A kind of preparation method of melamine cardanol modified curing agent

Abstract

The invention discloses a preparation method of a melamine-cardanol modified curing agent, which comprises the following steps in parts by weight: mixing 140-155 parts of cardanol, 28-40 parts of paraformaldehyde and 5-15 parts of melamine evenly , drop 20-110 parts of amine compounds and control the temperature to react at 30-50 ° C, after the dropwise addition is completed, keep the temperature and continue to react for 1-3 hours, then add 140-155 parts of cardanol and 28-40 parts of paraformaldehyde , control the temperature and add 20-110 parts of amine compounds dropwise at 40-50 ℃, after the dropwise addition, keep the temperature and continue the reaction for 1-3 hours, then add an organic solvent to the reaction solution, stir and mix evenly, keep the temperature at rest The layers are separated to obtain an upper organic phase and a lower aqueous phase; the obtained upper organic phase is subjected to vacuum distillation to obtain the melamine cardanol modified curing agent. The modified cardanol curing agent product prepared by the invention has no turbidity phenomenon when placed for 6 months, does not affect the surface smoothness of the paint film during application, and achieves good results.

Description

technical field [0001] The invention relates to a preparation method of a melamine cardanol modified curing agent. Background technique [0002] Cardanol is a kind of natural cashew nut shell oil extracted by advanced technology, which can replace or partially replace phenol to manufacture epoxy curing agent, liquid phenolic resin, liquid or powder thermosetting phenolic resin. [0003] At present, my country is a country with a large demand for cardanol, and it is also the main importer of cashew nut shell liquid in the international market. Due to the renewability of cardanol, more and more attention is paid to it, which can save social resources. The application of cardanol is mainly the preparation of cardanol curing agent. The prepared curing agent and epoxy resin are cured at high temperature to obtain a paint film with corrosion resistance, high temperature resistance and good operation at low temperature. The film is mainly used in the coating of paint film on ships...

AI Technical Summary

Problems solved by technology

At present, the main domestic manufacturers of cardanol curing agent synthesis are: Shanghai Meidong Biomaterials Co., Ltd., Cardolite Zhuhai Co., Ltd., etc., they mainly use cardanol, aldehydes (formaldehyde, paraformaldehyde, paraformaldehyde), polyamines (or mixed amine) carries out Mannich reaction and makes cardanol solidifying agent, exothermic heat is too violent when adding paraformaldehyde to carry out reaction due to one-time addition, and operation risk is very high; Therefore usually adopt the method for adding paraformaldehyde in batches, After the reaction, excess polyamines and aldehydes and the water produced by the reaction have the following defects in this process: the amine compounds (polyamines) are substantially excessive in the reaction process, and when the reaction is completed, the vacuum distillation process is basically Difficult to clean amine compounds (polyamines)

Secondly, when amine compounds (polyamines) use small molecular amines, there are still the following disadvantages: small molecular amines are highly volatile and toxic, and the residual small molecular amine compounds affect the paint film performance of the product, resulting in the appearance of the paint film. There are serious defects such as oily surface and white film

In the process of this preparation method, cardanol, paraformaldehyde, melamine and amine compounds undergo Mannich reaction, and the reaction temperature is 80-90°C. At such a high temperature, a large amount of melamine will undergo its own polymerization side reaction, A large amount of dimer and polymer products are produced, the self-polymerization product of melamine is solid and remains in the product, and the self-polymerization product of melamine is a fine solid, which is difficult to separate from the modified cardanol curing agent product, and filtered After being placed for 3 days, there is still solid precipitation, and there is still solid precipitation at low temperature, and the product after precipitation is turbid. Although there is a melamine curing agent in the modified cardanol, the product is turbid and cannot be applied to the smear layer. There is a large amount of Turbidity, which will affect the surface smoothness of the paint film when applied

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