Finishing chemicals formaldehyde

Fabric stored in warehouses can produce volatile emissions from process residues, especially printing, dyeing, or finishing chemicals that remain in the fabric. The most important of these is formaldehyde, but others, notably hydrocarbons (e.g., from softeners and wax water repellent finishes), can be present. 

Curing Catalysts for A Methylol Agents. Many acid-type catalysts have been used in finishing formulations to produce a durable press finish. Catalyst selection must take into consideration not only achievement of the desked chemical reaction, but also such secondary effects as influence on dyes, effluent standards, formaldehyde release, discoloration of fabric, chlorine retention, and formation of odors. In much of the industry, the chemical suppher specifies a catalyst for the agent so the exact content of the catalyst may not be known by the finisher. 

Researchers had noted the release of formaldehyde by chemically treated fabric under prolonged hot, humid conditions (85,86). The American Association of Textile Chemists and Colorists (AATCC) Test Method 112 (87), or the sealed-jar test, developed in the United States and used extensively for 25 years, measures the formaldehyde release as a vapor from fabric stored over water in a sealed jar for 20 hours at 49°C. The method can also be carried out for 4 hours at 65°C. Results from this test have been used to eliminate less stable finishes. 

The two amino resins in common use are urea formaldehyde and melamine formaldehyde, and most stoving finishes contain one or the other. They have many properties in common urea formaldehyde, however, while substantially cheaper, has poor exterior durability, whereas melamine formaldehyde imparts excellent exterior durability. As they are both water white they give white finishes of excellent colour, with the additional advantage of retaining their colour on over-stoving. Urea formaldehyde is commonly used in conjunction with a lesser quantity of an alkyd to give finishes with excellent resistance to water and mild chemicals, which are therefore well suited to use on domestic equipment, e.g. washing machines. 

I Btersen, H. A.. Cross-linking with formaldehyde-containing reactants, in Handhook of Fiber Sciente and Technology. Vol. 2 Chemical processing of fibers and fabrics.- Functional Finishes, Part A, Lewin, M. and Sello,... 

V,V-Dimethylol-4,5-dihydroxyethylene urea (DMDHEU) is the chemical basis of about 90 % of the easy-care and durable press finish products on the market. DMDHEU is synthesised from urea, glyoxal and formaldehyde as shown in Eig. 5.4. 

Levin M, Handbook of Fiber Science and Technology Vol. II. Chemical Processing of Fibers andFabrics. Functional Finishes Part A,Chnpters 1 (Cross-linking of cellulosics) and 2 (Cross-linking with formaldehyde-containing reactants). New York, Marcel Dekker, 1983. 

Although inorganic salts can provide excellent flame-retardant properties for cellulose, reasonable laundering durability must be incorporated into any finish destined for apparel use. The most successful durable flame retardants for cellulose are based on phosphorous- and nitrogen-containing chemical systems that can react with the fibre or form crosslinked structures on the fibre. The key ingredient of one of these finishes is tetrakis(hydroxymethyl)phosphonium chloride (THPC), made from phosphine, formaldehyde and hydrochloric acid (Fig. 8.11). THPC reacts with urea to form an insoluble structure on cellulose in a pad-dry-cure process (Fig. 8.12). 

The National Occupational Exposure Survey (NOES), conducted from 1981 to 1983, indicated that 1,329,332 workers employed in various professions were potentially exposed to formaldehyde in the United States (NIOSH 1995b). The NOES database does not contain information on the frequency, concentration, or duration of exposure the survey provides only estimates of workers potentially exposed to the chemical in the workplace. OSHA has estimated that in the late 1980s over 2 million workers in over 112,000 firms were exposed to formaldehyde about 45% of these workers are estimated to be in the garment industry. About 1.9 million were exposed to levels of formaldehyde between 0.1 ppm and 0.5 ppm (mainly in apparel, furniture, paper mills, and plastic molding) approximately 123,000 were exposed to levels of formaldehyde between 0.5 and 0.75 ppm (mainly in apparel, textile finishing, furniture, laboratories, and foundries) and about 84,000 were exposed to between 0.75 and 1 ppm (mainly in apparel, furniture, and foundries) (OSHA 1996). 

Formaldehyde is an important constituent of many textile finishes, especially finishes for cellulosic textiles. As the main chemical route to cross-linking cellulose, formaldehyde or a reactant made from formaldehyde is found in a variety of finishes, ranging from durable press agents to water repellents. 

---