Application of low oil absorption activated calcium in polyurethane foaming material
Polyurethane foam is a two-component material, composed of A-component polyol and B-component isocyanate, under the action of foaming agent, catalyst, flame retardant and other additives, it is mixed by special equipment, and foamed by high-pressure spraying to become a polymer.
Figure 1.Polyurethane foam applications
Polyurethane foam can be divided into two types: soft foam and hard foam. Soft foam is open-cell structure, the main function is cushioning, commonly used in sofa furniture, pillows, cushions, insoles, toys, clothing and soundproof lining. Rigid foam is closed-cell structure, polyurethane rigid foam is a new type of synthetic material with thermal insulation and waterproof function, and its thermal conductivity is low, only 0.022-0.033W/(m-K), equivalent to half of the extruded plastic board, and it is the lowest thermal conductivity of all the thermal insulation materials. Rigid polyurethane foam is mainly used in building exterior wall insulation, roof waterproofing and heat insulation integration, cold storage heat insulation, pipeline insulation materials, building panels, refrigerated trucks and cold storage thermal insulation materials.
Heavy calcium carbonate is one of the most commonly used fillers for polyurethane foaming materials, filling in the A component of polyurethane foaming materials, mixing the A component and the B component and spraying foaming, i.e., making the required polyurethane foaming materials. Calcium carbonate is mainly used in polyurethane foam to adjust the density, mechanical properties and reduce the cost of the material. However, heavy calcium carbonate is easy to precipitate in component A (polyol), which is unfavorable for storage and transportation.
Figure 2. 2000 mesh heavy calcium in Figure 3.Low oil absorption activated calcium in the
Polyurethane A component storage 48h state Polyurethane A component storage 48h state
Solution Measures
1. Adopt ultra-fine heavy calcium, the finer the filler, the slower the settling speed, but the method treats the symptoms but not the root cause, and can only prolong the settling time;
2. Reduce the amount of filler added;
3. Use mixed filler, mix heavy calcium with other filler (such as heavy calcium and light calcium), can reduce the precipitation phenomenon;
4. Increase the viscosity of component A (polyol), by increasing the viscosity of polyol, it can slow down the settling speed of heavy calcium;
5. Before spraying, carry out high-speed stirring or vacuum stirring for component A (polyol) to remix the precipitated heavy calcium, but this method affects the construction efficiency, and if there is hard precipitation, it is impossible to stir away.
All the above methods have their own disadvantages. To address the above problems, our company has developed a low oil absorption series of activated calcium, which not only solves the problem of precipitation (as shown in Figure 3), but also improves the filling ratio, and has less impact on the mechanical properties of polyurethane foam, such as strength, modulus, and so on.
