Large bubbles sometimes appear in the foaming process of polyurethane foaming machine, which is a common foaming technical defect. How to solve the problem of large bubbles in polyurethane foaming machine must be considered in the construction process. Here, we put forward the following suggestions and do the following work to help solve such problems encountered in the production of polyurethane foaming machine:

1. Control raw material ratio and injection volume.
Control the proportion of polyurethane materials. Through a large number of experimental studies, experts found that when the total amount of injection remains unchanged, the proportion of black material is too large, the proportion of white material will appear soft bubbles, the proportion of cyclopentane will increase, and vacuoles will appear when the proportion of cyclopentane is too small. Uneven proportions of black and white materials will cause uneven mixing and foam shrinkage.
The injection volume shall be determined according to the technical requirements. When the injection volume is less than the technological requirements, the foam forming density is low, the strength is low, and even filling will not appear compact cavitation phenomenon. When the injection volume is greater than the process requirements, bubbles and leakage will lead to product deformation.

Polyurethane foaming machine

2. The temperature control of polyurethane foaming machine is the key to solve the problem of large bubbles.
When the temperature of polyurethane foaming machine is too high, the reaction is difficult to control. It is easy to see that the performance of the foam injected into the mold is uneven. At the beginning of the injection, the viscosity of the chemical reaction increases rapidly, and the foam has not yet been reacted. The results show that the injected foam can not push the first injection of foam into the bottom of the mold foaming process, resulting in the phenomenon of larger bubbles.
Polyurethane materials shall be subject to constant temperature treatment before foaming After repeated tests, we found that the foaming effect is the best when the temperature is controlled at 18 ℃ - 25 ℃, the preheating furnace temperature of foaming equipment is controlled at 30 ℃ - 50 ℃, and the foaming mold temperature is controlled at 35 ~ 45 ℃ The temperature of foaming film is too low, the fluidity of vacuole system is poor, the curing time is long, and the reaction is incomplete, resulting in vacuum. When the temperature of the foam film is too high, the gallbladder in the plastic is heated and deformed, resulting in serious reaction of the bubble system. Therefore, the temperature of foaming film and the ambient temperature of foaming furnace must be strictly controlled. Especially in winter, when the line is opened every morning, the foaming film, preheating furnace, foaming furnace, box and door body must be preheated for more than 30 minutes After a period of foaming in summer, the foaming system of polyurethane foaming machine must be cooled and cooled.

Polyurethane foaming machine has a great relationship with temperature, because foaming depends on heat. If there is no heat, the foaming agent in the system can not evaporate, and no foam will form. Heat comes from two aspects: one is the heat generated by chemical reaction, and the other is the heat provided by the environment. The heat of chemical reaction is fixed and not affected by external factors The heat provided by a single environment changes with the change of ambient temperature When the ambient temperature is high, the environment can provide heat for the reaction system, improve the reaction speed and shorten the reaction time. This shows that the foam foam is full, and the foam surface is similar to the core density. When the ambient temperature is low, some of the reaction heat is discharged into the environment. On the one hand, the loss of heat leads to the prolongation of foam maturity and the increase of foam forming shrinkage. The results show that the foaming volume of the same foaming material at 15 ℃ is 25% smaller than that at 25 ℃ On the other hand, the foam surface will form a layer of hard skins which are not foamed or not foamed, which will increase the amount of foam perfusion and increase the cost of foam production.

3. Pressure control of polyurethane foaming machine

The low pressure of foaming machine will make the mixture of black and white materials and cyclopentane unevenly, showing that the density distribution of polyurethane foam is uneven, local large bubbles appear, bubbles crack and bubbles are soft. The foam appears white, yellow or black stripes, and the foam contracts. Therefore, the pouring pressure of the foaming machine should be controlled at 13 ~ 16 MPa as far as possible.