(A) talk about the equipment
Slow rebound sponge foaming equipment and ordinary cotton foaming equipment is basically the same.
The country now uses two types of foaming: manual foaming and assembly line foaming. General small sponge factory with manual equipment hair, large scale, well-financed manufacturers with assembly line equipment hair.
Sponge just entered our country, production equipment is mostly imported from abroad, manual foam equipment is no exception. The impact is relatively large, such as the German Hennecke company manufacturing semi-automatic foaming machine. (In 2012, I saw a 1983 factory in Indonesia, the machine is still in normal use, the heart is quite shocked!)
The semi-automatic foaming machine works as follows: polyether and small materials are pumped into a suspended storage barrel through a metering pump, and TDI is pumped into another storage barrel suspended from the mixing barrel through a metering pump. After preparing the mold, the mixing barrel is lowered to the center of the mold, the polyether and small materials are unloaded into the mixing barrel, the mixing rod is lowered and the materials are stirred well at low speed, then the TDI is quickly unloaded and stirred at high speed for 3-5 seconds, the mixing rod and barrel are quickly lifted to let the materials spread evenly into the mold and start to emulsify, rise and gel, the mold can be removed after 5 minutes, then the sponge is moved to the maturation area for maturation. The advantage of this equipment is: weighing, loading and unloading all done by the machine, high accuracy, labor saving, even spreading of the material; disadvantage is: relatively speaking, the equipment investment is large; in addition, each after a bubble, to clean up a mixing barrel, the efficiency is not high.
With the progress of domestic sponge foaming technology, the domestic manual foaming machine manufacturing technology is also becoming increasingly mature. Now many sponge factories are using split foaming machine. This kind of foaming machine, stirring barrel directly connected to the motor, the motor is equipped with a large frequency converter, to ensure that the stirring speed within 0.5 seconds from 0 to 1000rpm or more.
The operation is as follows: all kinds of materials are weighed by hand, polyether and small materials are added to the mixing barrel in turn, after stirring at low speed, stirring is suspended for a minute or so, TDI is put in, stirring at high speed for 3-5 seconds, the mixing barrel is pulled down, so that the mixture flows into the mold, spreading, emulsifying, starting, gel, the mold is removed in 5 minutes or so, and the sponge is moved to the maturing area for maturing. The advantage of this equipment is that it is easy to operate, and by changing different types of mixing barrels, large density, small density, large single and small single can be done. The disadvantage is that the material and liquid spreading is not uniform, the process conditions are difficult to control, the resulting product quality uniformity, stability is not strong, and the loss is large.
Recently went to some places, found that the semi-automatic foaming machine and the trend of re-entry, which also shows that the development of the domestic sponge industry situation to the good. Flow line foaming machine has become more popular, many domestic manufacturers, the products are more or less the same, the main difference in the mixing head and control operation, some with LCD monitors, some with digital display, so to speak, each has its own characteristics. No longer detailed.
(B) talk about the process
With the formula, but also rely on good equipment and through the control of strict process conditions to complete the production.
A, mixing head type
Most of the flow line foam machine stirring head is wolf tooth bar type, the shear force generated is sufficient to meet the needs of mixing, no longer detailed. Manual foam machine stirring head, I recommend the suction cup type, that is, according to the type of mixing barrel, in a suitable round steel plate, symmetrical drilling 4-5 3-5cm round hole, this type of stirring head rotation, not easy to roll into the air, TDI added is not easy to be dropped out (propeller type stirring will occur in this case).
Second, stirring speed
Before adding TDI to the manual foam machine, the mixing speed should be controlled at about 300rpm, and after adding TDI, the speed should be increased to about 900rpm within 0.5 seconds. The speed is too low or too high, and the sheep aperture issued is rougher. Flow line foam machine mixing head stirring speed control at 4500-5000rpm can be. Some masters have to use 6, 7,000 rpm speed to foam, the effect is not necessarily good. Because the slow rebound formula in the slow rebound polyether molecular weight is relatively small, the viscosity of the material is not large, do not need too high shear force. Must use such a speed, can only be excessive mixing, the bubble hole structure is not beneficial.
Third, the material temperature
Manual bubble material temperature control in 25 ± 1 ℃, assembly line bubble material temperature control in 22 ± 1 ℃. In the south, the material temperature should be relatively low, because the ambient temperature is relatively high for a long time; in the north, the material temperature should be moderately high, because the ambient temperature is relatively low for a long time. Especially the manual foam, material temperature must be controlled, because the manual foam foaming process can not control too many factors. If the operator does not cooperate well, lengthen the operating cycle, the material liquid in the mixing barrel for a long time, due to stirring friction heat, material temperature and room temperature, the material temperature continues to rise; ambient temperature is lower than the material temperature, such as the heat generated by friction is not enough to compensate for the loss of heat caused by the low ambient temperature, the material temperature will naturally fall. When the ambient temperature is higher than the material temperature, the material temperature will rise significantly. Whether the material temperature rises or falls, if the deviation from the predetermined temperature is large, there are effects on the foaming. This is because the formulation is set at a predetermined temperature.
