In the past ten years, polyurethanes are rapidly used in various fields of industrial production, such as refrigerators, refrigeration, construction and other industries. Polyurethane rigid foam panel (referred to as PU rigid foam) has the characteristics of high bulk density, low water absorption, good dimensional stability at low temperature or high temperature, long service life and excellent thermal insulation performance. In particular, polyurethane foam panel with widely use, easy to use and good in heat preservation effect.
For the building applications, polyurethane panels can be classified into ordinary polyurethane panels and polyurethane sandwich panels according to the condition of the products; they can be divided into continuous panel production lines and discontinuous production lines according to the foam molding process. Intermittent panel material requires the foaming material to be filled with a thin and large volume cavity in a relatively short period of time, requiring excellent fluidity of the foaming system, good density distribution of the panel and excellent dimensional stability; continuous panel The foaming parameters are required to have suitable compatibility with the production line speed, and have excellent mold release properties in the later stage. In response to the above specific requirements, we have developed a foaming material system suitable for various production lines using special polyether materials and a suitable catalytic system, which are used in some well-known domestic production lines.
2.1 Stability Light weight, high strength, good dimensional stability
2.2 Strong adhesion Polyurethane rigid foam for steel, aluminum, stainless steel and other metals, wood, concrete, asbestos, asphalt, paper and polyethylene, polypropylene, etc. Most plastic materials have good bond strength. The strength of the bond between the foam and the face material directly affects the practical effect of the sandwich panel.
2.3 Excellent thermal insulation properties Polyurethane rigid foam has high closed cell ratio and extremely low thermal conductivity, so polyurethane rigid foam has the best thermal insulation performance in current building materials. The data shows that the use of polyurethane sandwich panels can save 60% of the heating costs of the exterior wall without insulation.
The process of continuous forming of horizontal sandwich panel: the foaming machine uniformly mixes the raw materials, and then sends it to the uniform moving surface material for foaming. At the same time, the upper layer material is combined with the foam to form a sandwich panel with the surface materials on both sides. Most of the materials used as the face material are aluminum foil and metal materials. During the foaming transfer process, the foam is matured in a double-layer pressure panel and cut to a desired length to produce a panel of the desired specification. The thickness of the sandwich panel can be adjusted by varying the distance between the upper and lower panel metal conveyor belts and the thickness of the side seal blocks. The thickness can be adjusted from 20 to 250 mm, the conveyor speed can be adjusted steplessly between 1.0 and 25 m/min, and the width of the panel can be adjusted between 600 and 1200 mm as needed. In the continuous sandwich molding production of panel metal, the distribution of reaction materials must be uniform. The mixing head simply pours the material back and forth. When the panel width is about 1 m, the production speed is generally limited to 9 to 10 m/min. Above this speed, when the mixing head moves and reverses, the reaction material tends to be excessive at the edge of the panel. In addition, the round-trip speed is too high and it is not safe to operate. The high-speed continuous compounding process is very sensitive to the temperature and the rate of reaction of a foam, especially a polyisocyanurate foam system. To reduce sensitivity, polymeric MDI with high viscosity specifications should be used. At present, China has more than 50 continuous panel metal production lines. Most continuous panel production lines are not operating at full capacity due to current market demand and other factors. As market demand increases and technology updates, continuous panel metal becomes the mainstream production method in the near future.