This is particularly true when the compounds vi are built into the polyurethane network being formed as a result of the presence of groups such as OH or NH 2 capable of being incorporated into the polyurethane structure. Varying the proportion of these polyols allows the open cell content of PUR foams to be set in a targeted manner. Suitable solvents or diluents are hydrocarbons substances, in particular Toluot ketone xylene or cyclohexane, esters, particularly ethyl glycol acetate, ethyl acetate or butyl acetate, amides, especially dimethylformamide or N-methylpyrrolidone, sulfoxides, particularly dimethyl sulfoxide, ketones, particularly methyl ethyl ketone or cyclohexanone, ethers, in particular diisopropyl ether or methyl tert. Taking Rf values during the performance of the experiment helps track the progress of the reaction and determine the ending point of reaction. Once the solid has completely dissolved, cool the solution in an ice water bath to promote crystallization. The IR spectrum indicates the presence of the desired product.
The modified polyisocyanates can, together or with unmodified organic polyisocyanates such. The polyurethane foams can be prepared by the known prepolymer process, for example with the aid of high-pressure or low-pressure technique, in open or closed molds, reaction extruders or belt systems, for example, by the one-shot method, or the like.
In particular, tertiary Aminkata catalysts having reactive functional groups such as OH and NH 2 accelerate the amine formation by lowering the activa approximately energy for the cleavage reaction considerably. The same applies to formulations containing polyols with primary or secondary amines as Start - were produced molecules and thus catalytic activity present in the foam. Im einzelnen kommen beispielsweise in Betracht: Urethangruppen enthaltende organische, vorzugsweise aromatische Polyisocyanate mit NCO- Gehalten von 33,6 bis 15 Gew. In the case of polyisocyanate polyaddition products, for example polyurethanes, hereinafter also referred to as PURs, especially the action of moisture and even more the combination of moisture and elevated temperature results in hydrolytic cleavage of the urethane and urea bonds.
Here, the usual, used to prevent thermal polymerization of compounds, for example of the type of hydroquinone, the Hydrochinorunonoalkylether come, the 2,6-di- tert. The addition of the inhibitors reduces the hydrolysis of urethane and urea bonds in two ways: as mentioned by deactivating the amine catalysts present and also as a result of a major part of the water which penetrates being consumed in the hydrolysis of the lactones and lactams added and no longer being available for the cleavage of urethane and urea bonds. These additives should have no significant effect on the foaming reaction and the properties of the foams. Organic Chemistry 6th ed. In addition, the metal salts can act as oxidation catalysts and accelerate oxidative degradation of any aromatic amines formed. Enichem , sowie Mischungen solcher Verbindungen in Betracht kommen.
The same applies to formulations with polyols prepared with primary or secondary amines as starting molecules and thus catalytic activity present in the foam. However, the catalytic effect of additives to reduce the amine content in the finished PUR foams is undesirable as this above be enrolled leads to a further and accelerated formation of primary amines. Advanced Organic Chemistry 5th ed. Keep the vacuum filtration on for an additional 10 minutes to help air dry the solid. Here, the usual, used to prevent thermal polymerization of compounds, such.
BASF Fa. The compound A from the reaction mixture by known methods, eg. However, the improvement in the hydrolysis resistance increased hardness, tensile strength and elongation at break is restricted to polyurethane elastomers containing polyesters as polyol component. The IR spectrum indicates the presence of the desired product. These isocyanates react owing to their steric hindrance and reduced compared to aromatic isocyanates reac tivity during the foaming reaction from only a small extent, so that after completion of the foaming reaction to free isocyanate reac tion communicates with optionally present aromatic amines to Ver addition. The diffusion or migration of primary amines out of the polyurethane foams can thus be reduced according to the present invention.
Draw the structure of the cis and trans isomers of the compound that you prepared. Examples which may be mentioned are hydroxyethyl acrylate and 3- acryloyloxy hydroxypropyl methacrylate. The polyurethane foams obtainable according to have the particular advantage that, if appropriate, formed by hydrolysis, primary amines, in particular primary aromatic amines, by the compounds i into a harmless form are transferred. Draw the mechanism for the formation of the product.
In addition, these isocyanates tend to migrate out of the finished foam because of their low vapor pressure and thus pose a further health hazard due to the occurrence of free isocyanate. The modified polyisocyanates can, together or with unmodified organic polyisocyanates such. In particular, additives should be invented, which are able to reduce the content of primary, preferably primary aromatic amines in polyurethane foams. The method is characterised in that the reaction is carried out in the presence of at least one of the following compounds i : alpha , beta -unsaturated carboxylic acid, alpha , beta -unsaturated carboxylic acid derivative, alpha , beta -unsaturated ketone and or alpha , beta -unsaturated aldehyde. The method according to claim 1, characterized in that i , are used in an amount of 0. Crystallization was slow and crystals Use a seed crystal; A sample of pure failed to appear after 15 minutes.
The hydrophobic compounds used according to the present invention do not pose a health hazard and can be easily incorporated into the polyol component because of their good compatibility with the constituents of the polyol component. The amine scavenger should be as inexpensive and readily available and should be able to exert their effect in the finished foam without further treatment. In hydrolyzed form, sultones improve the fogging behavior by preventing diffusion of tertiary amine catalysts as a result of the reaction of these with the hydrolyzed sultones. The starting materials for the production of polyurethane foams have been described as an example. Stir the solution with the glass stirring rod for 5 minutes.
In addition, the metal salts can act as oxidation catalysts and accelerate oxidative degradation of any aromatic amines formed. In a medium size tube, mix 2mL of benzaldehyde with 15 drops of acetone, and leave it at room temperature for 5 minutes. Step 3: An acid-base reaction. A disadvantage of these compounds is their catalytic action which has an adverse effect on the foaming reaction. Alkylene oxides are preferably used which lead to primary hydroxyl groups in the polyol. Part II Recrystallization
Write a complete reaction to support your result. Organic Chemistry 6th ed.