REPORT: 1T.R.

D E P A M E O FC H E M A L ENGINE ERING RT NT ICKM Y 401 CHE M CA L ENGINEERING DESIGN I

EGE UNIVERSITY

PROJECT: FORMALIND N PRO U CTIO

1.0SUM M ARY

INTRODUCTIONi 1

2.0 RESULTS3 Submitted to: 2.1 PHY SICA L PROPERTIES Prof. Dr. H. Ferhan ATALAY 5 Prof. Dr. Firuz BALKA Assist. Dr. Zehra ZELK 2.2 CHEMICAL REACTIONS 7 2.1.1 DECOMPOSITION BORNOV A/IZMIR 7 2.1.2 POLYMERIZATION 7 Prepared by: 05057361 Gnter KULEOLU 05057274 Duygu BAYRAKTAR 05057288 Sinem ARMA Y 05057330 Aya ATA

08.10.2008

7 2.1.4 AD DITION REACTIONS 8 2.1.5 CONDENSATION REACTIONS ONTENTS 8 2.1.6 RESIN FORMATION 9

C

2.3 U S A G E A ARE9

2.4 S T O G E A N DTRANSPORTATION RA11

2.5 TOXICOLOGY, OPERATIONAL HEALTH A N DPROCE S S SAFETY13 2.5.1 A CU T ETOXICITY 14 2.5.2 C ANCE R EPIDEMIOLOGY16

2.5.3 ANIMAL C ANCE R STUDIES 19 2.5.4 GENOTOXICITY 19 2.5.5 FIR E AN D E XPL O S N HAZARD IO 20 2.5.6 REACTIVITY 20 2.5.7 E M E G E N AN D FIRST AID PROCEDURES R CY 20 2.5.8 sp?ll, leak and d?sposal procedures 21 2.5.9 mon?tor?ng and measur?ng procedures 21 2.5.10 protect?ve equ?pment and cloth?ng 22 2.5.1 1 eng?neer?ng and controls

2.5.12 med?cal surve?ll ance 23 2.5.13 env?ronmental ?ssues 24 SUMMARY

2.6 the aqueous form (37 Formalin is econom?c aspectswt%) of formaldeyhde produced mostly from 25 methanol by an oxidation process. Because formaldehyde is highly water soluble, it is usuallymarketed as a liquid solution, typically at 37 weight percent formaldehyde solution, combined 2.7 d?sposal with water and up to 16 percent methanol. Recently, the production volume of formaldehyde 31 has grown rapidly with increasing demand in manufacturing sector for resins including phnolic, urea, melamin, acetal many additives. Other additional application areas of formaldehyde DISCU S S N & CONCLUSIONS include IO surface coating, leather tanning, bindery applications, laminates, insulation materials, etc. Also, formaldehyde is a preservative disinfection of bacteria. 32

3.0

4.0 R process and excess methanol EFERENCES excess air process and combined cataylst process. The 5.0

Formalin is mainly manufactured by methanol oxidation of which processes are

basic difference between them is the catalyst applied. The methanol excess process, called the 37 silver process, employs silver as the catalyst while the air excess process (molybdenum process) uses metallic oxides of iron and molybdenum. In considering higher investment cost apPend?CES and more complicated operation than the silver process, it is recommended to use the silver process. 38-45

Uses of formalin can be summarized as follows: Phenol resin and adhesives, urea and melamine adhesives Urea resin, melamine resin, hexamethy lenetetramine Pentaerythritol, paraformaldehyde Medicines and agricultural chemicals Polyacetal resin Hemiformal Moreover, use of formaldeyhde derivatives and formalin are explained comprehensively in Results part. Manufacturing processes of formalin are studied and the flow sheets of the processes are given in the Appendix part. Also, there are known effects of formaldehyde and its derivatives, therefore the needed information about its toxicology, exposure even occupatioanl health and environmental issues are given in the Results section.

