Slow rebound spongeThe formula is similar to that of ordinary sponge. In addition to the major differences in the main polyether materials, some minor materials can be used interchangeably. However, in order to produce high-quality products, the selection of small ingredients should still be carefully considered and selected.
1. Selection of amines
The most classic amine used for slow rebound sponges is Dabco33-LV from American Air Company. Its dosage is generally 0.3-0.8 parts of the total amount of polyether. It is formulated from 33% triethylenediamine and 67% dipropylene glycol (DPG). The reason why this product is recommended is that the solvent it uses is dipropylene glycol. Someone may ask, is a solvent so important? The answer is yes. Judging from the ability to dissolve triethylenediamine, there are many alcohol compounds that can be used as solvents: such as propylene glycol, diethylene glycol, ethylene glycol, 1.4-butanediol, etc., but only one of these small molecular alcohols Dipropylene glycol has the largest 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 weight alcohols can consume TDI. The result is: on the one hand, the TDI index is reduced, on the other hand It is easy to cause sponge obturation.
Before 2012, only a few countries in the world could produce DPG with a purity of more than 99%. Only one factory in Anhui Province in my country could produce DPG with a purity close to 95%. The purity difference was a few percentage points. Domestic DPG condensed at room temperature. It cannot be used as a solvent, thus limiting the localization of amine catalysts using DPG as a solvent. Therefore, the most widely supplied amines on the domestic market are amines formulated with ethylene glycol as solvent. Some catalyst manufacturers, in pursuit of profits, deliberately reduce the concentration of triethylenediamine. When using such an amine to foam, in order to ensure the catalytic ability, it is necessary to increase the amount of catalyst. This kind of catalyst containing a large amount of small molecule solvents will If too much TDI is consumed, if the TDI dosage is not adjusted, the sponge will become soft and the tendency of closed cells will increase. In addition, the slow rebound tension and tear strength emitted by this amine are not good.
I believe that with the advancement of domestic chemical separation engineering technology, more and more high-purity DPG will come out, and more and more domestic Dabco33-LV will be produced. Of course, some other amines can also produce slow rebound, such as 9727, CS90, etc. However, rigorous small tests must be done before use, and the amplification effect must be considered during production. It is not recommended to use SMP to send slow rebound. When foaming is difficult in winter, 0.1-0.3 parts of A1 catalyst can be added to strengthen the foaming reaction.
2. Selection of tin
Masters who have haired ordinary cotton like to use stannous octoate (T-9) to hair slow rebound, but the author recommends using dibutyltin dilaurate (D22, T-12, also called K-19 in China). Stannous octoate is suitable for hair sponges with medium and low density. Its characteristic is that it sticks quickly in the early stage but lacks stamina. It is used to make high-density sponges and has poor post-curing properties. T-9 is easy to hydrolyze, and the slow rebound itself has a slow onset (the onset time is generally controlled at about 160 seconds). If it is in contact with water for a long time, part of it will be hydrolyzed, which will affect the aging. Dibutyltin dilaurate does not hydrolyze, rises, gels, matures smoothly, and has good post-curing properties.
Some colleagues once said that the tensile strength of the sponge was not good. The author suggested using dibutyltin dilaurate. The feedback was that the tensile strength was improved. If using T-9, the dosage is 0.1-0.4 parts. If dibutyltin dilaurate is used, the dosage can be controlled between 0.03-0.05. If the assembly line rebounds slowly, the dosage can be reduced to 0.001-0.01 parts. For export orders that restrict the use of tin catalysts, the author suggests that bismuth naphthenate can be used instead of tin.
3. Selection of silicone oil
Typical slow rebound silicone oil is B8002, and its dosage is between 0.5-2 parts. Use high-density sponges sparingly and low-density sponges more. Use more for manual soaking and less for machine hair. In recent years, domestic silicone oil suppliers have developed a lot of silicone oils for slow rebound, and their performance is also good. L-580 is also used for slow rebound. At this time, the amount of silicone oil should be reduced. After all, the activity of L-580 is relatively high.
4. Selection of pore opening agents
The history, current situation, performance, and application of pore opening agents have been briefly described in previous articles, so I will not go into details here.
5. Flame retardants are also used in slow rebound sponges. Since there are not many such lists, we will not discuss them here.
6. The use of pigments is basically the same as ordinary cotton and can be skipped. Just be careful when encountering black cotton, because the carbon black used to prepare the black color paste is hydrophobic, which will affect the compatibility of the components in the formula and the efficiency of the catalyst. Many colleagues have encountered the phenomenon that black cotton is easy to crack. Here’s why. Therefore, when black sponge is produced, the amount of catalyst should be appropriately adjusted.
