Shoe Sole Manufacturing

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Release Agents and other ancillaries for Shoe Sole Manufacturing

McLube® offers a consummate line of release agents and ancillary products for shoe sole manufacturing processes, including single and dual-density casting and direct attach operations. McLube’s water and solvent-based formulas for shoe sole manufacturing can be catered to any process to ensure the release characteristics of the coating meet every customer goal and product specification. We have helped shoe sole manufacturers around the world reduce scrap and costs, lessen environmental impact, and improve overall process efficiency.

Products for Shoe Soling

Release Agents for Shoe Sole Manufacturing

We offer water and solvent-based options with tailored slip coefficients to achieve your process goals. Rely on our experienced Technical Representatives and Formulation Chemists to guide you through selecting, testing, and implementing the ideal release agent for your shoe soling process.

Mold Cleaners

Our mold cleaners for shoe sole manufacturers are formulated to reduce the amount of time and physical abrasion required to remove waxes, release agents, and thermoset residues from shoe soling molds. We offer water and solvent-based mold cleaners that can be safer, more effective alternatives to common cleaning solvents. Go to our industrial cleaners page to learn more, or contact McLube today.

Supported Shoe Soling Processes

Rubber Outsoles

Our rubber release agents are currently used to produce durable, wear-resistant rubber outsoles for military-style footwear, safety shoes, and more. Available release coatings for rubber outsoles include solvent-based and water-based release agents with semi-permanent characteristics to increase the number of soles produced per application and reduce in-mold buildup and stoppages for cleaning.

Single Density

Single or “monodensity” soles are generally produced with open pour casting (“open molding”) 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. Our polyurethane release agents for single-density sole casting are designed for compatibility with post-molding steps and minimal buildup.

Dual Density

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. Our 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.

Direct Attach Process

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 if the sole does not release properly, the upper shoe is also wasted. 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 tailor the slip coefficients of the release agent to create the optimal surface energy inside your mold to aid material flow without causing knit lines.

Supported Shoe Soling Materials

Shoe sole manufacturers are continually developing new compounds to increase durability, decrease weight, and improve shock absorbance. We support the following materials and may also custom formulate a release agent tailored to your unique sole materials:

Rubber soles, Thermoplastic rubber (TRP)
Polyurethane (polyester and polyether PU systems)
Ethyl vinyl acetate (EVA),
PVC, BPU, and acrylonitrile butadiene styrene (ABS).

FAQs

What are mold release agents?

A release agent (also called a mold release agent, release coating, or mold release coating) is a chemical coating used to prevent materials from adhering / sticking to other surfaces, typically the inside of molds or other manufacturing equipment and tools. Release agents aid in processes involving mold of parts, die-casting, tire manufacturing, and hose manufacturing, to name just a few.

Release agents are a little-know, often overlooked, process aid which make many of the things we use day to day possible to manufacture.

Release agents are typically liquid coatings but can also come in the form of pastes or powders. Most release agents are either water-based or solvent-based coatings and may be semi-permanent or sacrificial.

Click here to learn more about release agents and what type of release agent may be right for your manufacturing process.

How do I apply mold release agents?

How the release coating is applied directly impacts the performance characteristics of the coating. Molders must pay careful attention to application methods and ensure consistency day-to-day, shift-to-shift.

Improper application can cause reduced productivity, higher scrap rates, or even failure of the part to release from the mold.

Overapplication is the most common operator error. For semi-permanent release coatings, not allowing the coating to cure, if applicable, is also a common issue which leads many molders to assume the coating does not work for their material or application.

Release agents can be applied by many methods which are often process- or user-specific. Generally, release agents may be wiped, sprayed, brushed, or flow coated onto molds and tooling. Semi-permanent coatings may require time to cure on the surface before molding can begin. Sacrificial release coatings generally allow molders to begin molding parts as soon as the coating has been applied to the mold.

Heat often plays a factor in application methods (and the choice of release agent). For processes that involve heat or heated molds, such as rubber molding, manufacturers have many options. For some processes, manufacturers must wait for water-based release agents to dry before molding their first part. This can slow productivity in processes with little or no heat and sometimes a fast-drying, solvent-based release coating is better suited.

Spray application is generally preferred with fine atomizing spray guns or systems. Spray application aids in even uniform coverage of areas where materials stick to tooling. Spray application can be either air-assisted (forced air atomizes the liquid into fine droplets) or airless.

Mold release aerosols are also common in the industry, providing convenient, portable spray capability, although aerosol release agents may be impractical for some applications.

McLube product specialists not only help with product selection but also help customers optimize their application method. Contact us for application instructions tailored to your process.

Dilution tips and best practices

Diluting concentrated release agents offers molders more control over their process, reduces shipping costs, and can also allow molders to tailor coatings to different processes within their facility. In every case, consistency is crucial.

McLube recommends:

Placing one team, shift, or supervisor in charge of all dilution to ensure consistency.
Keep lids closed when not in use to prevent evaporation and contamination.
If the product requires agitation before use, mix periodically before AND during dilution.
Adding water to product, not product to water.
Regularly cleaning dilution equipment.
Testing dilutions in a lab setting before moving to the production floor.
Always consult your McLube product specialist before attempting dilution or if your molded material composition changes.

Follow this link to read more about dilution or contact us for assistance.

How do I properly clean my mold?

Follow all safety precautions when cleaning a mold and ensure proper personal protective (PPE) equipment is worn at all times.

Start by removing any buildup on the mold surface. Use the least abrasive methods possible to avoid damaging the mold surface. Selecting the right cleaning agent or solvent can reduce the amount of physical abrasion (and effort) required to clean your mold. Click here to learn more about our mold cleaners and industrial cleaners. If available, use compressed air to remove residues loosened by the cleaner or left over from mechanical scrubbing. Some molders may find it necessary to bead blast molds to remove tenacious residues.

Wipe the mold clean with a lint-free towel after all residues have been removed. It may be beneficial to rinse molds with clean water/ or a mold solvent to ensure all debris is removed. Ensure the mold is dry before application of release agent. If your mold will not be used or stored after cleaning, it is often beneficial to apply your release agent to the mold to protect it during downtime. Consult the release agent TDS or contact McLube® for more information about mold protective coatings.

Other Tips:

After applying a mold cleaner or suitable cleaning solvent, it is often beneficial to let the cleaning agent sit on the mold surface for a period of time to break down residues before scrubbing.
Mold cleaning can be a time consuming and expensive process. If your molding line experiences excessive downtime for cleaning, it may be beneficial to consider a different release agent or application method. Overapplication or improper cure of semi-permanent release coatings are common issues which leads to extra downtime for cleaning. In many cases, molders using sacrificial release agents can cut down on downtime due to cleaning by switching to a semi-permanent mold release agent.
During mold cleaning downtime, also clean dilution equipment (if applicable) as well as your application equipment.

Are there special considerations for RIM shoe 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.