In packaging

Adipic acid is shipped in quantities ranging from 22.7 kg (50-lb bags) to 90.9 t (200,000-lb hopper cars). Upon long standing, the soHd material tends to cake, dependent on such factors as initial particle size and moisture content. Shipping data in the United States are "Adipic Acid," DOT-ID ALT 9077, DOT Hazard Class ORM-E. It is regulated only in packages of 2.3 t (5,000 lb) or more (hopper cars and pressure-differential cars and tmcks) (157). 

Gas-phase adsorption can also be used when regenerating the adsorbent is not practical. Most of these appHcations are used where the faciHties to effect a regeneration are not justified by the small amount of adsorbent in a single unit. Nonregenerative adsorbents are used in packaging, dual-pane windows, odor removal, and toxic chemical protection. 

The clean, durable, nondust-forrning character of polyethylene foam has led to its acceptance in packaging missile parts (230). Polyethylene foam sheet has also displaced polystyrene foam sheet for packaging glass bottles and containers because of its greater resUiency and tear resistance. 

Concern for personnel exposure to hydrazine has led to several innovations in packaging to minimize direct contact with hydrazine, eg, Olin s E-Z dmm systems. Carbohydrazide was introduced into this market for the same reason it is a soHd derivative of hydrazine, considered safer to handle because of its low vapor pressure. It hydrolyzes to release free hydrazine at elevated temperatures in the boiler. It is, however, fairly expensive and contributes to dissolved soHds (carbonates) in the water (193). In field tests, catalyzed hydrazine outperformed both hydrazine and carbohydrazide when the feedwater oxygen and iron levels were critical (194). A pubUshed comparison is available (195) of these and other proposed oxygen scavengers, eg, diethyUiydroxylarnine, ydroquinone, methyethylketoxime, and isoascorbic acid. 

In addition to these uses related to crop production, hydrocarbons are used extensively in packaging, particularly in plastic films and to coat boxes with plastic and (to a much lesser extent) wax. Polymeric resins derived from hydrocarbons are also used to make trays and cases for deflvery of packaged foodstuffs (see Eilmand sheeting materials Packaging Paper). 

The greatest amount of surfactant consumption is in packaged soaps and detergents for household and industrial use. The remainder is used in processing textiles and leather, in ore flotation and oil-drilling operations, and in the manufacture of agricultural sprays, cosmetics, elastomers, food, lubricants, paint, pharmaceuticals, and a host of other products. 

Of the estimated 710,000 t consumed in 1990, 25% was used to produce vinyl chloride [75-01-4] monomer (VCM), 14% for vinyl acetate [108-05-4] monomer (VAM), 23% for butanediol, 14% for industrial use, and the balance to produce other products such as acryUc acid, synthetic mbber, chlorinated solvents, and acetylene black. The demand for PVC is expected to decrease as legislation limiting its use in packaging is pending. Consequentiy, VCM consumption will also suffer. 

Purple Pigments. Methyl violet is the most commonly used purple pigment. It is also widely used for toning black inks. In packaging, although very expensive, Carbazole and Vat violets are used where permanence and resistance properties are needed. 

The objective in packaging cool sterilized products is to maintain the product under aseptic conditions, to sterilize the container and its Hd, and to place the product into the container and seal it without contamination. Contamination of the head space between the product and closure is avoided by the use of superheated steam, maintaining a high internal pressure, spraying the container surface with a bactericide such as chlorine, irradiation with a bactericidal lamp, or filling the space with an inert sterile gas such as nitrogen. 

LDPE is nontoxic, and is commonly used in food packaging (qv) where Food and Dmg Administration requirements, such as 21CFR in the case of thin films, must be met. It is also used in packaging pharmaceuticals and other medical appHcations such as iv bags and tubes. 

In the words of RSPA, the changes to the regulations will (/) simplify and reduce the volume of the HMR, 2) enhance safety through better classification and packaging, (3) promote flexibiUty and technological innovation in packaging, (4) reduce the need for exemptions from the HMR, and (5) facihtate international commerce (3). 

Because of the capacity to tailor select polymer properties by varying the ratio of two or more components, copolymers have found significant commercial appHcation in several product areas. In fiber-spinning, ie, with copolymers such as nylon-6 in nylon-6,6 or the reverse, where the second component is present in low (<10%) concentration, as well as in other comonomers with nylon-6,6 or nylon-6, the copolymers are often used to control the effect of sphemUtes by decreasing their number and probably their size and the rate of crystallization (190). At higher ratios, the semicrystalline polyamides become optically clear, amorphous polymers which find appHcations in packaging and barrier resins markets (191). 

Propylene Glycol. Propylene glycol, the second largest use of propylene oxide, is produced by hydrolysis of the oxide with water. Propylene glycol has very low toxicity and is, therefore, used direcdy in foods, pharmaceuticals (qv), and cosmetics, and indirectly in packaging materials (qv). Propylene glycol also finds use as an intermediate for numerous chemicals, in hydrauhc fluids (qv), in heat-transfer fluids (antifreeze), and in many other apphcations (273). 

Carboxylic Acid Group. Sorbic acid undergoes the normal acid reactions forming salts, esters, amides, and acid chlorides. Industrially, the most important compound is the potassium salt because of stabiUty and high water solubiUty. Sodium sorbate [7757-81-5] (E,E form [42788-83-0]) is less stable and not commercially available. The calcium salt [7492-55-9] which has limited solubiUty, has use in packaging (qv) materials. 

Cotton yam is dyed in package machines and the dye exhausted by increasing the temperature and adding salt. The dye must be completely dissolved when preparing the dyebaths to avoid contamination with undissolved dye in the yam package. The increased avaUabUity of the prereduced Hquid dyes and the improved quaHty of sodium sulfide have reduced this problem. Incorrectly dissolved dye was previously the cause of most faulty dyeings. 

Miscellaneous Uses. Inks used by inspectors to stamp the grade or quaUty on meat must, bylaw, be made from food-grade colors. Dyes used in packaging materials that come in direct contact with a food must also be food-grade or, if not, it must be estabUshed that no part of the colorant used migrates into the food product. Pet foods, too, if colored, must contain only those colorants recognized by the FDA as suitable for the purpose. 

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