1.0 INTRODUCTIONSince Blums proposal of formalin as a useful general biological fixative in 1893 it has become an unsurpassed standard. For 119 years zoologists, botanists, histologists, and pathologists have used formalin to preserve their materials for a detailed anatomical, histological or cytological study. To pathologists it represents until now the only admissible standard, in spite of the denounced toxicity of the product. Formalin is an aqueous solution of formaldehyde. The typical concentration is 37 - 40 %. That is, it is expected that a commercial formalin has 370 - 400 g of formaldehyde in each 1000 g of commercial solution. The intended dilution is w/w, not vol/vol. Formaldehyde is a nearly colorless gas with a pungent, irritating odor even at very low concentrations (below 1 ppm). Its vapors are flammable and explosive. Because the pure gas tends to polymerize, it is commonly used and stored in solution. Formalin, the aqueous solution of formaldehyde (30% to 50% formaldehyde), typically contains up to 15% methanol as a stabilizer. As formaldehyde is self-reactive, and continues to oxidize in aqueous solution producing formic acid, and in older solutions may even form a precipitate of paraformaldehyde (a solid polymerized formaldehyde). Formalin solutions thus really contain formaldehyde, paraformaldehyde, formic acid, and methanol. Formaldehyde is used in the manufacture of plastics; urea-formaldehyde foam insulation; and resins used to make construction materials (e.g., plywood), paper, carpets, textiles, paint, and furniture. The first industrial process for production of formalin, an aqueous solution of formaldehyde, was based on oxidative dehydrogenation of methanol over a copper catalyst. Improvements in catalyst technology resulted in substitution of the copper catalyst for an unsupported silver catalyst, which is the formula still used today. In the 1950s a competing process for production of formaldehyde was developed. This process was based on selective (partial) oxidation of methanol over an Fe-Mo (molybdenum and iron) oxide catalyst. The two processes, (Oxidation-dehydrogenation using a silver catalyst involving either the complete or incomplete conversion of methanol; and the direct oxidation of methanol to formaldehyde using metal oxide catalysts (Formox process)), referred to as silver and oxide processes respectively, are used today for the production of formalin on the industrial scale. Each process accounts for about 50% of the total production of formalin, which today amounts to about 20Mton per annum, expressed as 37 wt% HCHO in water.

In the silver process, vapourised methanol with air and steam is passed over a thin bed of silver-crystal catalyst at about 650 C. Formaldehyde is formed by the dehydrogenation of methanol. The heat required for the endothermic reaction is obtained by burning hydrogen contained in the off-gas produced from the dehydrogenation reaction. The other process, oxide process, involves the oxidation of methanol over a catalyst of Fe-Mo oxide. A mixture of air and methanol is vapourised and passed into catalyst-packed reactor tubes. The reaction which takes place at 350 C is highly exothermic and generates heat to provide steam for turbines and process heating. Yields from both processes are around 90% to 92% but the oxide process has a lower reaction temperature and the metal catalyst is cheaper than silver. However, the silver process is still the most prevalent. A wide range of alternative feedstocks have been considered but not found to be economic. For example, a tiny amount is produced from the non-catalytic oxidation of propane-butane mixtures. Formaldehyde can be produced from methane but a mixture of products needs to be separated. It is also a byproduct of the oxidation of naphtha to acetic acid. Formaldehyde can cause irritation of the eyes, nose, and throat, even at low levels for short periods. Longer exposure or higher doses can cause coughing or choking. Severe exposure can cause death from throat swelling or from chemical burns to the lungs. Direct contact with the skin, eyes, or gastrointestinal tract can cause serious burns. Drinking as little as 30 mL (about 2 tablespoons) of formalin can cause death. Formate, a formaldehyde metabolite, can cause death or serious systemic effects. Generally, more serious the exposure to formaldehyde is the more severe are the symptoms. Previously sensitized persons may develop a skin rash or breathing problems from very small exposures. Formaldehyde has low cost, high purity, and variety of chemical reactions, so it has become one of the worlds most important industrial and reasearch chemicals. More than 50 branches of industry now use formaldehyde, mainly in the form of aqueous solutions and formaldehyde-containing resins. Worldwide production of formaldehyde is 3 10 t / a .6

