HEC

The commeicialization of new watei-soluble polymers is most often a slow process. Eor example, hydroxyethylceUulose (HEC) was envisaged in 1937 by... 

A. E. Broderick (Union Carbide). HEC did not become a viable commercial product until the early 1960s. In addition to the general production problems and market development costs, new products face a variety of environmental controls in the 1990s that add more constraints to market development. None the less two more recentiy developed water-soluble polymers have achieved limited market acceptance and are described below. 

The development of high fmctose com symp (HECS) may provide another health benefit attributable to cereal grains (see Syrups). These symps are being used to an ever-increasing extent by the food industry. Shortly after HECS came on the market, a dramatic increase in the price of sucrose acted as a spur to the production of the high fmctose symps. 

I. G. Ryss, The Chemistry of Fluorine and Its Inorganic Compounds., State Publishing House for Scientific and Technical Literature, Moscow, 1956 Engl. transL by E. Haimson for the U.S. Atomic Energy Commission,HEC-/r-i5 27, Washington, D.C., 1960, p. 812. 

Properties. The physical properties of aHphatic fluorine compounds containing chlorine are similar to those of the PECs or HECs (3,5). They usually have high densities and low boiling points, viscosities, and surface tensions. The irregularity in the boiling points of the fluorinated methanes, however, does not appear in the chlorofluorocarbons. Their boiling points consistently increase with the number of chlorines present. The properties of some CECs and HCECs are shown in Tables 3 and 4. 

HEC hydroxyethyl cellulose nonionic 110 viscosity builder, acid degradable primarily for completion/workover fluids... 

Sodium carboxymethyl cellulose [9004-32-4] (CMC) and hydroxyethyl cellulose [9004-62-0] (HEC) are the ceUulosics most widely used in drilling fluids (43). CMC is manufactured by carboxymethylation of cellulose which changes the water-insoluble cellulose into the water-soluble CMC (44). Hydroxyethyl cellulose and carboxymethyl hydroxyethyl cellulose (CMHEC) are made by a similar process. The viscosity grade of the material is determined by the degree of substitution and the molecular weight of the finished product. 

Hydroxyethyl cellulose (HEC), a nonionic thickening agent, is prepared from alkali cellulose and ethylene oxide in the presence of isopropyl alcohol (46). HEC is used in drilling muds, but more commonly in completion fluids where its acid-degradable nature is advantageous. Magnesium oxide stabilizes the viscosity-building action of HEC in salt brines up to 135°C (47). HEC concentrations are ca 0.6—6 kg/m (0.2—21b/bbl). 

Although not designed to control filtration, HEC may be effective as a filtration control agent in combination with other organic polymers in waters having salinities up to saturation. 

Hydroxyethyl- andHydroxypropylcelluloses. HydroxyalkylceUuloses are ceUulose ethers prepared by reaction of alkaU ceUulose with ethylene oxide, to prepare hydroxyethjlceUulose (HEC) [9004-62-0] or propylene oxide, to prepare hydroxypropylceUulose (HPC) [9004-64-2]. 

In general, the MS controls the solubUity of both HEC and HPC. Eor example, water-soluble grades of hydroxyethylceUulose have MS values of 1.6—3.0 those with MS 0.3—1.0 are soluble in aqueous alkaU. Even higher MS types of hydroxypropylceUulose become soluble in organic solvents, first polar, then nonpolar solvents. 

Properties. HydroxyethjIceUulose [9004-62-0] (HEC), is a nonionic polymer. Low hydroxyethyl substitutions (MS = 0.05-0.5) yield products that are soluble only in aqueous alkali. Higher substitutions (MS > 1.5) produce water-soluble HEC. The bulk of commercial HEC falls into the latter category. Water-soluble HEC is widely used because of its broad compatibiUty with cations and the lack of a solution gel or precipitation point in water up to the boiling point. The MS of commercial HEC varies from about 1.8 to 3.5. The products are soluble in hot and cold water but insoluble in hydrocarbon solvents. HEC swells or becomes pardy to mosdy soluble in select polar solvents, usually those that are miscible with water. 

Commercially, HEC is available in a wide range of viscosity grades, ranging from greater than 500 mPa-s(=cP) at 1% soHds to less than 100 mPa-s(=cP) at 5% total soHds. Because HEC is nonionic, it can be dissolved in many salt solutions that do not dissolve other water-soluble polymers. It is soluble in most 10% salt solutions and in many 50% (or saturated) salt solutions such as sodium chloride and aluminum nitrate. As a rule, the lower substitution grades are more salt-tolerant. 

Solutions of HEC are pseudoplastic. Newtonian rheology is approached by very dilute solutions as well as by lower molecular-weight products. Viscosities change Httie between pH 2 and 12, but are affected by acid hydrolysis or alkaline oxidation under pH and temperature extremes. Viscosities of HEC solutions change reversibly with temperature, increasing when cooled and decreasing when warmed. 

HEC is generally compatible with other ceUulosic water-soluble polymers to give clear, homogeneous solutions. When mixed with an anionic polymer such as CMC, however, interactions between the two polymers may result in synergistic behavior, ie, viscosities higher than predicted and calculated. HEC has excellent compatibiUty with natural gums. 

Because of the low boiling point of ethylene oxide, reactions are generally conducted in stirred autoclaves at elevated pressures. Economic Aspects. A breakdown of saUent 1987 world supply and demand figures for HEC is given in Table 5. 

Aqualon Co. and Union Carbide Corp. have manufacturing faciUties in the United States and Western Europe. Hoechst AG in Europe and Euji Chemical Co., Ltd. inJapan are the only other procedures of HEC. 

Specifications and Standards Test Methods. Hydroxyethylcellulose is included in the Hst of materials that are in compHance with requirements of the U.S. EDA for use in adhesives and in resinous and polymeric coatings employed on the food-contact surfaces of metal, paper, or paperboard articles, and other substrates intended for use in food packaging as specified in CER 21. HEC made dispersible by cross-linking with glyoxal is cleared only as an adhesive and as a component of paper and paperboard in contact with food. It has not been cleared as a direct food additive. 

Uses. HEC is used as a thickener, protective coUoid, binder, stabilizer, and suspending agent in a variety of industrial appHcations. A guide to the principal uses is given in Table 6. 

Mixed Ether Derivatives of HEC. Several chemical modifications of HEC are commercially available. The secondary substituent is generally of low DS (or MS), and its function is to impart a desirable property lacking in HEC. 

Table 7. Typical Properties of Mixed Ether Derivatives of HEC ...

Cationic Hydroxyethylcelluloses. These materials are manufactured by Union Carbide Corp. and National Starch and Chemical Corp., marketed under the trade names Polymer JR and Celquat, respectively (47,48). The cationic substituent on Polymer JR is presumably 2-hydroxypropyltrimethylammonium chloride (72). Celquat is presumably the reaction product of HEC with /V,/V-dia11y1-/V,/V-dimethy1ammonium chloride (73). Their primary appHcation is in shampoos and hair conditioners wherein the cationic moiety imparts substantivity to hair. Some typical properties of Celquat resins are given in Table 7. 

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