Packings moisture

Polyurethanes are frequently used in anticorrosion coatings. The R D drive of most coatings and resin producers is the reduction of the solvent content of the paint and resin systems. One method of achieving the environmental aims demanded by legislation in the PU coatings industry is to use oxazolidines which are suitable as latent hardeners to enable production of single-pack moisture activated PUs. The isocyanate chosen for this research is tetramethylxylene diisocyanate, which has been available commercially only since 1988. 19 refs. 

From this it should be seen that if an aqueous product is stored in a permeable pack, moisture loss will relate to the external environment and whether it is static or is subject to motion or movement. Storage at, say, 37°C 90% RH will be relatively restrictive to moisture loss, whereas 37°C 30% RH will have a significantly greater gradient and losses could be relatively high (particularly if held in a venting cabinet with a fan). 

Dizinc orthosilicate EINECS 237-057-8 Silicic acid (H4Si04), zinc salt (1 2) Tomusil Willemite Zinc silicate. A proprietary two-pack moisture cured inorganic zinc silicate primer. Insoluble in H2O. Coatings Sigma. 

This type of finish is an extension of the one-pack moisture-curing type. It is virtually the same finish, to which a small quantity of catalyst is added just before use. Tertiary amines, such as N,N-dimethylethanolamine [HO CH2 CH2 N(CH3)2], are most frequently used as catalysts. Even if the moisture content of the air is low, the finish will harden rapidly, but the more reliable drying performance is obtained at the expense of a limited pot-life. Unfortunately, the activator is non-polymeric and so cannot be used for pigment dispersion. Pigments are dispersed in pre-polymer and must be free from moisture, as in the one-pack composition. The uncatalysed finish is water-sensitive, presenting a shelf-life storage problem as before. 

Butynediol soHd flakes are packed in polyethylene bags inside dmms. The product is hygroscopic and must be protected from moisture. 

Polyacrylamide powders are typically shipped in moisture-resistant bags or fiber packs. Emulsion and solution polymers are sold in dmms, tote bins, tank tmcks, and tank cars. The transportation of dry and solution products is not regulated in the United States by the Department of Transportation, but emulsions require a DOT NA 1693 label. 

Environmental Protection. Fumes resulting from exposure of anhydrous aluminum chloride to moisture are corrosive and acidic. Collection systems should be provided to conduct aluminum chloride dusts or gases to a scmbbing device. The choice of equipment, usually one of economics, ranges from simple packed-tower scmbbers to sophisticated high energy devices such as those of a Venturi design (11). 

High quahty SAMs of alkyltrichlorosilane derivatives are not simple to produce, mainly because of the need to carefully control the amount of water in solution (126,143,144). Whereas incomplete monolayers are formed in the absence of water (127,128), excess water results in facile polymerization in solution and polysiloxane deposition of the surface (133). Extraction of surface moisture, followed by OTS hydrolysis and subsequent surface adsorption, may be the mechanism of SAM formation (145). A moisture quantity of 0.15 mg/100 mL solvent has been suggested as the optimum condition for the formation of closely packed monolayers. X-ray photoelectron spectroscopy (xps) studies confirm the complete surface reaction of the —SiCl groups, upon the formation of a complete SAM (146). Infrared spectroscopy has been used to provide direct evidence for the hiU hydrolysis of methylchlorosilanes to methylsdanoles at the soHd/gas interface, by surface water on a hydrated siUca (147). 

A humidification subsystem controls the temperature, flow rate, and relative humidity of the sweep stream. Air and water can be fed to a Hquid-gas packed contactor to produce the desired moisture level ia the vapor stream. The saturation temperature controls the water loading of the air which can be heated to give exactly the desired relative humidity. 

Coffee vacuum-packed in flexible, bag-in-box packages has gained wide acceptance in Europe. The inner liner, usually a plastic-laminated foil, is formed into a hard brick shape during the vacuum process (30). In the United States, a printed multilaminated flexible stmcture is used to form the brick pack which is sold as is at retail. These types of packages provide a barrier to moisture and oxygen similar to that of a metal can. 

Mass Transfer and Useful Capacity. The term useful capacity, also referred to earlier as breakthrough capacity, differs from the equihbrium capacity shown on Figures 9a and 9b. The useful capacity is a measure of the total moisture taken up by a packed bed of adsorbent at the point where moisture begins to appear in the effluent. Thus the drying process cycle must be stopped before the adsorbent is fully saturated. The portion of the bed that is not saturated to an equihbrium level is called the mass-transfer 2one. 

Carefully fractionated through a gauze-packed column. Redistil and collect in weighed glass vials and seal. Keep away from moisture. It undergoes alkyl exchange with alcohols and forms azeotropes, e.g. with MeOH the azeotrope consists of 70% (MeO)3B and 30% MeOH with b 52-54"/atm, d 0.87. [J Chem Soc 2288 7952 Chem Ind (London) 53 7952 J Am Chem Soc 75 213 7955.] Also dried with Na, then distilled. 

Strength increase (because the cellulose fibrils pack more closely). To prevent movement, wood should be dried to the value which is in equilibrium with the humidity where it will be used. In a centrally heated house (20°C, 65% humidity), for example, the equilibrium moisture content is 12%. Wood shows ordinary thermal expansion, of... 

---