GELLING

Dihydroxybutane. -butylene glycol, CH3CH(0H)CH2CH20H, b.p. 204°C. Manufactured by reduction of aldol or by the action of yeast on aldol. Used to prepare butadiene. Used in brake fluids, in gelling agents and as an intermediate in plasticizers. 

Pectin also contains araban and galactan. Il is present in fruits, root vegetables and other plant products, and confers on jams their typical gelling property. Pectin is manufactured as a white powder, soluble in water, and used to assist the setting of jams and jellies, and for numerous other purposes. Low melhoxyl pectins, with under 7% methoxyl, give firmer gels than pectins proper. 

The selection of gelling agents and liquid lubricants is conducted according to the requirements for a specific use ... 

These properties are mainly associated with the gelling agent and liquid lubricant. 

The great number of possible associations between the types of liquid lubricants and gelling agents results in many different categories of greases ... 

Gellan m [71010-52-1] Gelling agent Gelling agents Gelling reaction... 

Polyurethane is pulverized to iacrease its bulk density, mixed with 30—80% of a thermoplastic mol ding material, gelled, and then granulated to give coated urethane foam particles 0.1 to 0.15 mm in size (48). The particle bulk density is three times that of the polyurethane, while the volume is 15% less. This material may be injection molded or extmsion molded into products (49). Other technologies for recycling polyurethanes have also been reported. 

The thin dispersion rapidly thickens into a gelled matrix and coagulates into a water-repellent agglomeration that doats on the aqueous medium as the mechanical agitation is continued. The agglomeration is dried gentiy shearing must be avoided. 

The earhest frothing process developed was the Dunlop process, which made use of chemical gelling agents, eg, sodium fluorosiUcate, to coagulate the mbber particles and deactivate the soaps. The Talalay process, developed later, employs freeze-coagulation of the mbber followed by deactivation of the soaps with carbon dioxide. The basic processes and a multitude of improvements are discussed extensively in Reference 3. A discussion more oriented to current use of these processes is given in Reference 115. 

Catalysis of the flexible polyurethane foaming operation is accompHshed through the use of tertiary amine compounds, often using two different amines to balance the blowing and gelling reactions. OrganometalHc compounds, usually staimous salts, are also used to faciHtate gelling and promote final cure. 

Box Foa.ms. A measured quantity of the reaction mixture can be placed ia an open-topped crate or box and allowed to foam ia a free rise mode. The block is removed after gelling and is cut iato end use pieces after curiag. 

The Vanderbilt process involves the mechanical frothing of air into a plastisol containing proprietary surfactants by means of an Oakes foamer or a Hobart-type batch whip. The resulting stable froth is spread or molded in its final form, then gelled and fused under controlled heat. The fused product is open-ceUed with fine cell size and density as low as 160 kg/m (10 lbs/fT). 

---