Formaldehyde-tanned leather

Oil-tanned chamois leather Alum-tawed skins Formaldehyde-tanned leather Aluminium-tanned skins Vegetable-tanned leather (hydrolysable) Vegetable-tanned leather (condensed) Chrome-tanned leather... 

Formaldehyde has been rated as a possible carcinogen by the United States Occupational Safety and Health Act (OSHA) rules and should be handled with due caution. It is also a strong lacrymator and choking respiratory irritant. It irritates the skin, eyes, and mucous membranes [76]. Since it is used for tanning leather, it is obvious that fonnaldehyde has a high potential for reactions with proteins. Formaldehyde gas is flammable and most formalin solutions contain significant amounts of methanol, which is also volatile, toxic, and flammable. 

Melamine formaldehyde resin, 10% pet (re-tanning, leather finish)... 

Thus, by preparing and assembling the shoe parts, an occupational exposure is given to a broad spectrum of allergens. Additionally, an exposure to allergens from freshly tanned leather (formaldehyde, glutaral-dehyde, azo dyes, chemicals from leather finishes) is possible. 

Colophony, 20% petrolatum. Adhesives Formaldehyde, 1% aqua. Preservative in natural rubber glues tanned leather... 

Miscellaneous. In ore flotation, sodium sulfite functions as a selective depressant. In textile processing, sodium sulfite is used as a bleach for wood (qv) and polyamide fibers and as an antichlor after the use of chlorine bleach. Synthetic appHcations of sodium sulfite include production of sodium thiosulfite by addition of sulfur and the introduction of sulfonate groups into dyestuffs and other organic products. Sodium sulfite is useful as a scavenger for formaldehyde in aminoplast—wood compositions, and as a buffer in chrome tanning of leather. 

Tanak MRX [Cytec]. TM for melamine-formaldehyde resin tanning agent used to make pure-white leather and for bleaching and filling chrome leather. 

Formic acid, like formaldehyde, has good disinfectant properties. It exists in honey preventing it from being spoilt easily. It is also used in textile dying and leather tanning. In addition, formic acid is a starting material in the production of fertilizers, rubbers and plastics. Plus the calcium salt of formic acid is a good softener when dissolved in water. 

Straight melamine-formaldehyde resins are used primarily in the preparation of molding compounds, laminates, and textile finishes. Nearly 90% of these molding powders are used to make dinnerware. Melamine dinnerware can be made very decorative for popularity. This resin has better physical properties than phenolics and it can be very easily colored, which phenolics cannot. Methylolmelamine also is used as a synthetic tanning agent for white leather. 

Today formaldehyde finds widespread use in the hardening of gelatin, preservation of food, disinfection, tanning of leather and, most important, in the production of resins by condensation with phenol (bakelite) and in the synthetic organic chemical industry. 

Formaldehyde was utilised to produce washable white leathers from the end of the nineteenth until the last third of the twentieth century when its use was phased out due to health and safety concerns. Other aldehydes have tanning properties but only glutaraldehyde has been employed successfully on a commercial scale. 

Methods aimed at the determination of tannin material content in the extract. The classical method of this type still used is the hide-power and derived methods. These methods were devised to determine which percentage of the extract would participate in leather tanning. The main drawback for their use for adhesives in their inability to detect and determine the approximate 3 to 6% of monoflavo-noids and biflavonoids, or phenolic nontannins, present in the extract which do not contribute to tanning capacity but which do definitely react with formaldehyde and contribute to adhesive preparation. 

Uses Forms synthetic resins with formaldehyde melamine resins organic synthesis fire-retardant intumescent paint ingred. mfg. of food-contact paper/paperboard leather tanning infood-pkg. adhesives... 

The collagen molecule can be cross-linked by a number of techniques to improve its structural integrity and biostability. An early example of this is the tanning of skin to make leather. The use of formaldehyde to preserve biological samples is another example. 

Although these tannins can be reacted with formaldehyde and other aldehydes, the rates of these interactions are low, and they are therefore not favoured for the preparation of resins. They have, however, been used successfully as partial substitutes (up to 50 per cent) of phenol in the manufacture of phenol-formaldehyde resins [9, 10]. Their chemical behaviour towards formaldehyde is analogous to that of simple phenols of low reactivity and their moderate use as phenol substitutes in the above-mentioned resins does not present difficulties. Their lack of macro-molecular stmcture, the low level of phenol substitution they allow, their low nucleophilicity, limited worldwide production and relatively high price, somewhat decrease their chemical and economical interest for resin production. Consequently, their main use is for leather tanning where their performance, especially in terms of clarity of colour and light resistance, is truly excellent. 

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