

Dual-density or “bi-density” shoe soles include an outsole and midsole that are bonded together inside the mold. A “dummy last” serves as a temporary top cover for casting the outsole and is removed before the midsole material is poured and cured over the outsole. McLube’s water-based and solvent-based release agents for dual-density soles are designed to provide effective release without interfering with midsole-outsole bonding or post-molding steps like painting and upper shoe attachment. These coatings are suitable for application to the mold surface as well as dummy lasts and versatile enough to release differing outsole and midsole compounds. Contact McLube® today and one of our local Technical Representatives will work with you to provide the ideal release agent for your dual-density process.

Injection Molded / Direct Attach Soles

Injection molding requires release agents that are capable of adhering to the surface of the mold while also providing sufficient slip to aid material flow throughout the entire cavity. If a release with poor surface adhesion is used, the material will push the coating around the mold, causing knit lines and ineffective release. A release agent with poor flow characteristics (high surface energy) can cause uneven sole thickness and even material starvation in complex areas of the mold cavity. Material starvation is particularly concerning for RIM shoe sole processes that involve complex tread patterns and graphics. While a certain degree of slip is necessary to aid material flow, too much slip will cause a release agent to have poorer surface adhesion.

McLube® understands the delicate balance between surface adhesion and material flow characteristics that is crucial to providing ideal release performance inside injection molds. Our release agents for shoe sole processes contain proprietary additives that allow our coatings to bond to the mold surface for unparalleled durability. McLube® will also tailor slip coefficients to create the optimal surface energy inside your mold to aid material flow without causing knit lines.

Direct attach processes account for most resin and elastomeric injection molding in the footwear industry. Reducing scrap and rejection rates is of particular concern in direct attach operations because the sole is bonded directly to the upper shoe during this process; if the sole does not release properly, the upper shoe is also wasted. McLube® will typically engineer a custom formulation for molders using direct attach processes to ensure soles are de-molded exactly as intended and scrap is kept to a minimum. Contact McLube® today and our experienced Technical Representatives and Formulation Chemists will help you develop the ideal coating for your process as well as guide you through testing and implementation.

Applications

Supported Materials

McLube® offers water and solvent-based release agents for many shoe sole materials, including natural and synthetic rubber, thermoplastic rubber (TRP), and polyurethane (polyester and polyether PU systems), ethyl vinyl acetate (EVA), PVC, BPU, and acrylonitrile butadiene styrene (ABS).

Shoe sole manufacturers are continually developing new compounds to increase durability, decrease weight, and improve shock absorbance. Whether you are doing R&D in the lab or transitioning to full production, McLube® Formulation Chemists and Technical Reps have the industry-related knowledge and experience necessary to design a custom-formulated release agent tailored to your new material or process.

Benefits

• Excellent release properties
• Tailorable gloss level (High, semi-gloss/ satin, and matte)
• Limited transfer and in-mold buildup over time
• Solvent-based options and dilutable, water-based options
• No interference with post-finishing steps
• Improved line efficiency
• VOC-free solvent-based options also available
• Electrostatic application-compatible products
• Excellent surface appearance, reduced porosity
• Tin catalyst-free formulations
• Consistent release characteristics that are easy to control
• Extend the lifespan of molds, tooling, and dummy lasts