In general, the lower the material temperature, the better the foam pore size, the better the performance indicators of the sponge; the higher the material temperature, the more scattered the foam pore size, rough, the worse the performance indicators of the finished product. Some masters say, I’m in more than 30 degrees as usual foaming. I do not know, every 10 ℃ temperature rise, the speed of chemical reaction accelerated 2 times, we think about how the controllability of such operation.
I have monitored the line foam nozzle material temperature, the feed temperature is 22 ℃, the mixing head in the residence time of 1 second, mixing head speed 5000rpm, the liquid just out of the nozzle, the temperature has reached 32 ℃, and the room temperature was only about 25 ℃. This shows how great the impact of mixing on the material temperature.
Fourth, the preparation of additives
Manual bubble does not need to prepare additives, as long as the feeding coefficient is accurately weighed and added to the mixing barrel.
Flow line bubble need to be part of the additives with polyether dilution, in order to meet the working characteristics of the pump. The concentration of additives should be appropriate.
Amine with polyether with a concentration of 30% is fine, D22 with a concentration of 1%. Porous agent with a concentration of 50% can be.
Foaming process such as the need to adjust the amount of additives, if the concentration is too high, it will make the adjustment range becomes larger, the result is often overkill; too low will make adjustments to produce serious lag, the above practices are not conducive to production. Some masters of tin with 1/400 concentration, the need to adjust the amount of tin, keep adding and subtracting, just can not immediately achieve the desired adjustment effect.
V. Chain speed
Manual bubble does not exist chain speed problem. The flow line bubble chain speed should be controlled.
In general, the slow rebound assembly line bubble chain speed to be lower than the ordinary bubble. Too fast will pull down the bubble. Because the slow rebound sponge with less water, slow start, slow heat, less heat, bubble gel speed is much lower than ordinary sheep, therefore, the chain speed is generally controlled at about 3.8 m / min can be. Of course, experienced masters can adopt the chain speed they can control.
Six, gas injection
In order to ensure that the slow rebound sponge open hole, if necessary, to the mix head in the gas injection. Of course, the manual bubble does not have the problem of gas injection. The flow line bubble must be considered for air injection. The smaller the density, the smaller the amount of gas injection, the greater the density, the larger the amount of gas injection. Sometimes limited to the range of the gas flow meter installed on the equipment, want to increase the amount of gas injection but can not do, which should be in the design of the formula to determine the foaming process before taking into account this problem, such as by increasing the amount of opening agent, reduce the amount of tin, reduce the amount of silicone oil, increase the material temperature to achieve.
(C) talk about site judgment and control
Then the good formula, only through the production, manufacturing high-quality products, in order to reflect the value of the formula itself contains. Therefore, only to achieve the accurate judgment and comfortable control of the problems that arise in the production process, in order to achieve the objectives of the formula design.
In most cases, the production conditions and the small test conditions are quite different. Many formulations, small test no problem, a machine production, the problem came a whole lot.
Slow rebound sponge preparation process is most likely to appear in the problem of closed hole, cracking, collapse bubble, sinking, coarse holes, compression bars, internal local rotten core, etc., then you can not hold the formula, but to immediately make a judgment, find the cause and make adjustments.
A, there is no closed hole, manual bubble is easy to find, is to remove the mold, the four corners of the sponge with a hand pinch, if the closed hole, there is a pinch or bloated full of feeling, most of this situation is because the formula in the opening agent less or tin more than the reason. If the sponge surface dry faster, continue production, according to 3%-5% of the amount of tin decreases; if the surface dry slower, and then do it according to 3%-10% of the amount of increasing the opening agent. Flow line bubble only out of the baking channel can be checked, there is a closed hole, the treatment method as above.
B, cracking there are horizontal plane cracking and longitudinal line cracking. Most of the horizontal cracking is the amount of tin is not enough, then you can see the sponge open-hole sex is quite good, add about 5% tin can be solved; longitudinal cracking and mixing strength is not enough, mixing time is not enough, appropriate adjustments can be made. Sometimes the amount of TDI is not enough may also lead to cracking, pay attention to this problem.
There are two reasons for collapsing bubble: one is to forget to add silicone oil or the amount of silicone oil is seriously insufficient; the other is to forget to add tin or the amount of tin is seriously insufficient.
C, there is sinking is generally with the silicone oil is not good or the amount of just on a critical point: only to support the non-collapse, but not enough to maintain the initial stability of the system.
D, sponge cut, only after the problem can be found: coarse holes, compression bars, rotten core:.
1) a coarse hole is related to the quality and dosage of the opening agent, has been mentioned in previous articles. Second, the amount of TDI is not enough. Third, the material temperature is too high, and fourth, the mixing speed is too low or too high.
2) Slow rebound in the pressure tendons mostly related to the mixing is not in place, but also with the emulsion is too fast related.
3) sponge internal rotten core, and this core for a long time still sticky, because the mixing is not uniformly caused.
E, slow rebound sponge if there is closed-hole shrinkage, since out of the mold 30-40 minutes can be seen, this time to do post-processing. Generally available methods are manual stepping, board beating, peeling and deflating, high-pressure gas injection. The most simple and effective or manual trampling, not easy to hurt the sponge, you can seize the situation depends. When the day is cold, once can not, more than a few times, sun and step, step on the sun, as long as the quality of the opening agent is good, it can be completely restored.
