Small gauge production block foam on weekdays adopt box foam process, which is a gap production process.
This kind of foaming method is developed on the basis of manual foaming in the laboratory.
After the reaction material is mixed, it is immediately poured into a wooden or iron box made of the same open mold foaming molding, hence the name "box foaming". Box foam molds (boxes) can be rectangular or cylindrical.
In order to avoid the foam block forming the arch round top, a floating cover plate can be set at the upper part of the foam box. When foaming, the cover plate is attached to the top of the foam body and gradually moves upward with the rise of the foam body.
Box foam important equipment includes: (1) electronic mechanical stirrer, mixing barrel; ② Mold (box); ③ weighing objects, such as scales, platform scales, measuring cups, glass syringes and other measuring instruments; ④ A stopwatch for controlling the stirring time. During production, the inner wall of the box should be coated with a large number of release agents to make the foam easily out.
The advantages of adopting box foam production are: less investment in equipment, small footprint, simple layout of equipment, simple and convenient operation and repair, flexible production. Some small enterprises and township enterprises with insufficient funds in China use this method to produce polyurethane foam.
The pre-box foaming is the technique of non-continuous production of soft foam, so that the production efficiency is lower than the continuous selling method, and the equipment is mostly manually controlled, and the labor intensity is larger. Production capacity is limited, foam cutting loss is also larger.
Box foam process parameters should be controlled in a certain scale, because even if the same formula, adopt different process parameters produced by the foam function is not necessarily the same. The material temperature was controlled at (25士3) 7, the stirring rate was 900 ~ 1000r/min, and the stirring time was 5~12s. Before adding TDI, the stirring time of polyether and additives mixture can be flexibly controlled according to the environment. After adding TDI, the stirring time is 3~Ss. The crux of the problem is that after participating in TDI, the mixture will be close to the average.
In box foaming, the following aspects should be paid attention to:
(1) Preparation before production, including material temperature, mechanical equipment inspection;
② measurement should be accurate;
(3) suitable to control the mixing time;
(4) Dumping mixture liquid should be agile, light and steady, not too hard;
(4) the box is put safely, the bottom paper is placed flat, to avoid the uneven material flow when the material is poured;
When the foam rises, the gland should be light, ensuring the natural stability of the foam rebound;
The auxiliaries with floating is now used, the pre-mixture can not be long.
So far, there are two kinds of foaming equipment. Finally, the ingredients are weighed into a container according to the formula, mixed with a high-speed blender, and poured into a box mold to foam.
In this method, there are many residual materials in the mixed container. The material is transported to the mixed cylinder by metering pump and stirred evenly. Mechanical assembly takes the initiative to close the bottom of the cylinder, and the material is pressed into the foaming box by compressed air for foaming molding.
These two sides will be due to the material into the box speed through the fast eddy, may make the foam finished feather! The guest got stuck.
The most legitimate box-type foaming assembly is to place the hybrid cylinder without the bottom of the cylinder indirectly in the middle of the foaming box. The metering pump will transport all kinds of materials needed for foaming into the hybrid cylinder. After a few seconds of stirring and mixing, the promotion of assembly will lower the hybrid cylinder and separate the foaming box, and the foaming materials will float safely at the bottom of all the boxes. In this way, the foam will not produce F crack due to the eddy current of the material, and the foam height is relatively uniform. Can compress ten thousand assembly on the shrinkage foaming material, make the flat top foam, in order to reduce the cutting waste. This kind of assembly is only suitable for the production of polyether type polyurethane foam and high rebound foam.
Because of the high viscosity of the material, the method of continuous production is generally adopted.