At Concentrol we are experts in mold release agents, and one of our specialities is mold release agents for shoe soles. The knowledge and experience on the raw material used and on the needs of the product are key to offering the best solutions to manufacturers.
In the case of shoe soles, depending on what footwear’s sole component (polyether or polyester), one or other Concentrol demolding agent is applied. Manufacturers use polyester or polyether according to their needs and desired result. The formulation based on polyester is characterized by being more economical, with lower viscosity, more reactive, susceptible to biological attack, less durable and because it is solid at room temperature it requires a lower mold temperature. On the other hand, the polyether base needs a higher mold temperature and curing time, it has a higher cost, higher viscosity, better abrasion and chemical resistance properties, resistant to temperature and suitable for markets that value durability.
Needs according to types of soles
Depending on the type of sole that is used, a different release agent is required. Apart from the material used (polyester or polyether), we must bear in mind that currently on the market we find two types of soles (one density or two densities), which require different injections.
In the case of single density soles, after applying the release agent, polyurethane is introduced by casting into the mold. Then the sole is demolded. Soles are often subjected to subsequent treatments to improve their adhesion or appearance, for example by degreasing or painting. Afterwards, the soles are adhered to the rest of the shoe by means of adhesives or sewn. In the case of high-density soles, ease of demolding, low mold fouling and compatibility with subsequent treatments are highly valued.
The difference between processing single-density and two-density soles is that the latter have to achieve the adhesion of the sole to the midsole during the molding process itself. Also, in the case of two-density soles, the sole is cast and closed with a false lid. The lid is lifted, the midsole is cast on the back of the sole, the lid is closed and the sole is left to cure. The sole obtained after unmolding is adhered to the rest of the shoe. It is very important for the process that the release agent does not interfere at all in the adhesion of the sole and the midsole.
In any case, the objectives of the mold release agent are the same: to achieve a high demolding power, impeccable finish in terms of shine and uniformity of the surface, low mold fouling and adaptation to the complexity of the parts depending on fashion.
In order to ease the process by eliminating adhesive and sewing, thanks to the high quality of our shoe release agents we can make a direct injection of mono and bi-density soles. The process consists of molding and bonding the sole onto the footwear at the same time. The upper part of the footwear acts, both in mono and bi-density, as the last lid after casting the polyurethane. The choice of a good release agent is very important here, as the result has to be a perfect sole, uniform shine, excellent demolding, low fouling and, where appropriate, good adhesion between the sole and the midsole.
Main objectives
At Concentrol we work with the commitment to always achieve the highest quality in our products. Mold release agents for shoe soles are one of our specialities and we have achieved some of the main features required by the product according to each manufacturer’s needs. Following we outline some of the advantages of Concentrol’s release agents for footwear soles: firstly, we highlight the high release capacity, the perfect adhesion on bi-density soles, a level of shine and optimal surface finish and compatibility with subsequent treatments. Also we highlight the differentiation of products according to whether they are polyether or polyester soles, as it is explained at the beginning of this document.
Another of the goals achieved by our footwear release agents is that they are solvent-based and water-based products with low levels of rejection. In addition, they cause low mold fouling. Regarding the environment, we highlight the low emissions of VOC and the possibility of DBT or tin free products.
The range of release agents for shoe sole demolding has lines based on water and solvent base, as well as auxiliary products for demolding such as a mold cleaner or reinforcing paste.
