The Technology And Basic Principle of Processing High-density Sponge
The polyurethane sponge of the sponge manufacturer is a low-density PU with a relative foam density of less than 18kg/m3. The general method is that the amount of water exceeds 4.5 parts, and the amount of TDI exceeds 55 parts. It is easy to release. During the whole process of polyurethane foaming, the temperature is automatically raised above 180 °C, which will cause the foam to catch fire and cause a fire accident risk.
Sponge is a kind of polyurethane material foam plastic, which belongs to soft plastic polyurethane material foam plastic. Because of the porous structure of honeycomb structure, it has the characteristics of high-quality flexibility, ductility, water absorption and wear resistance, and is widely used in fabric sofas, mattresses, clothing, plastic flexible packaging and other fields.
Sponges are mostly made of methacrylate propylene glycol and methacrylate glycerol, which have a low degree of polymerization (2-3), a low hydroxyl value and a large content. The most common is methylbenzene diisocyanate, commonly known as TDI, which has two isomers, namely 2,4-TDI, 2,6-TDI. In the production of sponges, 2,4-TDI accounts for 80%, 2,6 -TDI accounts for 20%
In the production of sponges, water cannot be lacking. Water reacts with TDI to release CO[sub]2[/sub] vapor, which also plays a role in chain growth. Sponge manufacturers promote nitrile rubber and isocyanate to react with metal catalysts for chain growth, such as stannous acid and dibutyltin. There are triethanolamine, triethylenediamine, triethylamine, etc. metal catalysts that promote the chemical crosslinking reaction and can promote the vapor released by the reaction between acrylate and water. Commonly used are low-melting fluorocarbon compounds, such as monofluorotrichloromethane (F-11). Because it is not environmentally friendly, cyclopentane is generally used to replace F-11, or dichloromethane, which is actually better. If it is not for the production of very light and relative density sponges, the proportion of key raw materials can also be adjusted appropriately, and no external application of styrofoam is required.
Foam thickener (foam stabilizer) is a common silicon material foam thickener. At this stage, the key use of silicon-carbon bond Si-C prepolymer is 0.5%-5%. In the whole process of sponge formation, there are mainly The whole process of chain growth reaction, polyurethane foaming and chemical cross-linking is related to the molecular formula, degree of polymerization and content of raw materials.
At this stage, most of the sponge manufacturers use the one-step van polyurethane foaming method, mixing various raw materials at a high speed, and adding them to the forming box quickly, in which chain growth, polyurethane foaming, chemical cross-linking, Drying and other reflections, and then proceed to sponge production. The advantages of this processing are short production process, low viscosity of raw materials, energy saving, small investment in machinery and equipment, and wide coverage of available relative density.