o

o

2.0 RESULTSFormaline process description information and other related information found in literature during feasibility study is composed in a logical order. Firstly process description is given as a result: The direct synthesis of formaldehyde from hydrocarbons has not yet resulted in cost reductions and because of the reactivity of formaldehyde, its handling and separation, as well as its direct preparation from hydrocarbons, are difficult. These factors, in the past, have exerted considerable influence on the pattern of formaldehyde growth. Currently, the only and competing production technologies for formaldehyde of commercial significance are based on the partial oxidation and dehydrogenation of methanol using a silver catalyst, or partial oxidation of methanol using a metal oxide-based catalyst since nearly all of the world's formaldehyde is made from methanol. In the silver catalyst route, which is also known as Methanol Excess Process, vaporized methanol with air and steam is passed over a thin bed of silvercrystal catalyst at about 650C. Formaldehyde is formed by the dehydrogenation of methanol. The heat required for the endothermic reaction is obtained by burning hydrogen contained in the off-gas produced from the dehydrogenation reaction. The other route, which is also known as Air Excess Process, involves the oxidation of methanol over a catalyst of molybdenum and iron oxide (Formox Process - developed and licensed by Reichhold Chemicals). A mixture of air and methanol is vaporized and passed into catalyst-packed reactor tubes. The reaction which takes place at 350C is highly exothermic and generates heat to provide steam for turbines and process heating. A high pressure version of the Formox Process called as Perstorp Process also exists, which can be retrofitted to existing plants to boost capacity. The high conversion rate of the process eliminates the need for methanol recovery via distillation, and it can produce formaldehyde at concentrations up to 57%.SILVER CATALYST PROCESS:

The silver catalyst process employs two main reactions,

which are given below, to convert methanol to formaldehyde: Dehydrogenation and Partial Oxidation. CH 3OH HCHO + H 2 CH 3OH + 1 O2 2 HCHO + H 2O

The equilibrium conversion in the dehydrogenation reaction is highly temperature dependent. The amount of process air controls the temperature by supplying oxygen to the exothermic reactions, including oxidation of hydrogen. The addition of inert materials such as water or nitrogen can also aid conversion by permitting the use of higher methanol concentrations relative to oxygen without entering the explosive region. These techniques permit variations in the process: Incomplete conversion plus separation and recycle of unreacted methanol, Complete conversion. The usual commercial form of the silver catalyst process involves incomplete conversion of methanol at lower temperatures, which minimizes byproducts, followed by distillation to remove and recycle the methanol. This allows the fine-tuning of the amount of methanol in the final product. Formaldehyde product may be produced at concentrations of up to 52- 55% by adjusting the amount of water added in formaldehyde absorption. Methanol concentrations can be adjusted as required (normally less than 1%) by distillation. In some cases, an ion exchange unit is needed to reduce the formic acid concentrations, but most commercial processes claim a figure of 0.06% without ion exchange. The methanol conversion per pass is typically 75- 85%, and overall process yield of formaldehyde from methanol is 90- 92 mol percent. Impurities, particularly iron, determine the catalyst life. The catalyst bed has a tendency to become matted under conditions of high temperature and throughput. Catalyst life is typically one year and it may be electrolytically regenerated. Although steam is generated internally, with most designs there is a net steam import requirement. At a temperature of around 700C, methanol conversion is sufficiently high to dispense with the final distillation column. A complete conversion process plant is similar to that described for incomplete conversion, described above, in most other respects.METAL OXIDE CATALYST PROCESS:

The basis of the metal oxide catalyst process is the

vapor-phase oxidation of methanol with excess oxygen (from air) at temperatures of 250400C.

Metal oxides in the catalyst are typically molybdenum and iron at a molar ratio of 1.5 to 2.0 (Mo:Fe). Small amounts of oxides of vanadium, cobalt, phosphorus, chromium and copper may also be included. Further reactions can occur to some extent, depending on temperature. These include the continued oxidation of formaldehyde to formic acid and carbon monoxide, and dehydration of methanol to dimethyl ether. A significant variation on this process is the absorption of the formaldehyde into a urea solution to make urea-formaldehyde precondensate. This can be used for the production of urea-formaldehyde resins, the largest single use of formaldehyde. Recycle of inerts permits the use of relatively high methanol concentrations without creating an explosive mixture. Oxygen concentration is kept to approximately 10%, whereas methanol is around 6- 9%, both on a molar basis. The Fe/Mo oxide catalyst is relatively insensitive to impurities such as iron carbonyls in the methanol feedstock. In a typical design, the catalyst is supplied as rings, and a very constant temperature profile is maintained by the use of a number of layers with different catalytic activities. A typical catalyst life is 18 months. Export steam from the process is around 0.5 pound per pound of product. Licensors claim methanol conversion per pass of 92- 94%. Therefore, no distillation column is required to recover and recycle methanol in the product stream. Maximum methanol content ranges from between 0.5 and 1.0 percent for 37 weight percent product to 1.5 percent for 50 weight percent product. The formaldehyde solution typically contains 0.02- 0.04 percent formic acid. If required, the formic acid concentration can be further reduced in an ion exchangers.2.1 PHYSICAL PROPERTIES

Formaldehyde, CH2O, formula weight 30.03 is the first member of the series of aliphatic aldehydes, is a colorless gas at ambient temperature that has a pungent, suffocating odor and an irritant action on the eyes and skin.

