It is usually a box type foaming process, which is a gap type production process. The foaming method was developed on the basis of manual foaming in the laboratory.
After mixing the reaction material, it is poured into a wooden or iron case, which is made into the same open mold as foam molding, hence the name "box type foaming". The box type foaming mold (box) can be rectangular or cylindrical. In order to prevent the foam block from forming the arch round top, the floating cover plate can be set up on the top of the foam box. The cover plate is tightly attached to the top of the foam body when the foam is foamed, and gradually moves up with the foam body rising.
The main equipment of box type foaming includes:
(1) electric mechanical agitator, mixing bucket;
(2) die (box);
Weighing instruments, such as scales, platform scales, measuring cups, glass syringes and other measuring instruments.
(4) a stopwatch that is used to control the stirring time. In production, a small amount of release agent should be applied to the inner wall of the box, so that the foam will easily come out.
The advantages of box foaming method are: low investment in equipment, small area of land, simple structure of equipment, simple and convenient operation and maintenance, and flexible production. A small number of small enterprises and township enterprises in China are using this method to produce polyamine soft foam. The technology of producing foam by discontinuous foam is better than that of continuous selling method, and the equipment is mostly manual operation. Production capacity is limited, and the loss of foam plastics is also greater.
The process parameters of box type foaming should be controlled in a certain range, because even the same formula, the foam properties made by different process parameters are not necessarily the same. The temperature of raw materials is controlled at (25 1000r/min 3) seven, stirring speed is 900 ~ 1000r/min, stirring time is 5~12s. Before adding TDI, the mixing time of polyether and auxiliary mixture can be mastered flexibly according to the situation. After adding TDI, the stirring time is 3~Ss, the key is to be mixed and uniform after joining and TDI.
When the box foamed, we should pay attention to the following aspects:
(1) the preparation before the production, including the temperature of the raw materials, the maintenance of the machine equipment, and the accuracy of the measurement;
(3) the proper control of the stirring time;
(4) the dump mixture should be quick, light and stable, and can not be overforced; 6. The material flow is uneven; 1. When the foam rises, the gland should be light to ensure that the foam rises smoothly.
Up to now, there are three kinds of foaming equipment for box foams. At first, the ingredients were weighed into a container according to the formula, stirring and mixing with a high-speed mixer, and then poured into a box mold for foaming. In this way, there are more residual materials in the mixed container. After the improvement of the use of this metering pump, the raw material is transported to the mixing bucket and stirred evenly. The mechanical device automatically opens the bottom of the barrel, and the material is pressed into the foam box by compressed air. These two kinds of materials will generate eddy currents due to the excessive speed of material flowing into the box, which may cause foam products to come out.
The most reasonable box foamed device is to put the bucket at the bottom of the bucket directly in the center of the foam box. The metering pump sends all the raw materials needed for the foaming to the mixing bucket. After a few seconds of mixing and mixing, the lifting device will raise the mixing bucket and leave the foam box, and the foaming material flows smoothly to the bottom of the box. Such foam will not produce f cracks due to eddy current of materials, and the height of foam will be more uniform. It can pressurize ten thousand units on expanded foamed material and make flat top foam to reduce the corner waste in cutting.
This device is only suitable for the production of polyether polyurethane soft foam and high resilience soft block. This method can not be used because of the high viscosity of the material.
