- Background and Overview
Modified melamine formaldehyde resin, also known as melamine formaldehyde resin or melamine resin, is an important triazine ring compound. It is a product synthesized by the addition reaction of melamine and formaldehyde, and then dehydrated and condensed. Melamine resin has excellent water resistance, aging resistance, flame resistance, heat resistance, chemical corrosion resistance and insulation properties. It can be used in the manufacture of molded plastics (daily-use tableware and electrical appliances), artificial boards (plywood, laminated wood flooring and laminated plastic boards) and foam. Besides, melamine resin is also widely used as coating, wood adhesive, paint cross-linking agent, fiber textile finishing agent, paper wet strength agent and cement water reducing agent, etc.
- II. Application
- Application in leather industry
In the leather industry, melamine resin is commonly used as pre-tanning, retanning and filling resin, among which the trihydroxymethyl melamine resin is the most widely used amino resin. Amino resins have a tanning mechanism similar to that of aldehyde tanning: the prepolymer penetrates into the leather, and as the pH value decreases, the prepolymer automatically condenses into molecules of a certain size within the leather. Then, the active -NHCH 2 OH in the molecule condenses with the amino group on the collagen peptide chain, forming a covalent cross-linked system for tanning purposes. At the same time, the amino resin has a filling effect. Through testing means, it is found that this resin has both tanning and filling properties, and can be filled between the collagen fibers of leather in large quantities to achieve the effect of making the leather body plump.
Melamine resin tanning agent is used in the retanning of chrome tanned light leather, which can make the finished leather with detailed grain, full body and bone, obvious thickening, good whitening effect and good light resistance. And it has good compatibility with other tanning agents. If used in combination with vegetable tanning agent, it can promote the penetration and absorption of vegetable tanning agent and increase the wear resistance and weather resistance of leather. If it is used in the retanning of suede, the effect of pile is good.
- Application in paper industry
Used as a wet enhancer, anti-water agent principle and performance characteristics because melamine formaldehyde resin contains hydroxymethyl, can form an etherification structure between fiber bundles. This cross-linking between different molecules and produce water resistance, so that the paper sheet to obtain the effect of moisture strength, so in the paper industry is mainly used as a wet reinforcing agent, anti-water agent. Used in the papermaking industry is mainly three hydroxymethyl melamine, but because of its stability, water solubility and free formaldehyde content are not ideal and have a negative impact on the whiteness and durability of the paper, it is now widely used is a modified resin.
- Used as ceramic and cement dispersant
Melamine formaldehyde resin sulfonate is a good anionic surfactant, with surface activity and other valuable properties, commonly used at home and abroad as ceramics, cement, concrete in the efficient dispersant or water reducing agent. Its mechanism of action is mainly: this type of water reducing agent has adsorption and dispersion and lubrication, so the use of less water can improve the compatibility of concrete, so as to achieve the purpose of water reduction. As the water mixing ratio decreases, the pores in the concrete are reduced, making the cement more dense and increasing the strength, which can also reduce the amount of cement. Due to the infiltration of water reducing agent, cement hydration products grow slowly, sulfonated concrete mesh structure is more dense, which is conducive to the increase in long-term strength of concrete.
- Used as wood adhesive
In the wood industry, melamine formaldehyde resin is mainly used as an adhesive. Since it has a large chemical activity, in penetrating into the wood products, cross-linking hardening speed is faster. Under the condition that no other hardener is needed, it can be thermally hardened or room temperature hardened, thus producing a bonding effect. Because of its thermal stability, water resistance, and chemical resistance, it is widely used in artificial board, wood, construction, paper packaging, and other fields. The focus in this field is mainly on how to overcome the cracking phenomenon and get a moderately flexible melamine formaldehyde resin, and the current solution is such as adding polyvinyl alcohol. Because it can react with formaldehyde to produce polyvinyl alcohol methanol, uniformly distributed in the resin to block the MF resin molecules in the triazole molecules close to play a toughening effect, to prevent cracking.
- Used as fabric printing and dyeing finishing agent
In the textile industry, melamine formaldehyde resin and derivatives are important raw materials for the preparation of fabric printing and dyeing finishing agents. Its mechanism of action is mainly as a surface modifier and coupling agent for fabrics, thus improving the performance of cotton fabrics in terms of shrinkage prevention, wrinkle prevention and washing resistance. However, due to poor storage stability, the effect of the fabric feel rough and easy to absorb chlorine yellowing and other shortcomings, the modification of its research is also increasing. The current use of methanol etherification of melamine resin, adding cyclic vinylidene urea, borax and other formaldehyde modifiers to get ultra-low aldehyde high stability of modified melamine formaldehyde resin finishing agent. The modified resin is used for bleached poplin to prevent shrinkage and wrinkle finishing, yellowing and chlorine damage can be improved, washing resistance is also better. The modified resin was used for anti-shrink and anti-wrinkle finishing of bleached poplin.
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