Urea plastics resins

Urea is also used as feed supplement for mminants, where it assists in the utilization of protein. Urea is one of the raw materials for urea—formaldehyde resins. Urea (with ammonia) pyrolyzes at high temperature and pressure to form melamine plastics (see also Cyanamides). Urea is used in the preparation of lysine, an amino acid widely used in poultry feed (see Amino acids Feeds and feed additives, petfoods). It also is used in some pesticides. 

Amino and Phenolic Resins. The largest use of formaldehyde is in the manufacture of urea—formaldehyde, phenol—formaldehyde, and melamine—formaldehyde resins, accounting for over one-half (51%) of the total demand (115). These resins find use as adhesives for binding wood products that comprise particle board, fiber board, and plywood. Plywood is the largest market for phenol—formaldehyde resins particle board is the largest for urea—formaldehyde resins. Under certain conditions, urea—formaldehyde resins may release formaldehyde that has been alleged to create health or environmental problems (see Amino RESINS AND PLASTICS). 

Formaldehyde. Worldwide, the largest amount of formaldehyde (qv) is consumed in the production of urea—formaldehyde resins, the primary end use of which is found in building products such as plywood and particle board (see Amino resins and plastics). The demand for these resins, and consequently methanol, is greatly influenced by housing demand. In the United States, the greatest market share for formaldehyde is again in the constmction industry. However, a fast-growing market for formaldehyde can be found in the production of acetylenic chemicals, which is driven by the demand for 1,4-butanediol and its subsequent downstream product, spandex fibers (see Fibers, elastomeric). 

In the eady 1920s, experimentation with urea—formaldehyde resins [9011-05-6] in Germany (4) and Austria (5,6) led to the discovery that these resins might be cast into beautiful clear transparent sheets, and it was proposed that this new synthetic material might serve as an organic glass (5,6). In fact, an experimental product called PoUopas was introduced, but lack of sufficient water resistance prevented commercialization. Melamine—formaldehyde resin [9003-08-1] does have better water resistance but the market for synthetic glass was taken over by new thermoplastic materials such as polystyrene and poly(methyl methacrylate) (see Methacrylic polya rs Styrene plastics). 

Chemical compounds manufactured at petrochemical plants include methanol, formaldehyde, and halogenated hydrocarbons. Formaldehyde is used in the manufacture of plastic resins, including phenolic, urea, and melamine resins. Halogenated hydrocarbons are used in the manufacture of silicone, solvents, refrigerants, and degreasing agents. 

Urea plastics Group of plastics whose resins are derived from the condensation of urea and aldehydes. 

EICEIO, a gas with an irritating smell. It is made industrially by the oxidation of methyl alcohol, and is used in the manufacture of phenol-formaldehyde and urea-formaldehyde resins and plastics. 

Table 12.3 summarizes the uses of formaldehyde. Two important thermosetting plastics, urea- and phenol-copolymers, take nearly one half the formaldehyde manufactured. Urea-formaldehyde resins are used in particleboard, phenol-formaldehyde resins in plywood. 1,4-Butanediol is made for some polyesters and is an example of acetylene chemistry that has not yet been replaced. Tetrahydrofiiran (THF) is a common solvent that is made by dehydration of 1,4-butanediol. 

Sylplast Urea-formaldehyde resins Sylvan Plastics... 

For the preparation of the foam, a solution of 1 g technical sodium diisobutyl naphthalene sulfonate in 50 ml of 3% orthophosphoric acid is prepared. 20 ml of this solution are poured into a 11 beaker and air is stirred in with a fast running mixer until the cream-like dispersion has reached a volume of 300-400 ml.Then,20 ml of the prepared urea/formaldehyde resin are mixed in, whereby the resin must be evenly distributed. After 3-4 min the introduced resin gellifies into a molded article permeated with many water/air pores under the influence of the acidic catalyst. After 24 h,the crosslinking is completed. Drying for 12 h at 40 °C in a circulating air dryer yields a brittle thermoset foam.The foamed plastic obtained is hydrophobic and has a large internal surface. It can take up about 30 times its own weight of petroleum ether. 

Another use of urea is for resins, which are used in numerous applications including plastics, adhesives, moldings, laminates, plywood, particleboard, textiles, and coatings. Resins are organic liquid substances exuded from plants that harden on exposure to air. The term now includes numerous synthetically produced resins. Urea resins are thermosetting, which means they harden when heated, often with the aid of a catalyst. The polymerization of urea and formaldehyde produces urea-formaldehyde resins, which is the second most abundant use of urea. Urea is dehydrated to melamine, which, when combined with formaldehyde, produces melamine-formaldehyde resins (Figure 96.2). Melamine resins tend to be harder and more heat-resistant than urea-formaldehyde resins. Melamine received widespread attention as the primary pet food and animal feed contaminant causing numerous cat and dog deaths in early... 

Sand cores -Urea-formaldehyde resins [AMINO RESINS AND PLASTICS] (Vol 2)... 

UREA-FORMALDEHYDE RESIN. An important class of amino resin. Urea and formaldehyde are united in a two-stage process in the presence of pyridine, ammonia, or certain alcohols with heat and control of pH to form intermediates (methylolurea, dimenthylolurea) that are mixed with fillers to produce molding powders. These are converted to thermosetting resins by further controlled heating and pressure in the presence of catalysts. These were first plastics that could be made in white, pastel, and colored products. See also Amino Acids Melamine. 

Plastics, Metals, and Ceramics A Comparison thermosetting plastic or duroplastic, e.g. urea-formaldehyde resin (UF) ... 

With urea, formaldehyde forms two stable IV.O-hemiacetals (Figure 9.25) a 1 1 adduct ( methylol urea ) and a 1 2 adduct ( dimethylol urea ). When they are heated, both compounds are converted to macromolecular IV.lV-acetals (Figure 9.26). A three-dimensionally cross linked urea/formaldehyde resin is produced it is an important plastic. 

The use of sorbitol in enhancing the clarity of urea-formaldehyde resins is described in a patent (30) as is also its use with inorganic materials to form useful plastics (31). A dianhydride of sorbitol is described as a humectant for tobacco (34). The main industrial studies of Goepp were concerned with the use of sorbitol and D-mannitol in the manufacture of resins of the ester gum (esters with rosin acids) or alkyd (linseed oil-phthalic anhydride-hexitol) types (32, 14). It was shown that in the preparation of these polyesters the behavior of the hexitols is... 

Urea reacts with formaldehyde to form the urea-formahlehyde resins, highly important in molded plastics. Here, too, a space-network polymer is formed. 

The principal end use of urea is to provide combined nitrogen for solid fertilizer formulations. Some urea is also converted to biuret (H2NCONHCONH2, also called carbamoyl urea) and to a sulfur derivative, which are sold as Kedlor [65] and Urasil [66] cattle feed supplements, respectively. Urea is also used to a lesser extent in the manufacture of plastics components, such as melamine, and as a component of urea-formaldehyde resins used as adhesives. It is also used as a component of foam-in-place formulations as a rigid insulating material [67], and as an ingredient in noncorrosive aircraft deicing solutions [67a]. 

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