Formaldehyde gas is flammable, its ignition temperature is 430 C; mixtures with air are explosive. At ca. 20 C the lower and upper explosive limits of formaldehyde are ca. 7 and 72vol% (87 and 910 g/m ), respectively. Flammability is particularly high at a formaldehyde concentration of 65-70 vol %. At a low temperature, liquid formaldehyde is miscible in all proportions with nonpolar solvents such as toluene, ether, chloroform, or ethyl acetate. Polar solvents, such as alcohols, amines or acids, either catalyze the polymerization of formaldehyde or react with it to form methylol compounds or methylene derivatives. Since pure formaldehyde is a gas at ordinary temperatures and cannot be readily isolated or handled in this state, it is marketed chiefly in the form of its aqueous solutions. Monomeric physically dissolved formaldehyde is only present in low concentrations of up to 0.1 wt%. At ordinary temperatures, formaldehyde gas is readily soluble in water, alcohols and other polar solvents. Dissolution of formaldehyde in water is exothermic, the heat of solution (62 kJ/mol) being virtually independent of the solution concentration. Clear, colorless solutions of formaldehyde in water can exist at a formaldehyde concentration up to % wt 95, but the temperature must be raised to 120 C to obtain the highest concentrations. Concentrated aqueous solutions containing more than 30 wt% formaldehyde becomes cloudy on storage at room temperature, because larger poly glycols are formed which then precipitate out. The partial pressure of formaldehyde in equilibrium with the solution is low, due to solvation, and is a function of methylene glycol concentration rather than the total formaldehyde content. Formaldehyde is apparently not appreciable associated in the gaseous state, and its partial pressure may be regarded as the decomposition pressure of the dissolved hydrate. These factors explain the fact that formaldehyde solutions may be concentrated by vacuum evaporation at low temperatures, whereas pressure distillation at high temperatures makes its possible to obtain concentrated distillates from dilute solutions. On distillation at ordinary pressures without rectification, the still residue is always somewhat more concentrated than the distillate solution. Fractional condensation of the vapors of boiling solutions results in increasing ratio of formaldehyde to water in uncondensed vapors since water is the least volatile constituent of the mixed vapor. For more information on physical properties of formalin, see the MSDS given in Appendix.3

2.2 CHEMICAL REACTIONS

Formaldehyde is one of the most reactive organic compounds known and, thus, differs greatly from its higher homologues and aliphatic ketones. Formaldehyde will combine chemically with practically every type of organic chemical with the exception of paraffin. It can be employed as in the form of monomer, solution or polymer with essentially equivalent result. In general, the form used is of importance chiefly in its effect on the rate of reaction. Monomeric and polymeric forms are of special value where the presence of water is undesirable. Solutions and polymers are less reactive than the monomer, since they represent lower energy potentials in which the aldehyde has already reacted with itself or water. The most important reactions are treated as below:2.2.1 DECOMPOSITION

At 150 C, formaldehyde undergoes

heterogeneous decomposition to

form

mainly methanol and CO2. Above 350C, however, it tends to decompose into CO and H2. Metals such as platinum, copper, chromium, and aluminum catalyze the formation of methanol, methyl formate, formic acid, CO 2, and methane.2.2.2 POLYMERIZATION

Anhydrous

monomeric

formaldehyde slowly

cannot at

be

handled

commercially. 100 C,

Gaseous formaldehyde

polymerizes

temperatures

below

polymerization being accelerated by traces of polar impurities such as acids, alkalis, or water. Thus, in the presence of steam and traces of other polar compounds, the gas is stable at ca. 20 C only at a pressure of 0.25-0.4 kPa, or at a concentration of up to ca. 0.4 vol% at ca. 20 C and atmospheric pressure. Monomeric formaldehyde forms a hydrate with water; this hydrate reacts with further formaldehyde to form polyoxymethylenes. Methanol or other stabilizers, such as guanamines or melamines, are generally added to commercial aqueous formaldehyde solutions (37-55 wt%) to inhibit polymerization.2.2.3 REDUCTION AND OXIDATION

Formaldehyde is readily reduced to methanol with hydrogen over a nickel catalyst. For example, formaldehyde is oxidized by nitric acid, potassium permanganate, potassium dichromate, or oxygen to give formic acid or CO, and water, In the presence of strong alkalis or when heated in the presence of acids, formaldehyde undergoes a Cannizzaro reaction with formation of methanol and formic acid. In the presence

of aluminum or magnesium methylate, paraformaldehyde reacts to form methyl formate (Tishchenko reaction).2.2.4 ADDITION REACTIONS

