Melamine-Formaldehyde Resins

Melamine-Formaldehyde Resins

 

synthetic products used in manufacturing plastics, carbamide glue, decorative laminated plastics, and varnishes. In terms of chemical composition, they are oligomers and are formed by polycondensation of melamine with formaldehyde.

Melamine-formaldehyde resins are synthesized in two stages with a 1:(2–12) molar ratio of melamine to formaldehyde. Various methylol derivatives of melamine are formed during the first stage at a temperature of 80°-90° C and pH 8.5; the second stage involves subsequent polycondensation of the products in an acid medium. For example, the reaction mixture must be cooled to 50°-60° C and a certain quantity of acid added to produce melamine-formaldehyde resins with the highest industrial value.

Melamine-formaldehyde resins are amorphous white products that are readily soluble in water but insoluble in organic solvents. The methylol groups in the resins undergo esterification with alcohols, primarily n-butanol and methanol, to impart to them hydrophobic properties, solubility in organic solvents (during the preparation of varnishes), and the ability to combine with plasticizers. Melamine-formaldehyde resins are cured at high temperatures, or at room temperature in the presence of slightly acidic catalysts.

REFERENCE

Tekhnologiia plasticheskikh mass. Edited by V. V. Korshak. Moscow, 1972.

G. M. TSEITLIN

References in periodicals archive ?
On the basis of resin type, global impregnating resins market is segmented as phenol-formaldehyde resins, urea-formaldehyde resins, and melamine-formaldehyde resins. On the basis of form, the market is further segmented into solventless, solvent-based.
(15.) Jonesa, FN, Chua, G, Samaraweera, U, "Recent Studies of Self-condensation and Co-condensation of Melamine-Formaldehyde Resins; Cure at Low Temperatures." Prog.
Pizzi, "Melamine-formaldehyde resins," in Handbook of Adhesive Technology, A.
Crosslinking is through the drying oil fatty esters and/or external crosslinkers such as melamine-formaldehyde resins. Epoxy ethers can be made from diepoxides and allyl alcohol with subsequent copolymerization with acrylic acid and styrene.
Reversibility of F-containing bonds is a specific feature of OF resins, compared to melamine-formaldehyde resins and ultimately also to phenol(resorcinol) formaldehyde resins [1].
Melamine-formaldehyde resins are already used heavily in laminate flooring, says Ulf Panzer of Agrolinz Melamine international GmbH.
40-EpEs-PET was modified with urea-formaldehyde and melamine-formaldehyde resins and epoxy ester-amino resin (40-EpEs-PET-AR) was synthesized.
However, at pH 8.5 co-condensed urea-melamines and hydroxymethylated ureas remain stable while hydroxymethylated melamine components probably condense further to form somewhat stable melamine-formaldehyde resins as shown by Pizzi (1994).
Additional measurements of the fractional conversions for other cure temperatures, should make it possible to establish a relationship between [T.sub.g] and fractional conversion for melamine-formaldehyde resins.
Work on fast-reacting natural and synthetic resins (all deficient in formaldehyde), mainly tannins (Pizzi and Tekely 1995), resorcinol-formaldehyde resins (Pizzi and Tekely 1996), and melamine-formaldehyde resins (Pizzi and Tekely 1996, Pizzi et al.
For comparison, the core material and reference sample, i.e., melamine-formaldehyde resin synthesized under the same procedure for the microcapsules, were evaluated as well.