How to choose the small material in a slow rebound sponge recipe

How to choose the small material in a slow rebound sponge recipe
Slow-rebound sponge formulations are similar to those for ordinary cotton. Apart from the major differences in the main material, polyether, certain small materials can be used interchangeably. However, in order to produce high quality products, the choice of small materials should still be carefully selected.

I. Selection of amines

The most classic amine for slow rebound sponges is Dabco 33-LV from American Air, the dosage of which is generally 0.3-0.8 parts of the total polyether. It is a combination of 33% triethylenediamine and 67% mono-dipropylene glycol (DPG). This product is recommended because it uses a solvent of mono-dipropylene glycol. One may ask, is one solvent so important? The answer is yes. In terms of its ability to dissolve triethylenediamine, there are many other alcohols that can be used as solvents: propylene glycol, diethylene glycol, ethylene glycol, 1.4-butanediol, etc. But of these small molecule alcohols, only mono-dipropylene glycol has the highest molecular weight and the lowest hydroxyl value. As we all know, small molecular weight alcohols can be used as chain extenders or cross-linking agents, which means that these small molecular alcohols can consume TDI, with the result that on the one hand, the TDI index is reduced and on the other hand, the sponge is prone to closed pores.

Before 2012, only a few countries were able to produce DPG with a purity of 99% or more, and only one plant in Anhui could produce DPG with a purity close to 95%, which is a few percentage points less than the purity of DPG and could not be used as a solvent because it condensed at room temperature. As a result, the most available amines on the domestic market are those formulated with ethylene glycol as the solvent. Some catalyst manufacturers, in pursuit of profit, deliberately reduce the concentration of triethylenediamine, with such amine foaming, to ensure the catalytic capacity, it is inevitable to increase the amount of catalyst, this catalyst containing a large number of small molecules of solvent, will consume too much TDI, if the amount of TDI is not adjusted, the sponge will become soft, the tendency to increase the closed pore. In addition, the slow rebound tension and tear strength issued by this amine are not good.

It is believed that with the progress of domestic chemical separation engineering technology, more and more high purity DPG will be introduced, and more and more domestic Dabco 33-LV will be produced. Of course, some other amines can also be issued slow rebound, such as 9727, CS90, etc., but before using must do a rigorous small test, production to consider the amplification effect. It is not recommended to use SMP for slow rebound. In winter when foaming is difficult, you can add 0.1-0.3 parts of A1 catalyst to strengthen the foaming reaction.

II. Selection of tin

The master who has sent ordinary cotton likes to use tin octanoate (T-9) to send slow rebound, but I suggest using dibutyltin laurate (D22, T-12, also known as K-19). Stannous octanoate is suitable for medium and low density sponges. It is characterised by a fast tackiness at the beginning, but not enough strength at the end. T-9 is easy to hydrolyse, slow rebound itself is slow to start (generally control the starting time in about 160 seconds), its contact time with water is long, there will be part of the hydrolysis off, affecting the maturation. Dibutyltin dilaurate does not hydrolyse, starts, gels, cooks smoothly and has good post-ripening properties.

Some colleagues once said that the sponge pulling force is not good, I suggested using dibutyltin laurate, the feedback is that the pulling force has improved. If you use T-9, the dosage is 0.1-0.4 parts. If you use dibutyltin dilaurate, the dosage can be controlled between 0.03-0.05. In the case of in-line slow rebound, the dosage can be reduced to 0.001-0.01 parts. For export orders that restrict the use of tin catalysts, the author suggests using bismuth naphthenate to replace tin on it.

The choice of silicone oil

Typical slow rebound silicone oil is B8002, the amount of which is between 0.5 and 2 parts. High density sponge is used sparingly, low density sponge is used more. Hand foam more, machine hair less. In recent years, domestic silicone oil suppliers have developed a number of silicone oil for slow rebound, performance is also good. Also useful L-580 hair slow rebound, when the amount of silicone oil to reduce, after all, L-580 activity is relatively high.

Fourth, the choice of open-hole agent

Five, slow rebound sponge also used in flame retardant.

Six, the use of pigments and ordinary cotton basically the same, also skipped. Just encounter black sheep to pay attention to, because the preparation of black colour paste carbon black has hydrophobic, will affect the compatibility of the various components of the formula and the efficiency of the catalyst, many colleagues have encountered black sheep easy to crack the phenomenon, the reason here. Therefore, the amount of catalyst should be adjusted appropriately when making black slurry. This is a personal working experience, for reference only, and I welcome criticism from colleagues.