I often receive calls from colleagues from all over the world to ask about the various technical problems in the production of slow rebound sponges. In fact, these problems are encountered by everyone in the actual production process, including myself. What are the reasons?

After all, polyurethane is also a chemical industry, and these problems actually involve the problem of every raw material.

Every raw material that participates in the chemical reaction is very important, whether the main material or the small material has its unique effect, so if one of the raw materials changes in the chemical reaction, then it will naturally be reflected from the foam body in the foaming process, which is the most basic principle and the problem if it is not morbid, then it is a revelation.

If it is morbid, then we have to consider what to do to solve it; if it is a revelation to us, then we have to consider how to use it or improve it, you know, many evolution and inventions are developed in revelation.

For example: we all know that there are 2000 of Shanghai Gaoqiao and 1070 of Jinpu in Nanjing. Although the hydroxyl values of these two kinds of slow rebound polyether are both 240. however, in the actual production, their chemical activities are quite different. A few years ago, 2000 and 1070 could be used for each other without adjustment on other raw materials.

However, a few years later, they have formed their own characteristics, and they can no longer replace each other intact.

Of course, the domestic production of slow-rebound polyether is far more than these two manufacturers, so it is difficult to unify the raw materials used by each slow-rebound sponge manufacturer, including a variety of small materials.

As a result, each enterprise has its own formula, and the slow rebound polyether has good porosity and stability.

The amount of slow rebound polyether with better opening porosity in the production process is a little less, while the amount of silicone oil (stabilizer) is a little bit higher than that of silicone oil (stabilizer). On the contrary, if you use slow rebound polyether is more stable or closed, then the use of pore opening agent in the production process will be a little more, while the amount of silicone oil will be slightly reduced.

So how to determine the amount of pore opener and silicone oil?

In the polyurethane industry, due to the differences between slow rebound sponges and other sponges, such as ordinary high rebound sponges, no matter how many manufacturers there are, their production formulations can be said to be more or less the same, or even basically the same. however, the slow rebound sponge is different from its ever-changing formula, so it is absolutely impossible to locate the dosage of opening agent and silicone oil by mode, but no matter how the basic principle is still not separated from it.

No matter how to change, as long as you master its rules, you can easily operate it. No matter what the density of the slow rebound sponge you send, as long as the sponge can release a little air at the end of the reaction, the bubbles must not be too big, and the bubbles will be thicker as the pores are bigger. This also shows that there are two problems: a silicone oil is not added enough, and it is necessary to increase a certain proportion of silicone oil.

Second, if the opening of the sponge shows that the stomata are normal, then the addition amount of the opening agent is on the high side, and the addition amount of the opening agent should be reduced.

Catalyst.

The catalyst has a great effect on polyurethane foam, and only with it can the rapid production at room temperature be realized.

There are two main types of catalysts: tertiary amine and metal catalysts, such as triethylenediamine, pentamethyldiethylenetriamine, methylimidazole, Amur1, etc. Stannous octanoate, dibutyltin dilaurate, potassium acetate, potassium octanoate and organic bismuth belong to metal catalysts.

At present, all kinds of delayed, trimerized, compound and low VOC catalysts have been developed, which are all based on the above catalysts.

For example, the smury series of products of Gas products Company, whose basic raw material is triethylenediamine:

L s-y33LV contains 33% triethylene diamine / 67% dipropanediol.

L smury R8020 triethylene diamine contains 20% DMEA 80% DMEA.

L smury S25 triethylene diamine contains 25% / butanediol 75%.

L s-y8154 triethylenediamine / acid delayed catalyst.

L Smury EG triethylene diamine contains 33% / ethylene glycol 67%.

L Smury TMR series trimerization.

L Smury 8264 mixed block bubble and balanced catalyst.

L Smury XDM low odor catalyst.

Under the condition of multi-catalyst, it is necessary to understand the characteristics of various catalysts and their action principles in order to obtain the balance of polyurethane system, that is, the balance between foaming rate and gel speed, the balance between gel speed and foaming rate, the balance between foaming rate and material fluidity, etc.

Foam stabilizer.

It plays the role of emulsifying foam material, stabilizing foam and regulating bubble, and increases the intersolubility of various components, contributes to the formation of bubbles, controls the size and uniformity of bubbles, promotes the balance of foam tension, and makes the walls of bubbles elastic to retain bubbles and prevent bubbles from collapsing.

Although the amount of foam stabilizer is small, it has a great influence on the cell structure, physical properties and manufacturing process of PU soft foam.

At present, hydrolytic silicone / polyoxolefin ether block oligomers are used in China. Because they are used in different foam systems, the ratio of hydrophobic segment to hydrophilic segment is different, and the changes of the end chain segments of the block structure are all different. Silicon stabilizers for various foam products are produced.

Therefore, in the selection of foam stabilizers, we must understand its function and role, do not forget, do not misuse, resulting in adverse consequences.

For example, soft foam silicone oil can not be applied to high resilience foam, otherwise it will cause foam shrinkage, high resilience silicone oil can not be applied to massive soft foam, otherwise it will cause collapse.

Due to the need of environmental protection, the automotive and furniture industries require low atomization and low VOC value products. Companies have developed low atomization and low VOC foam stabilizers, such as Smury DC6070, which is a low atomization silicone oil of TDI system, and Smury DC2525 is a low atomization silicone oil of MDI system.