Resins Containing Thiourea

Such condensation reactions occur on mixing the two components. The resultant comparative intractability of the material is one of the main reasons for its industrial eclipse. 

Some typical properties of aniline-formaldehyde mouldings are given in Table 24.2. 

Specific gravity Rockwell hardness Water absorption (24 h) 

Tensile strength Impact strength Dielectric constant Power factor 100 Hz IMHz 100 MHz 

Resistant to alkalis, most organic solvents Attacked by acids 

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The term aminoplastics has been coined to cover a range of resinous polymers produced by interaction of amines or amides with aldehydes. Of the various polymers of this type that have been produced there are two of current commercial importance in the field of plastics, the urea-formaldehyde and the melamine-formaldehyde resins. There has in the past also been some commercial interest in aniline-formaldehyde resins and in systems containing thiourea but today these are of little or no importance. Melamine-phenol-formaldehyde resins have also been introduced for use in moulding powders, and benzoguanamine-based resins are used for surface coating applications. 

The fuUy automated, sequential flow-through synthesis of a 44-member array of thioethers via a resin capture-and-release reactor column was performed in our laboratory. Each of the acidic heterocycles (49-52) containing thiourea moieties were deprotonated by the use of a strong polymer-supported base, such as 1,5,7-triazabicyclo[4.4.0]dec-5-ene polystyrene (PS-TBD) to generate an immobilised ionic complex on the column (Figure 12). 

Alternatively, we prefer to prepare polymers containing the thiol functionally (15,25) by reacting chloromethylated resin with thiourea (25). The reaction of y-CI Cl with thiourea gives a supported isothiouromium chloride. The latter solid is reacted with hydroxyl groups to produce a thiol-containing polymer. 

Urea-formaldehyde reaction products were described as early as 1908, but the first useful commercial product, a molding compound invented in England by Edmond C. Rossiter, did not arrive until almost 20 years later. It was a fairly complex formulation using purified cellulose fiber as reinforcement. The amino resin contained equimolar amounts of urea and thiourea. The new product could be supplied in light translucent colors. The molded products had a hard, stain resistant surface, and there was no objectionable phenolic odor. In short, the product was unique for its time. 

At one time thiourea-urea-formaldehyde resins were of importance for moulding powders and laminating resins because of their improved water resistance. They have now been almost completely superseded by melamine-formaldehyde resins with their superior water resistance. It is, however, understood that a small amount of thiourea-containing resin is still used in the manufacture of decorative laminates. 

Remove unreacted N-acetyl homocysteine thiolactone and reaction by-products by gel filtration or dialysis against lOmM sodium phosphate, 0.15M NaCl, lOmM EDTA, pH 7.2. Other buffers suitable for individual protein stability may be used as desired. For the silver nitrate-containing reaction, removal of the silver-thiourea complex may be done by adsorption onto Dowex 50, and the protein subsequently eluted from the resin by 1M thiourea. Removal of the thiourea then may be done by gel filtration or dialysis. 

After the optimization of these conditions, by adding an azide to the input stream it was possible to synthesize a range of substituted triazoles in a heterogeneously catalysed three-component reaction (Scheme 18). After the CFC, the stream was passed through a column containing a resin-immobilized copper-based catalyst, which was used in a previous work by the same authors to successfully catalyze the formation of triazoles from alkynes and azides [44]. An immobilized thiourea-containing cartridge was subsequently used to remove any leached Cu catalyst. In a similar way as for the alkynes production, the series of resins was used to purify the product. 

In this study, two Deloxan Metal Scavengers were investigated. The first, THP II, is a thiourea functionalized polysiloxane while the second, MP, is mercapto functionalized. Both resins have been tested in solutions containing 20 - 100 ppm Pd(II), Pd(0) or Ru(II). In addition to different metals and oxidation states, the effects of solvent (polar vs. nonpolar), temperature (25 - 80 °C) and mode (fixed bed vs. batch) were explored. These resins were found to reduce precious metal concentrations in process solutions to levels at or below the target concentration of 5 ppm, even at room temperature in the case of Pd(II) and Pd(0). The results of this study will be discussed. 

Amino-aldehyde resin blasting compn containing gaseous voids. An example is thiourea 10, sodium nitrate 10, AN 30, powdered Al 2Vi, yi7o aq formaldehyde 10 parts, adjusted to sp gr 1.17 with glass microspheres)... 

Macroreticular polystyrene-based resins with functional aminothiazole, imino-thiazole, or thiazoline groups exhibit a high selectivity for mercury(II). A thiazoline resin column has been used to concentrate mercury from sea water adjusted to pH 1 with hydrochloric acid. Maximum sorption capacity for mercury was found to be 2.8 mmole/g. The sorbed mercury is recovered quantitatively by eluting with 0.1 M HC1 containing 5 % thiourea 100). 

At about this time we became aware of a new product from Degussa, a macroporous organofunctional polysiloxane chemically bonded thiourea (DELOXAN) THP that had a high affinity to precious and heavy metals. The manufacturer claimed that the use of the resin, either in suspension or in a fixed-bed, resulted in removal of metals from aqueous or organic solutions. When a small amount of the Deloxan resin was added to the filtered hydrogenation solution containing high amounts of colloidal palladium, stirred and filtered, the palladium content of the filtrate dropped well below the 10 ppm level (Table II). 

Thiol and thiourea containing polymeric media (Figure 9.5) are highly effective in removing ruthenium, as well as tin, metal ions. These can reduce the concentration of ruthenium and tin metal species to less than 1 ppm after just one pass through the resin bed. 

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