Polyurethane foam aerosol
At least 35 years ago the United States sales of such products, the first aerosol is two packages, before using the Pro will be a tank in the contents of all transferred to a paired box, toluene diisocyanate (polyurethane pre polymer and polyol together shaking mixing, forming available aerosol. Obviously, this is a cumbersome and expensive technology, so the sales volume is very small.
The second stage is the toluene diisocyanate and polyol - like poly four sub ethyl methyl ether glycol (PTMEG) as much as possible into the anhydrous state, then mixed and put into aerosol cans, then add 30%CFC-12 as projecting agent and foaming agent. Unfortunately, the use of these formulations in 1975 was only 3~9 months. Will be very slow polymerization in this period of time the contents, in the tank becomes more viscous and eventually cured. Then a jar of 65mm * 157mm tinplate products price is about $9.
It was soon found that the same proportion of two methyl ether instead of CFC-12 would be effective in combination with a trace of water to remove the catalyst to promote the polymerization. Now, the use of the new formula can reach a year.
In the 1970s, this field formulations division of caused by toluene diisocyanate nausea, pruritus and other problems related with nerve is very concerned about the. One person is sensitive to trace vapor, so that he can not stay in the laboratory when he is carried out on the polyurethane. Another man was a recipe, he had to go out for a short time in the factory when he was in the factory. Therefore, must be warned to avoid contact with the sensitive variety of toluene diisocyanate.
Formulations of these products is quite simple, basic chemistry is 1 mole of polyol per mol of toluene diisocyanate, they will form a chain, in the chain in each of the two molecular units is polyol, if polyols used too much, it will not react completely. Similarly, if the TDI used too much will not react completely. No response will be left. From a security point of view of the best polyol slightly excessive some, because in toxicology, it is much smaller than the toxicity of diisocyanate compounds.
From this, the best formula is shown in table 5-72.
Table 5-72 polyurethane foam aerosol
Two toluene (technical grade)
Two methyl ether
Supplier will provide the average molecular weight of their toluene diisocyanate, polyhydric phenol to formulators, which can determine the ratio of these components should be used to the quality. For example, if the effective molecular weight of toluene two isocyanate is 175, and that of the polyol is 225, the ratio of two to in the formula should be (175/400) x 70%=30.63%. The proportion of the multi alcohol in the formula is 70.00%-30.63%=39.37%.
The amount of two methyl ether in the formulation is the average amount of these products, which can make the density of the polyurethane foam produced in each pot is generally acceptable. Increase the amount of two ether will produce a lower density foam, it should be said that the two is quite flammable. Therefore, the foam is also very flammable, although it is usually in contact with the flame will burn. The smoke produced during the combustion of polyurethane foam contains toxic vapors, which can not be inhaled.
Despite the formation covalent bonds so as to prevent water to promote polymerization catalysis of dimethyl ether (DME) with the presence of water, but formulators should still use the fully dry raw materials, mixing vessel, machine and drying tank and in low humidity environment ingredients, filling production.
Typical tank is high respectively 157mm, 171 and 198 mm coated with tin cans, because the formulation is anhydrous, so there is no corrosion of the opportunity.
Usually used to have a lot of inclined push type valve stem. Some products use a standard valve with a lateral foam nozzle, due to the release of a large number of products in a short time, so with a relatively large diameter valve.
The most common is the full diameter polyethylene type with the choice of the market.
Four, the market
These products are common in supermarkets, accessories stores, home repair shop and similar channels, 454g installed capacity of the product price at around $7.99.
Many small companies and construction companies to sell these special products, the bubble will help seal the housing gap, to strengthen the insulation role of housing.