Urea-Formaldehyde is commonly used as the adhesive to make ply wood for interior use. It is a non transparent, thermosetting polymer. Ply wood for exterior use is generally manufactured using Phenol-Formaldehyde resin, which is a more water resistant polymer. Phenol-Formaldehyde is not being discussed here.
I spent the day yesterday researching and trying to understand how Urea-Formaldehyde is produced.
The purpose of this post is to try to explain how I believe urea-formaldehyde is generally manufactured, in order to to establish what it is made from. I am craftsman, interested in the materials that I use. I am not a scientist. This means that I can only explain this subject on a simplistic level. It also means that I am interested to hear feedback from people with a greater scientific understanding of this subject. For example; Are there any sections of the manufacture process that I am misunderstanding?
If I’ve got this right though, It all starts with the fossil gas methane, and coal.
Urea-Formaldehyde resin is made with urea and formaldehyde. The reaction of these two compounds in such a way that they form resin that can become a stable polymer, involves 2 stages. Before this can happen though, the urea and the formaldehyde need to be produced.
Urea occurs in nature as the end product of protein metabolism by mammals, which excrete urea in urine. The manufacture of synthetic Urea begins with the mining and extraction of the fossil fuel Methane. Hydrogen is separated from the Methane through a process called ‘Steam Reforming’. This involves steam, high temperatures and high pressures and a nickle catalyst to separate the hydrogen from the carbon in the methane. A by product of this process is carbon dioxide, which is generally collected because it is required further down the line to make Urea. I wonder how effeciently the carbon dioxide is collected?
Having been extracted from the methane, the hydrogen is then combined with atmospheric nitrogen to make synthetic ammonia. This artificial nitrogen fixation process is called the Haber-Bosch process and once again uses a metal catalyst and high temperatures and pressures. Inteerstingly, Carl Bosch, one of the inventors of this process, was the nephew of Robert Bosch, who who pioneered the development of the spark plug and founded the multinational company Bosch.
The next step is called the Bosch–Meiser urea process and involves 2 stages. The first is carbamate formation: the fastreaction of liquid ammonia with gaseous carbon dioxide at high temperature and pressure to form ammonium carbamate. The second is urea conversion: the slower decomposition of ammonium carbamate into urea and water
Formaldehyde occurs naturaly throughout the universe. It is a simple chemical compound made of hydrogen, oxygen and carbon. All life forms – bacteria, plants, fish, animals and humans – naturally produce formaldehyde as part of cell metabolism. However for industrial purposes it is manufactured.
The creation of formaldehyde uses the Formox process which requires methanol and oxygen.
The methanol is made from hydrogen and carbon monoxide. The carbon monoxide is often obtained through the partial combustion of coal with air.
On an industrial scale, like in the manufacture of urea , the hydrogen required is predominantly produced from the natural gas methane by reforming the gas with steam, followed by the high pressure catalytic conversion of the synthesis gas to methanol. The result is a clear, liquid, organic chemical that is water soluble and readily biodegradable.
The liquid methanol is then subjected to the Formox Process; The catalytic oxidation of methanol at a temperature of 250-400oC. This produces the Formaldehyde required to combine with the Urea to make Urea-Formaldehyde Resin.
The actual reaction of urea and formaldehyde to form urea-formaldehyde resins gets pretty complicated. If I understand correctly it’s a 2 step process. Firstly, an alkaline methylation at a high formaldehyde to urea, consisting of the addition of up to 3 molecules of formaldehyde to one molecule of urea. This is then followed by an acidic condensation, meaning that water and an acid are formed as a by product.
The chemical composition of urea-formaldehyde (UF) polymer is [(O)CNHCH2NH]n in repeat units
Worldwide, about 20 million metric tons of UF are produced annually. Over 70% of this production is then put into use by the forest-products industry for bonding particleboard, MDF, plywood, and laminating adhesive.
It’s also used in agriculture as a slow release nitrogen fertilizer.