The pu pigment manufacturer is to reveal the soft foam sponge box foaming process: small-scale foam production usually uses the box foaming process, which is an intermittent production process. This foaming method is developed on the basis of manual foaming in the laboratory.
After the reaction material is mixed, it is immediately poured into an open mold like a wooden or iron box for foaming molding, hence the name "box foaming". The box foaming mold (box body) can be rectangular or cylindrical. In order to prevent the foam block from forming an arched roof, a floating cover plate can be arranged on the upper part of the foaming box. The cover plate is tightly attached to the top of the foam body during foaming and gradually moves upward as the foam body rises.
The main equipment of box foaming includes:
①Electric control mechanical agitator, mixing barrel;
②Mould (box);
③Weighing tools, such as scales, platform scales, measuring cups, glass syringes and other measuring instruments;
④Stopwatch to control the mixing time. During production, a small amount of release agent needs to be applied to the inner wall of the box to make the foam easy to come out.
The main advantages of using box foaming method to produce soft foam are: less equipment investment, small floor space, simple equipment structure, simple and convenient operation and maintenance, and flexible production. Some small domestic enterprises and township enterprises with insufficient funds use this method to produce polyurethane soft foam. The pre-box foaming is a technology of discontinuous production of soft foams, so the production efficiency is lower than that of the continuous selling method, and the equipment is mostly manual operation, which is more labor-intensive. The production capacity is limited, and the cutting loss of foam plastic is also large.
The process parameters of box foaming should be controlled within a certain range, because even the same formula, the foam performance obtained by using different process parameters may not be the same. The temperature of the raw material is controlled at (25±3), the stirring speed is 900 ~ 1000r/min, and the stirring time is 5 ~ 12s. The mixing time of the polyether and additives mixture before adding TDI can be flexibly controlled according to the situation. After adding TDI, the mixing time is 3~Ss. The key is that the mixing must be uniform after adding TDI.

When box foaming, the following aspects should be paid attention to:
① Make preparations before production, including the temperature of raw materials and the overhaul of machinery and equipment;
②The measurement should be as accurate as possible;
③ Properly control the mixing time;
④ Pour the mixture liquid quickly, lightly and stably, and not use excessive force;
⑤The box body is placed steadily, and the bottom paper is flat to avoid uneven material flow when dumping;
⑥When the foam rises, the gland should be light to ensure that the foam rises naturally and steadily;
⑦All additives are prepared for immediate use, and the premix can not be stored for a long time.
So far, three types of foaming equipment have appeared in box foaming. At first, people weighed various raw materials into a container according to the formula, mixed them with a high-speed mixer, and poured them into a box mold for foaming. In this way, there are many residual materials in the mixing container. There is an improvement in the use of a metering pump to transport the raw materials into the mixing cylinder and mix them evenly. The mechanical device automatically closes the bottom of the cylinder, and the compressed air presses the material into the foaming box for foam molding. These two methods will cause eddy currents due to the material flowing into the box too fast, which may cause the foam products to plume and sink. The most reasonable box-type foaming device is to place the bottomless mixing cylinder directly in the center of the foaming box. The metering pump transports the various raw materials required for foaming to the mixing cylinder. After starting the mixing and mixing for a few seconds, the lifting device Then the mixing cylinder is raised to leave the foaming box, and the foaming material flows steadily across the bottom of the box. In this way, the foam will not be cracked due to the vortex of the material, and the height of the foam will be more uniform throughout.
A device can be pressurized on the expanded foam material to form a flat-top foam to reduce the waste of corners when cutting. This device is only suitable for the production of polyether polyurethane soft foam and high resilience soft slab foam. Polyvinyl urethane block mining Sayemo cannot use this method because of the high viscosity of the material, and it is generally produced by continuous method.