In the production of polyurethane products, release agents are essential for helping the molded items detach from the molds. The active release components, which could be substances like wax, organosilicon, and organic fluorine, generally make up less than 10% of the release agent. Over 90% of the agent consists of solvents that aid in evenly distributing the release component over the mold’s surface. This article delves into the roles of solvents in polyurethane release agents.
During molding, the material contacts the mold surface, which may have minor defects, creating friction when the product is removed. Injection or extrusion processes can form negative pressure or physical/chemical bonding between the mold and the material, making removal difficult. To reduce adhesion, release agents that form isolation films are used. These agents create a barrier between the mold and the product, easing the release process.
Phase One:
Early industrial production prioritized high solubility and volatility in solvents without considering environmental or safety impacts. Solvents were used as diluents to quickly evaporate post-application, preventing foam surface issues. Common solvents included:
1.Dichloromethane: Strong solvency, stable, non-flammable, but toxic vapors and environmental impact made it less favorable.
2.Petroleum Ether: Highly volatile, but often contained benzene and ketone impurities, leading to poor VOC and odor performance.
3.Naphtha: Extremely volatile and flammable, with harmful vapors.
4.Xylene: Flammable with a strong odor, and classified as a carcinogen.
5.Cyclohexanone: Known for its strong odor and carcinogenic properties.
Phase Two:
With increasing health awareness, heptane became a popular alternative due to its lower toxicity and high volatility. However, industrial-grade heptane contained impurities affecting its performance and posed risks of chronic toxicity with prolonged use.
Phase Three:
Environmental regulations prompted the search for safer solvents. De-aromatized solvent oils, produced through high-pressure hydrogenation and distillation, emerged. These solvents offered low toxicity and higher safety but evaporated slowly, causing potential foam issues on polyurethane products.
Phase Four:
Stricter safety and environmental standards led to the development of water-based release agents. While effective in many applications, water’s slow evaporation and the complex mold structures in seat foam production made high-flash-point organic solvents preferable. These solvents, with flash points above 60°C, were classified as non-hazardous and could be stored and transported as regular chemicals.
Phase Five:
The focus shifted to reducing odor and VOCs. High-end automotive interiors required release agents with minimal odor and VOCs. Isoalkanes, with properties like high purity and low toxicity, became ideal despite their high cost. The production of isoalkanes from coal-to-liquid processes in China promises to reduce costs and increase usage.
In conclusion, the quality and price of release agents are closely linked. High-end products demand higher costs to cover research and development, while low-cost agents often fall short in meeting advanced requirements.