The formation of sparingly water-soluble sodium formaldehyde bisul-fite is an important addition reaction of formaldehyde. Hydrocyanic acid reacts with formaldehyde to give glycolonitrile. Formaldehyde undergoes an acid-catalyzed Pnns reaction in which it forms a-hydroxy-methylated adducts with olefms .Acetylene undergoes a Reppe addition reaction with formaldehyde to hydroxide form 2-butyne-l,4-diol. Strong alkalis or calcium convert formaldehyde to a mixture of sugars, in particular hexoses, by a

multiple aldol condensation which probably involves a glycolaldehyde intermediate. Mixed aldols are formed with other aldehydes; the product depends on the reaction conditions. Acetaldehyde, for example, reacts with formaldehyde to give pentaerythritol, C(CH,OH)4 .2.2.5 CONDENSATION REACTIONS

Important condensation reactions are the reaction of formaldehyde with amino groups to give Schiff s bases, as well as the Mannich reaction. Amines react with formaldehyde and hydrogen to give methyl-amines. Formaldehyde reacts give hexamethylenetetramine, and with with ammonia to

ammonium chloride to give monomethylamine, dime- thylamine, or trimethylamine and formic acid, depending on the reaction conditions. Reaction of formaldehyde with diketones and ammonia yields imidazoles. Formaldehyde reacts with many compounds to produce methylol (-CH2OH) derivatives. It reacts with phenol to give methylolphenol, with urea to give mono-, di-, and trimethylolurea, Aromatic with formaldehyde presence benzyl chloride. Formaldehyde reacts with hydroxylamine, hydrazines, or semicarbazide to produce formaldehyde oxime (which is spontaneously converted to triformoxime), the corresponding hydrazones, and semicarbazone, respectively. Double bonds are also produced when formaldehyde is reacted with malonates or with primary aldehydes or ketones possessing a CH2 group adjacent to carbonyl group. with melamine such as the to give benzene, methylolmelamines, aniline, and and with organometallic compounds to give metal-substituted methylol compounds. compounds to toluidine combine In the produce corresponding diphenyl-methanes.

of hydrochloric acid and formaldehyde, benzene is chloromethylated to form

2.2.6 RESIN FORMATION

Formaldehyde condenses with urea, melamine, urethanes, cyanamide, aromatic sulfonamides and amines and phenols to give a wide range of resins.2.3 USAGE AREA

Formalin is an aqueous solution of formaldehyde. Formaldehyde has been used for many years in consumer goods to deter spoilage caused by microbial contamiantion. It has been used as a preservative in household cleaning agents, dishwashing liquids, fabric softeners, shoe-care agents, car shampoos and waxes, and carpet cleaning agents. Generally the formaldehyde content in these products is less than 1%. Formaldehyde is commercially offered as a 37 wt% to 50 wt% aqueous solution, with 37 wt% (known as formalin or formol) being the most widely used grade which may also contain 0-15 wt% methanol and a polymerisation inhibitor. As formaldehyde is self-reactive, and continues to oxidize in aqueous solution producing formic acid, and in older solutions may even form a precipitate of paraformaldehyde (a solid polymerized formaldehyde). Formalin solutions thus really contain formaldehyde, paraformaldehyde, formic acid, and methanol. 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. Products manufactured using organic compounds, where formaldehyde is used as a chemical intermediate in their production, include: plywood adhesives, abrasive materials, insulation, foundry binders, and brake linings made from phenolic resins, surface coatings, molding compounds, laminates and wood adhesives made from melamine resins; phenolic thermosetting, resins curing agents and explosives made from hexamethylenetetramine; urethanes, lubricants, alkyd resins and multifunctional acrylates made from trimethylolpropane; plumbing components from polyacetal resins; and controlled-release fertilizers made from urea formaldehyde concentrates. Polyacetal plastics produced by polymerization of formaldehyde are incorporated into automobiles to reduce weight and fuel consumption. They are also used in the manufacture of functional components of audio and video electronics equipment. Formaldehyde solutions have also been used for disinfecting dwellings, ships, storage houses, utensils, and clothing. Solutions containing 28% formaldehyde have been used as

