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Paraformaldehyde Production Technology

Country/Region china
Company Jiangsu Kaimao Chemical Technology Co., Ltd
Categories Lead Acid Battery Production Line
Telephone 519 86151507
ICP License Issued by the Chinese Ministry
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Paraformaldehyde Production Technology

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Paraformaldehyde Production Technology

After many years development, formaldehyde industry in China has made big progress in production scale, output, quality and technology, and has approached or reached the international advanced level in many aspects, however, the formaldehyde down stream productsParaformaldehyde has more development spaces.

Section A. Paraformaldehyde Properties

Paraformaldehyde, short form PF is a white powder form or particle form solid. It is an important linear polymer, molecular formula (CH2O)n,; molecular weight (30)n; density 1.39 (water=1.0), melting point: 120-170℃; flash point: 71℃; ignition temperature: 300-410℃; heat of combustion :510 KJ/molheat of formation:177 KJ/molvapor pressure:0.

19Kpa/25℃low explosion limit of powder dust: 40g/m3 .Paraformaldehyde will be slowly decomposed into gas form formaldehyde at ambient temperature and will form formaldehyde water solution. Therefore, it has general formaldehyde properties. Paraformaldehyde is a mixture of formaldehyde molecule and HO(CH2O)nH etc.

Paraformaldehyde can be divided into tow types which is low polymerization degree paraformaldehyde, and solid form paraformaldehyde. Mainly use polymerization degreen( the molecules number in the chain) for distinguishing, paraformaldehyde with low polymerization degree, in which, n<100, is easy dissolved in water; depolymerization thoroughly.

The product is loose form with uniform grains, which is the ideal raw material for formaldehyde, and is excellent replacement for industrial formaldehyde. Therefore it has big development value and potentials.

Section B. Paraformaldehyde Application

Paraformaldehyde is mainly used in
Pesticides: synthesis of acetochlor, butachlor, and glyphosate.
Medicine and pharmaceutics: produce vitamin A.
Coatings: synthesis of high grade automobile paint.
Resins: applied in resin production such as ion exchanging resin and melamine resin etc. Among them, 70-80% of paraformaldehyde are used to produce synthetic glyphosate herbicide; in resin industry, use paraformaldehyde to replace 37% of industrial formaldehyde to produce phenolic resin; not only can produce high quality thermoplastic and thermosetting phenolic resin, also can greatly reduce waste water discharge and lower materials consumption more than 10%.

Section C. Paraformaldehyde Production Process

So far, there are two paraformaldehyde production processes. One is vacuum Rake type drying process, another is spray drying process.

1.Harrow type drying process
Raw material formaldehyde is firstly concentrated and dehydrated until the formaldehyde concentration is increased from 37% to 65%then, it is sent to the vacuum Rake type dryer for further dehydration and drying to make powders. The whole drying process is operated under vacuum condition. The evaporation condensates contain 10-15% of diluted formaldehyde, which returned to formaldehyde shop to form 37% formaldehyde for sale or produce methylal or hexamine. It is batch form operation. Each batch feed for Rake type dryer is around 4-5m3drying time: 4-6 hours. This process has long production period, low capacity and the products are powder or block form.

2.Spray Drying Production Process
Formaldehyde concentration, through two stages of vacuum concentration, reaches 85%, then, is pumped to spray dryer. The concentrated formaldehyde is sprayed out to form particles of paraformaldehyde. This is a continuous process, in which, concentrated formaldehyde becomes to be solids within short time. It is able to form short linear formaldehyde molecule chain; as a result, product has good water solubility.

Section D. Low polymerization Degree Paraformaldehyde Production Technology

Low polymerization degree paraformaldehyde reaction is as following:
nCH2(OH)2 (CH2O)n + (n-1)H2O
To produce low polymerization degree paraformaldehyde must take care of the following issues:
Formaldehyde dehydration, polymerization, depolymerization must be performed at the same time in the formaldehyde concentration process. If process condition is not well controlled, it is easy to cause large amount of formaldehyde loss or formaldehyde polymerized to clog the system.
In the concentrating and drying process, if the formaldehyde concentration is not high enough, with relatively high water content; the product will be sticky and easy to be agglomerated.
Because the raw material formaldehyde contains small amount of methanol and formic acid polar molecules, in the concentration process, these materials will lead to further paraformaldehyde polymerization and form insoluble polymers.

1.Formaldehyde Concentration
Formaldehyde water solution is a co-polymerization mixing

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