Melamine resin glues

Melamine resin glues are important in the woodworking field when weatherproof glue joints according to DIN 68705, category AW at relatively low press temperatures (under 100 °C) are required. With added extenders moisture-proof glue joints can be obtained that meet the requirements of the same DIN category IF, at press temperatures above 75 °C. 

Nitrogen component in urea-formaldehyde or melamine-resin glues in wood processing (less formaldehyde emissions) ... 

Glue resin mixes, for the application of melamine resins, 15 791 Glufosinate, 13 299, 325, 326, 357 crop resistance to, 13 359-360 metabolism of, 13 360 Glutamic acid... 

The consumption in the USA in 1996 was 3.83 10 t N, of which 83% was used in fertilizers. Half of the consumption in fertilizers was utilized in liquid fertilizers e.g. in urea-ammonium nitrate. solutions, the rest being used in solid fertilizers. 7% of urea was utilized for animal nutrition and 6% for urea-formaldehyde resins, glues and melamine. In the period between 1984 and 1996 there was a reduction in urea capacity in Western Europe of 39% to 2.5 10 t/a N (Table 2.2-7). 

Melamine (2,4,6,-triamino-1,3,5-triazine) is obtained by trimerization of cyanamide or commercially by thermal cyclocondensation of urea at 400°C with elimination of NH3 and CO2. Polycondensation of melamine with formaldehyde produces melamine resins that are used as plastics, glues and adhesives. Cyanuric acid 15 (2,4,6-trihydroxy-1,3,5-triazine) was obtained by Scheele (1776) from pyrolysis of uric acid and was the first 1,3,5-triazine derivative known. Cyanuric acid is synthesized by trimerization of isocyanic acid and is tautomeric with isocyanuric acid 16 ... 

Classical plywood UF-resin, also cold setting use is only possible with special hardeners and additives, e.g. melamine containing glue mixes for an enhanced water resistance. 

Correlations Between the Composition of Melamine Resins and Properties of Hardened Glue Lines and Wood-Based Panels... 

Glue Resin Mixes for the Application of Melamine Resins. Table 2... 

Melamine (2,4,6,-triamino-l,3,5-triazine) is obtained by trimerization of cyanamide or commercially by thermal cyclocondensation of urea at 400 °C with elimination of NH3 and CO2. Polycondensation of melamine with formaldehyde produces melamine resins that are used as plastics, glues, and adhesives. 

Over the years, various types of adhesives have been used in this application. Already in 1926, resins based on urea-formaldehyde were imported in the market by a company named LG. Farben (now BASF) and mark the beginning of structural adhesive technology in timber. Then, the resulting synthetic resin glues based on resorcinol and melamine have proven due to their excellent temperature and humidity resistance in work areas, where the bonded components are exposed to weathering or climatic conditions. The strength of the adhesive joint usually exceeds the inherent strength of the wood. 

By far the bulk of amino resins are used in the woodworking industry for the manufacture of chipboard, plywood and as general glues and adhesives. Melamine-formaldehyde is an important component of decorative laminates. The amount of amino resins used for moulding applications is only of the order of 5% of the total. 

Below 1. 00 Special glue resins for boards with a very low formaldehyde emission in most cases modified or fortified with melamine. 

Addition of melamine in various forms (pure melamine, MF/MUF-powder resin, melamine acetates) to an UF-resin during the application of the glue mix. In the case of the addition of pure melamine the UF-resin must have a rather high molar ratio, otherwise there is not enough formaldehyde available to react with the melamine in order to incorporate it into the resin. 

Uses of Formaldehyde. Formaldehyde is the simplest and most reactive aldehyde. Condensation polymerization of formaldehyde with phenol, urea, or melamine produces phenol-formaldehyde, urea formaldehyde, and melamine formaldehyde resins, respectively. These are important glues used in producing particle hoard and plywood. 

In hardwood plywood, the glue mix is typically formed by adding water and soft wheat flour at rather high proportions with a minor addition of filler, such as nut shell flour to the urea-formaldehyde resin. Urea-formaldehyde resins are usually shipped in 60 - 65 percent non-volatile solids form. Acid salts such as ammonium sulfate are added to increase the rate of cure of the urea-formaldehyde resin when under pressure and subsequently heated in hot presses. Some acid salts cure the urea-formaldehyde sufficiently well under ambient "cold" press conditions. It is evident this type of plywood would be oriented toward interior use such as furniture. If water-proof type bonds are required of hardwood plywood, then melamine-formaldehyde resins are used in similar mix form but with higher resin solids... 

Formaldehyde (CH20) is an important compound in the synthesis of various chemicals on an industrial scale. One of the first industrial applications was in the production of artificial Indigo. The variety of end products produced from formaldehyde include resins or glues (produced by the condensation of formaldehyde with urea, phenol, or melamine) as well as rubber, paper, fertilizers, explosives, engineering plastics, and specialty chemicals like acrolein, methacrylic acid, methyl methacrylate, etc. Because it is nearly impossible to handle in its pure gaseous form, formaldehyde is almost exclusively produced... 

Kauramin . [BA AG] Melamine-formaldehyde based glues fcv prod, of weather-resistant chipboard and plywood impregnating resins for decorative and overiay papers. 

---