The mixed head of the mixing chamber is cylindrical. The basic form of the mixer is the stick type, and two rows of short sticks are arranged on the mixing shaft, and the material is evenly mixed by the high speed rolling of the mixer. The retention time (i.e. mixing time) of materials in the mixing chamber is usually 0.4 to 1.3s, which varies with foaming machine and material. Generally speaking, the flow velocity of the material into the mixing chamber is low. The mixing room is selected with high speed, high shear, and the volume of the mixing chamber is larger. The residence time of the material in the mixing room is longer to get more mixing energy. In the high pressure foaming machine, the large number of materials pass through the nozzle under high pressure to enter the mixing room at high speed. Because of its high kinetic energy, the low shear mixer is used more frequently, the volume of mixing chamber is smaller, and the stopping time of materials in the mixing chamber is shorter.
Mixing head nozzles can be generally divided into straight tube, speaker tube, dispersing disc and dispersing tube. In order to obstruct the rotation of the material in the nozzle and to reduce the splashing of the high speed ejected material flow on the conveyor belt, many kinds of rectification equipment can be installed inside the nozzle. The straight pipe is the weakest form of nozzle. It is used in a small flow reciprocating mixed head system. Through the reciprocating movement of the mixed head, the material is evenly distributed on the conveyor belt paper mold. The horn nozzle is an improved type of straight tube. The metal net or nylon net with a choking effect at the bottom of the horn is added to the end of the nozzle. The spray speed of the material is further reduced, the area is expanded, and the spatter on the conveyor belt is avoided.
The foaming machine with the balance plate method, through the use of the horn nozzle, can make the material evenly spread on the conveyor belt, and then cancel the reciprocating movement of the mixed head. As for polyester foam, because the initial viscosity of the material system is high, it is difficult to make the material liquid evenly distributed even if the horn nozzle nozzle is used. It is usually necessary to use the mixed head reciprocating system. An improved nozzle, planned for a fixed mixed head, is the intention of adding a plane spread disk below the outlet to uniformly distribute the liquid through the disk and then to the fixed mixed head. The fixing of the mixing head not only reduces the power consumption, but also reduces the disadvantages of the mixing head reciprocating and the threat of bubbles due to the impact of material flow. Another method of fixing the mixed head is to connect a horizontal material dispersing pipe at the lower end of the outlet of the mixed head nozzle, and distribute the material evenly on the conveyor belt paper mold. The material dispersing pipe can choose the single pipe or double pipe shunt, the quantity, aperture and spacing of the material and the width of the hole and the width of the foaming machine. The factors such as degree are reasonably determined to ensure the balance of material and liquid distribution.
The PE foaming machine is a typical high pressure mixer head with a smaller mixing chamber and mixer. The size of the foam aperture is influenced by the formula. In the low pressure foaming machine, the mixing speed of the mixing head and the air volume of the mixing head are mainly controlled. In the high pressure foaming machine, besides adjusting the mixing speed, the adjustment of mixing chamber pressure is also the main method to control the bubble size. The adjustment of the mixing head pressure is mainly accomplished by changing the size of the annular gap of the mixing chamber material outlet.