germicides to disinfect inanimate objects. Formaldehyde is used as a tissue preservative and disinfectant in embalming fluids. In agricultural industry, formaldehyde has been used as a fumigant, as a preventative for mildew and spelt in wheat, and for rot in oats. It has been used as a preplanting soil sterilant in mushroom houses. Formaldehyde has been used as a germicide and a fungicide for plants and vegetables; as an insecticide for destroying flies and other insects; and in the manufacture of slow-release fertilizers. Approximately 80% of the slow-release fertilizer market is based on urea-formaldehyde-containing products. Formaldehyde continues to be used in the manufacture of glass mirrors, explosives, artificial silk and dyes; for waterproofing fabrics; for preserving and coagulating rubber latex; and for tanning and preserving animal hides. In photography industry, formaldehyde has been used for hardening gelatin plates and papers, toning gelatin-chloride papers, and for chrome printing and developing. Formaldehyde is used as an antimicrobial agent in many cosmetic products, including soaps, shampoos, hair preparations, deodorants, lotions, make-up, mouthwashes, and nail products. Formaldehyde is incompatible with ammonia; alkalies; tannin; iron preparations; and salts of copper, iron, silver, potassium permanganate, iodine, and peroxide. When it is used as a preservative in shampoos, formaldehyde may interact unfavorably with both fragrance components and color additives. Some cosmetics have reportedly contained 0.6% formaldehyde, while concentrations as high as 4.5% have been detected in nail hardeners. Formaldehyde concentrations in dry-skin lotions, creme rinses, and bubble bath oils have reportedly ranged from 0.4 to 0.5%. Formaldehyde has also been found in sun-tan lotion and hand cream, bath products, mascara and eye make-up, cuticle softeners, nail creams, vaginal deodorants, and shaving creams. Trace amounts of formaldehyde found in cosmetic products could also result from its use as a disinfectant of the manufacturing equipment. Compared to its use in product manufacturing, the use of formaldehyde in the medical fields is relatively small. Consumption in this area averages approximately 1.5% of the total production volume. Some of the earlier, minor, medicinal applications for formaldehyde included its use during vasectomies, as a foot antiperspirant or as a preservative in such products, as a treatment for athletes foot, and as a sterilant for echinococcus cysts prior to their surgical removal. In veterinary medicine, formaldehyde has been used therapeutically as an antiseptic and as a fumigant. It has also been used to treat tympany, diarrhea, mastitis, pneumonia, and internal bleeding in animals. In animal nutrition, formaldehyde is used to

protect dietary protein in ruminants. It is used as a food additive to improve the handling characteristics of animal fat and oilseed cattle food mixtures. Other industries using formaldehyde in their processes include the sugar industry where formaldehyde is used as an infection inhibitor in producing juices; the rubber industry where it is used as a biocide for latex, an adhesive additive, and an anti-oxidizer additive for synthetic rubber; and the food industry where it is used for preserving dried foods, disinfecting containers, preserving fish and certain oils and fats, and modifying starch for cold swelling. It has been use as a bacteriostatic agent in some foods, such as cheese. In the petroleum industry, formaldehyde is used as a biocide in oil well-drilling fluids and as an auxiliary agent in refining. Formaldehyde has been used as an anti- corrosive agent for metals. In the plastics industry, for the preparations of phenol, urea, and melamine resins, where the presence of water could interfere with the production process, paraformaldehyde may be used in place of aqueous formaldehyde solutions. In addition to its use in selected pesticide applications, paraformaldehyde has also been used in making varnish resins, thermosets, and foundry resins, the synthesis of chemical and pharmaceutical products, the preparation of disinfectants and deodorants, and the production of textile products. Formaldehyde was used in the textile industry as early as the 1950s when formaldehydebased resins were initially used to produce crease-resistant fabrics. Postproduction analysis indicated that these early resins contained a substantial amount of extractable formaldehyde (more than 0.4% by weight of the fabric. With the introduction of new resins and other process modifications in the 1970s, the level of extractable formaldehyde in crease-resistant fabrics gradually decreased to 0.010.02%.2.4 STOR AGE AND TRANSPORTATION

With a decrease in temperature and/or an increase in concentration, aqueous formaldehyde solutions tend to precipitate paraformaldehyde. On the other hand, as the temperature increases, so does the tendency to form formic acid. Therefore, an appropriate storage temperature must be maintained.

Table 2.1: Storage temperatures for commercial formaldehyde solutions.

Formaldehyde content, wt% 30 37 37 37 50 50

Methanol content, wt% 1