The chemical solutions company Concentrol is structured into four major divisions: Performance Materials, Food Processing Aids, Additives and Adhesives.

The professionals in the Performance Materials division work mainly with two materials, polyurethane foam, which gives rise to various products, and wood, which is one of the company’s future bets.

Polyurethane foam release agents are a chemical speciality designed for the final application of the product. This product has a very high added value for the customer, and the choice of one release agent or others can be linked to many factors such as environmental impact, cost of use or efficiency.


Types of release agents

  • Solvent base

Originally, solvent-based release agents were almost always used, which were not very sustainable solutions and, in some cases, compromised the health of workers, as they were exposed to solvents. This exposure was measured using TLV / DNEL values, related to the solvents formulated in the release agents.

  • Water base

Gradually, original equipment manufacturers (OEMs) have put pressure on the industry to eliminate VOCs and thus make the switch to water-based release agents. This change has come in parallel with the formulation of release agents that achieve parts with a drier finish, which, for example, allows heating sheets and auxiliary textiles to be glued to their surface without having to sacrifice the ability to unmould.

Along these lines, one of the most difficult challenges in recent years has been to reduce the greasy finish that water-based release agents can give to parts.

  • Co-solvents

Co-solvents and hybrids are halfway between solvent and water-based release agents.

Co-solvent release agents contain 75 to 85% water base and 5 to 15% solvent. It should also be noted that these have a shorter drying time and produce better emulsions of waxes and active ingredients than 100% water-based systems.

  • Hybrids

Hybrid release agents are based on the fact that the vehicle of the active ingredients is 50% water and 50% solvent. In terms of functionality and finish of the parts, they are like solvent-based release agents, but their formulation contains half of the VOCs.

There are also a couple of other options, halfway between solvent-based and water-based release agents, which are concentrated release agents and electrostatic release agents.

  • More concentrated release agents

Some people choose to apply less amount of release agent, but more concentrated. This allows users to reduce TLV, VOCs and ultimately improve the health of workers who have direct contact with these substances.

  • Electrostatic release agents

This is the most technically sophisticated approach. The release mold gun is connected to a negatively charged electrical pole, while the work mold is connected to a positive pole. By applying a high voltage current, an electrostatic field is generated between the electrode at the tip of the gun and the mold. When the applicator presses the trigger to initiate the flow of the release agent, the aerosol particles are negatively charged. Given that the opposing loads are attracted, the mold attracts the release agent, efficiently covering its entire surface. This helps prevent unnecessary losses and reduces consumption and environmental impact.

Today, electrostatic solutions do not have strong odors or additional toxicity, and can be used with class I, II or III solvents.

The use of electrostatic release agents prevents excessive spraying of mold substrates, floors, and the surrounding environment. This, in practice, means that there is a large reduction in consumption, between 30 and 50% compared to conventional systems. In addition, with this system there is a significant reduction in VOCs emitted, also between 30 and 50%, which helps to improve the work environment.

Electrostatic demolding systems are usually applied through robotic systems, and this involves an investment in specific equipment. It is also important to note that spray guns will be larger and heavier than those commonly used. 


Tinless release agents, a relative success

Over time, the polyurethane industry has evolved its solutions to achieve components that are increasingly respectful of the planet.

Tin is an organometallic compound that has been neglected due to its strong impact on the environment. Although it was widely used for a long time, it is now hardly used because it is a component that is very difficult to degrade in the natural environment.

Release agent suppliers have been working to replace organotin compounds with other organometallic compounds. The truth is that the new solutions have been moderately successful, as the new materials have some limitations.

Important compounds based on tin are tin octoate, tin dibutyl dilaurate (DBTDL) and tin mercaptides. Certain lead, mercury and antimony salts have also been used. Replacing DBTDL as a catalyst with other non-organotin substances is made possible by cutting-edge knowledge, collaboration, and testing with customers to produce bespoke products.


Reducing flammability, a challenge under study

To reduce the risk of flammability of release agents, the best option is to switch from solvent-based release agents to water-based ones, although there are alternatives.

One option is to upgrade the release system to use a less volatile solvent.

The European Union polyurethane industry treats solvents according to European Directive 67/548 / EEC, which classifies them into three groups:

  • Class I: Highly flammable. Substances with a flash point below 21 °C.
  • Class II: Flammable. Substances with a flash point between 21 °C and 55 °C.
  • Class III: Fuels. Substances with a flash point above 55 °C.

For example, if a modeler used a Class I release agent, which may contain heptane and has a flash point less than or equal to 0 °C, the logical step is to change it to a Class II release agent with a flash point of 28 °C. This may contain C9-C10 naphtha.

Switching from a Class II system to a Class III system, based on isoparaffin and with a flash point above 55 °C, would again significantly reduce volatility. Switching to higher flash point solvents is a good way to quickly reduce VOCs and TLVs, but there is a price, and with the increase in flash point temperature, the drying time will be longer. Since it will take longer to dry the molds before pouring the polyurethane into them, keep in mind that work schedule at the production line will become more critical.


VOCs and their environmental impact

VOCs, Volatile Organic Compounds, are one of the most impactful pollutants in the atmosphere. These components are key to the formation of ozone in the troposphere and at ground level because they form nitrogen oxides that contribute to global warming.

The chemical reactions involved in the formation of tropospheric ozone consist of a series of cycles in which carbon monoxide and VOCs oxidize to water vapor and carbon dioxide, both of which contribute to climate change.

The European Union and the WHO, the World Health Organization, define a VOC as any organic compound with an initial boiling point less than or equal to 250 °C measured at a normal atmospheric pressure of 101.3 kPa.

Volatile organic compounds are organic chemical compounds that contain carbon atoms with a high vapor pressure at room temperature. This vapor pressure is related to the boiling point, and the lower it is, the faster the molecules evaporate in the air. 


TLV and DNEL, indicators to be taken into account for the health of workers

The TLV, the Threshold Limit Values, are the concentrations of substances suspended in the air. These are important values to keep in mind, especially for those who work with mold release agents.

TLVs mark the conditions under which it is believed that almost all workers can be repeatedly exposed day after day without showing adverse health effects.

The TWA, the Weighted Average Concentration, is the concentration of substances to which workers may be repeatedly exposed without adverse health effects, and is calculated for an 8-hour workday and a 40-hour week. These data are useful in defining the size and potency of the plant’s extraction capacity to ensure that the TLV for each solvent is not violated.

The DNEL, the Level Without Derivative Effect, is the level of exposure to a substance above which humans should not be exposed.

In accordance with EU law, manufacturers and importers of chemicals must calculate the DNELs of any chemical used in quantities of 10 tonnes per year or more, and incorporate it into their “Chemical Safety Assessments”.

DNELs measure the potential of the substance to cause adverse health effects. This potential will vary depending on the pattern of exposure to the substance, and is calculated to take into account:

  • The people likely to be exposed to the chemical, i.e., workers, consumers, or humans exposed through the environment.
  • The frequency and duration of the exposure.
  • The route of exposure, which may be dermal, inhalation, or oral.

To give a practical example, a C9-C10 desaromatized hydrocarbon, which is a standard aliphatic solvent commonly used as a carrier in release agents, contains the following: DNEL (skin contact) of 208 mg / kg body weight / day and DNEL (inhalation) of 871 mg / m³.

If a Class III C11-C12 hydrocarbon is used, the DNEL disappears.