Method for preparing paraformaldehyde

A paraformaldehyde and formaldehyde solution technology, applied in the field of preparation of paraformaldehyde, can solve the problems that the polymer cannot be fully decomposed into polyoxymethylene monomers, the molecular weight can not be uniformly distributed, and the polymerization activity can not be reduced. , to reduce the formation of insoluble matter, prolong the storage time, and avoid the growth of molecular chains

Active Publication Date: 2010-09-29
WANHUA CHEM GRP CO LTD +1
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

However, the traditional single amine basic catalysts used at home and abroad have low catalytic activity, which cannot ensure that the polymer in the formaldehyde solution is preferentially decomposed into polyoxymethylene monomers; In the process, the polymerization activity between the polyoxymethylene alcohol monomers in the formaldehyde solution cannot be reduced, the uniform distribution of the molecular weight cannot be guaranteed, the degree of polymerization is high (the degree of polymerization of the obtained product ranges from 30 to 100), and the product stability is poor , cannot meet the needs of paraformaldehyde downstream high-end industries (such as high-end automotive paint and other fields)
[0004] Patent US5898087 discloses a method for preparing paraformaldehyde, during which it is disclosed that an amine or a mixture of amine and sodium hydroxide is added to a hot formaldehyde solution to improve the stability of the paraformaldehyde product, and a lower alcohol is added while adding the amine , in which the lower alcohols only play the role of strengthening the effect of amine catalysts, the stability of the obtained product is not high, and the solubility of the product in water decreases after storage for a period of time

Method used

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Examples

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Embodiment 1

[0057] The formaldehyde solution is concentrated to 75wt% concentrated formaldehyde solution, then pumped into a buffer tank equipped with stirring and heating devices, the temperature in the buffer tank is maintained at 98 ° C, and 80 g of methanol is added to 1000 g of the above-mentioned concentrated formaldehyde solution , after stirring and mixing for 0.5 hours, add 0.5 g of a catalyst compounded by triethanolamine and diethanolamine according to the mass ratio of 1:2, and after stirring and mixing for 0.5 hours, a reaction product is obtained, and the acidic substance content in the reaction product is ≤30ppm , and then pump the reaction product to a multi-stage fluidized bed cascade spray drying system for drying to obtain paraformaldehyde solid particles with an aldehyde content of 95.4%. The degree of polymerization of the final product is 10. After 100 days at room temperature, the The solubility of the product in water is 100%, so the product can be stored at room te...

Embodiment 2

[0059] The formaldehyde solution is concentrated into 80wt% concentrated formaldehyde solution, then pumped into a buffer tank equipped with stirring and heating devices, the temperature in the buffer tank is maintained at 95°C, and 50g of methanol is added to 1000g of the above-mentioned concentrated formaldehyde solution , after stirring and mixing for 0.2 hours, add 0.3 g of a catalyst compounded by triethanolamine, ethanolamine and diethylamine according to the mass ratio of 3:1:1, and stir and mix for 1 hour to obtain a reaction product, in which The acidic substance content is ≤ 50ppm, and then the reaction product is pumped to a single-stage fluidized bed cascade spray drying system for drying to obtain paraformaldehyde solid particles with an aldehyde content of 96.3%, and the degree of polymerization of the final product is 12. After 120 days of storage under high temperature, the solubility of the product in water is 100%, that is, the product at room temperature can ...

Embodiment 3

[0061] The formaldehyde solution is concentrated into 85wt% concentrated formaldehyde solution, then pumped into a buffer tank equipped with stirring and heating devices, the temperature in the buffer tank is maintained at 102°C, and 50 g of the above-mentioned concentrated formaldehyde solution is added according to The mixture of methanol and propanol compounded at a mass ratio of 2: 1 was stirred and mixed for 4 hours to obtain a reaction product. During the process of pumping the reaction product to the drying system, 0.7 g of diethanolamine and tris Ethylamine is a catalyst compounded according to a mass ratio of 1:1, and mixed by a mixer, the acidic substance content in the resulting mixture is ≤ 60ppm, and the mixture is pumped to a multi-stage fluidized bed cascade spray drying system for drying, Obtained paraformaldehyde solid particles with an aldehyde content of 95.4%, the degree of polymerization of the final product is 9, and after storage at room temperature for 1...

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Abstract

The invention provides a method for preparing paraformaldehyde. The method comprises the following steps of: concentrating formaldehyde solution to between 75 and 85 weight percent, and pumping the concentrated formaldehyde solution to a buffer tank; adding a polymerization inhibitor and a catalyst into the buffer tank in turn, wherein the reaction temperature in the buffer tank is between 90 and 110 DEGC and the average residence time of the materials in the buffer tank is 0.1 to 5 hours; and performing polymerization reaction on the concentrated formaldehyde solution, and drying the obtained reaction product to obtain a paraformaldehyde product with low polymerization degree. The method has the advantages of simple operation and low equipment investment; and the aldehyde content of the paraformaldehyde obtained by using the method meets the requirement of high-end industries, and the paraformaldehyde has the advantages of low polymerization degree and stable quality.

Description

technical field [0001] The invention relates to a method for preparing paraformaldehyde, in particular to a method for preparing paraformaldehyde with a low degree of polymerization from a formaldehyde solution. Background technique [0002] Paraformaldehyde (PF) is an industrially important linear formaldehyde polymer with the molecular formula HO(CH 2 O) n H, is a mixture of n = 8 to 100 units of polyoxymethylene glycol, it is usually a colorless crystalline solid with a strong formaldehyde smell, insoluble in ethanol, acetone and ether, soluble in dilute acid and Dilute alkaline solution. [0003] At present, the production methods of paraformaldehyde at home and abroad are mainly divided into two types: rake drying and spray drying, which are vacuum rake drying and fluidized bed spray drying respectively. The polymerization mechanism of paraformaldehyde solution shows that the equilibrium distribution of formaldehyde oligomeric species depends on the formaldehyde conc...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C08G2/08C08G2/04C08G2/06
Inventor 陈斌华卫琦尚永华卢志刚钟政丁建生
Owner WANHUA CHEM GRP CO LTD
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