Formaldehyde, 31 Table manufacture

Butynediol. Butynediol, 2-butyne-l,4-diol, [110-65-6] was first synthesized in 1906 by reaction of acetylene bis(magnesium bromide) with paraformaldehyde (43). It is available commercially as a crystalline soHd or a 35% aqueous solution manufactured by ethynylation of formaldehyde. Physical properties are Hsted in Table 2. 

Many members of this series are known based on nitroparaffin condensations with aldehydes of longer chain length than formaldehyde. However, only the five primary amino alcohols discussed in the following are manufactured on a commercially significant scale. N-Substituted derivatives of these compounds also have been prepared, but only 2-dimethylamino-2-methy1-1-propanol has been available in commercial quantities (Table 1). 

Various processes can be employed to manufacture urea—formaldehyde products. They are generally categorized into two types, ie, dilute solution processes and concentrated solution processes. Table 3 Hsts select U.S. manufacturers of UF reaction products and their products. 

Table 12.2 gives the uses for methanol. The percentage of methanol used in the manufacture of formaldehyde has been fluctuating. It was 42% in 1981. It has decreased in part because of recent toxicity scares of formaldehyde. The percentage of methanol used in acetic acid manufacture is up from 7% in 1981 because the carbonylation of methanol has become the preferred acetic acid manufacturing method. MTBE is the octane enhancer and is synthesized directly from isobutylene and methanol. It was... 

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. 

Recent work has concentrated on the use of ALCELL lignin as a substitute for phenol-formaldehyde resins in wood adhesives, particularly wafer-board. Some of the results obtained when a PF resin (Bakelite 9111) was replaced with different levels of hardwood ALCELL lignin in waferboard manufacture will be briefly discussed below. Table III shows the conditions used for waferboard manufacture. 

The Baker-Perkins double-screw mixer-extruders manufactured in the USA and Great Britain are employed for processing thermosetting materials, more specifically, urea-formaldehyde compounds. Basic specifications of these units are given in Table 5 26). 

Table 1.27 summarizes (he average eccmomic data concerning formaldehyde manufacturing processes using silver and iron molybdenum catalysts. They refer to the late technologies and a capacity of 67,500 t/year of 37 per cent weight formalin. 

Table 4-1 lists the facilities in each state that manufacture or process formaldehyde, the intended use, and the range of maximum amounts of formaldehyde that are stored on site. The data listed in Table 4-1 are derived from the Toxics Release Inventory (TRI96 1998). Only certain types of facilities were required to report. Therefore, this is not an exhaustive list. Table 4-2 shows capacity and production volumes for selected years between 1960 and 1978. 

Table 4-1. Facilities That Manufacture or Process Formaldehyde...

Formaldehyde is used as a chemical intermediate in the manufacture of a large variety of organic compounds, ranging from amino and phenolic resins to slow release fertilizers (Gerberich et al. 1980). Table 4-3 shows the distribution of formaldehyde use for select periods between 1963 and 1977. The demand for formaldehyde in North America was 11.6 billion pounds in 1995, a slight increase from the... 

According to the Toxics Release Inventory (TRI), in 1996, 21 million pounds (9.6 million kg) of formaldehyde were released to the environment from 674 domestic manufacturing and processing facilities (TRI96 1998). This number represents the sum of all releases of formaldehyde to air, water, soil, and underground injection wells. An additional 1.8 million pounds (0.8 million kg) were transferred to publicly owned treatment works (POTWs), and 1.3 million pounds (0.6 million kg) were transferred off-site (TRI96 1998). Table 5-1 lists amounts released from these facilities. The TRI data should be used with caution because only certain types of facilities are required to report (EPA 1995). This is not an exhaustive list. 

Table 5-1. Releases to the Environment from Facilities that Manufacture or Process Formaldehyde (continued)...

The effect of panel age on formaldehyde release was investigated in the first study summarized in Table I, and this variable was evidently very important with respect to the formaldehyde levels measured. As noted in the Remarks column in the table, formaldehyde levels ranged from 0.1 - 0.3 ppm for freshly manufactured specimens, while levels in the range of only 0.05 - 0.1 ppm were associated with matched specimens that had been aired out for 90 days at 23 C and 44% relative humidity. This aging effect is consistent with the theoretical considerations discussed earlier and with test results to be presented later in this report. 

Formaldehyde has been used for preservation for many years, as shown in Figure 22.9. Industrially, large quantities of formaldehyde are reacted with urea to manufacture a type of grease-resistant, hard plastic used to make buttons, appliance and automotive parts, and electrical outlets, as well as the glue that holds the layers of plywood together. Benzaldehyde and salicylaldehyde, shown in Table 22.7, are two components that give almonds their natural flavor. The aroma and flavor of cinnamon, a spice that comes from the bark of a tropical tree, are produced largely by cinnamaldehyde, also shown in Table 22.7. 

UF resins for particleboard with urea/formaldehyde molar ratios of 1 1.45, 1 1.32, and 1 1.25 have free formaldehyde contents of 0.8%, 0.3%, and less than 0.2%, respectively [15]. While the current tendency internationally is to use UF resins that have a urea/formaldehyde molar ratio lower than or much lower than 1 1.2, which release much less formaldehyde, these resins perform less well in the production of UF-bonded particleboard [15,17]. In particular, they do not allow as much flexibility in particleboard production as do resins with higher formaldehyde/urea molar ratios. This fact stresses the need for greater control and supervision of the production at particleboard plants where UF resins of low molar ratio are used. An example of the variation in properties between particleboard manufactured with different molar ratio resins is given in Table 1. 

The higher the molar ratio F/U, the higher is the content of free formaldehyde in the resin. Assuming stable conditions in the resins, which means that, e.g., post-added urea has had enough time to react with the resin, the content of free formaldehyde is very similar even for different manufacturing procedures. The content of formaldehyde in a straight UF resin is approximately 0.1% at F/U = 1.1 and 1% at F/U = 1.8 [19-21]. It also decreases with time due to aging reactions where this formaldehyde reacts further. Table 5 summarizes the various influences of the molar ratio F/U on various properties of wood-based panels. Table 6 summerizes the influence of the molar rations F/U and F/(NH2)2>... 

Amino resins are related polymers formed from formaldehyde and either urea or melamine. In addition to many of the uses listed earlier, they can be used to manufacture lightweight tableware, and counter and table surfaces. Being transparent they can be filled and colored using light pastel shades, whereas the phenohcs are already rather dark and, consequently, have a more restricted color range. 

According to Table 6, the best treatment is a straw particleboard made of 13% AESO resin content at 12 min pressing time. In Table 7 there is a comparison between our best treatment and EN standards for wood particleboards (EN 312-p2 Requirements for general purpose boards for use in dry conditions , EN 312-p4 Requirements for load-bearing boards for use in dry conditions ). This table shows that wheat straw particleboards with 13% AESO content manufactured at 12 min pressing time can totally compete with wood particleboard and can be a good biobased substitute for it, and also without any formaldehyde emission. 

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