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Polyurethane adhesive and paint crosslinking agent
2017-8-23 11:18:35
Polyurethane adhesive and paint crosslinking agent
Crosslinking agent is an important part of the polyurethane adhesives and coatings, crosslinking agent widely used at present domestic coating is 100 N type (HDI biuret crosslinking agent), TDI and TDI and small molecules polyols as TMP adduct.
As a new generation of advanced polyurethane adhesives and coatings crosslinking agents, HDI trimers with isocyanurate are increasingly valued.
HDI trimer is a polyisocyanate cross-linking agent of HDI under the action of the catalyst, and the theoretical energy is 3, and the quality fraction of isocyanate root is 25%. However, due to the selectivity of the catalyst and the limitations of the reaction conditions, the usually obtained tripolymer is a mixture of multiple components, the actual functional energy is greater than 3, and isocyanate root mass fraction is less than 25%.
The synthesis mechanism, catalyst, properties and application of HDI trimer are introduced on the basis of reference.
The self-clustering mechanism of HDI. In isocyanates, the electron density of nitrogen and oxygen is high and electronegative. The electron cloud density of carbon is small and positive, so carbon becomes the electrophilic center, vulnerable to the attack of nucleophilic reagents. Under the action of catalyst, isocyanates are added to each other, causing polymerization reactions. The following formula represents the general mechanism of HDI autopolymerization, where a-b represents the catalyst.
As you can see, there are many active intermediates, and the reaction of HDI can form different reaction products, along with the change of external conditions, since the HDI products from the mass fraction of each component in the different, isocyanate root mass fraction also have differences.
HDI's self-agglomeration products include trimer, dimer, carbonization diimide, linear polymeric and annular poly. The final product mainly depends on which active intermediate is dominant.
In HDI's self-polymerization products, there is a certain amount of cyclic polymerization, which leads to the lower quality fraction of the product isocyanate than the theoretical value. The formation of cyclic polymerization is caused by the secondary reaction of the active intermediates of the trimer, and there is evidence that the trimer generated by the reaction can further react with the reactive intermediate.
HDI self-polymerization catalyst. The catalyst in the literature report can be divided into the following categories:
Metal salt catalyst. Alkali metal salts used as isocyanate early base and the reaction catalyst, for HDI, alkali metal salt and the advantage of transition metal salts is in 3 get together the product does not contain dimers, does not decompose to produce HDI monomer during storage.
Chinese name: Diethyl toluene diamine(DETDA)
Physical and chemical properties: light yellow transparent liquid, slightly soluble in water, soluble in alcohols, ethers, ketones and other polar organic solvents, and polyether, polyester polyol compatibility.
Density 1.022
Viscosity (20 ℃) ??mPa·ss290±10
Pour Point ℃-9
Boiling point of310°C
Crosslinking agent is an important part of the polyurethane adhesives and coatings, crosslinking agent widely used at present domestic coating is 100 N type (HDI biuret crosslinking agent), TDI and TDI and small molecules polyols as TMP adduct.
As a new generation of advanced polyurethane adhesives and coatings crosslinking agents, HDI trimers with isocyanurate are increasingly valued.
HDI trimer is a polyisocyanate cross-linking agent of HDI under the action of the catalyst, and the theoretical energy is 3, and the quality fraction of isocyanate root is 25%. However, due to the selectivity of the catalyst and the limitations of the reaction conditions, the usually obtained tripolymer is a mixture of multiple components, the actual functional energy is greater than 3, and isocyanate root mass fraction is less than 25%.
The synthesis mechanism, catalyst, properties and application of HDI trimer are introduced on the basis of reference.
The self-clustering mechanism of HDI. In isocyanates, the electron density of nitrogen and oxygen is high and electronegative. The electron cloud density of carbon is small and positive, so carbon becomes the electrophilic center, vulnerable to the attack of nucleophilic reagents. Under the action of catalyst, isocyanates are added to each other, causing polymerization reactions. The following formula represents the general mechanism of HDI autopolymerization, where a-b represents the catalyst.
As you can see, there are many active intermediates, and the reaction of HDI can form different reaction products, along with the change of external conditions, since the HDI products from the mass fraction of each component in the different, isocyanate root mass fraction also have differences.
HDI's self-agglomeration products include trimer, dimer, carbonization diimide, linear polymeric and annular poly. The final product mainly depends on which active intermediate is dominant.
In HDI's self-polymerization products, there is a certain amount of cyclic polymerization, which leads to the lower quality fraction of the product isocyanate than the theoretical value. The formation of cyclic polymerization is caused by the secondary reaction of the active intermediates of the trimer, and there is evidence that the trimer generated by the reaction can further react with the reactive intermediate.
HDI self-polymerization catalyst. The catalyst in the literature report can be divided into the following categories:
Metal salt catalyst. Alkali metal salts used as isocyanate early base and the reaction catalyst, for HDI, alkali metal salt and the advantage of transition metal salts is in 3 get together the product does not contain dimers, does not decompose to produce HDI monomer during storage.
Chinese name: Diethyl toluene diamine(DETDA)
Physical and chemical properties: light yellow transparent liquid, slightly soluble in water, soluble in alcohols, ethers, ketones and other polar organic solvents, and polyether, polyester polyol compatibility.
Density 1.022
Viscosity (20 ℃) ??mPa·ss290±10
Pour Point ℃-9
Boiling point of310°C
Flash Point°C161.1°C
But under the action of the polymerization is quite heavy, unable to effectively control, easy to cause deep polymerization, polymer mass fraction in the product increased, isocyanate root of the products, low mass fraction, high viscosity, and tile products often have appeared; Another must be added at the end of the reaction, such as benzoyl chloride, p-toluene sulfonic acid, inorganic acid to terminate the reaction such as phosphoric acid, so that there will be insoluble in the formation of metal salts of product result in product tourne. To remove these metal salts, you must add a large amount of solvent diluted filtration, and then evaporate the solvent.
DABI et al, such as tributyl oxide, tetrabutyl oxide, tetrabutyl oxide, aluminum naphthenate, and cobalt naphthenate, etc., reacted at high temperature, and obtained the tripolymerization of the ideal structure. The analysis data shows that, under the action of three butyl oxide tin, the trimer is first produced, and only after the majority of HDI is consumed, the formation of poly body is formed.
Composite catalyst. The metal salts and phenol of long chain fatty acids work together, which can be obtained by HDI's self-agglomeration, and the termination agent should be added at the end of the reaction. Piperazine and its derivatives are also reported as catalysts for HDI self-polymerization. But piperazine has a carcinogenic effect, and the polymerization reaction has a period of several hours of induction, and the polymerization reaction starts to heat up violently and cannot be polymerized, and the solvent must be added to control the reaction.
The crosslinking agent for thermosetting powder coating is the most important part of coating composition. They can produce the production, storage and application of coatings, such as extrusion temperature, storage stability, crosslinking time, crosslinking temperature and flow property, impact resistance and hardness, weather resistance and chemical resistance, and so on.
Crosslinking agents and film-forming resins are sometimes difficult to distinguish, since these two components eventually form a complete adhesive system. Low molecular weight compounds in the adhesive system are often treated as cross-linking agents.
Copyright: Zhang Jia Gang YaRui Chemical co.,Ltd
But under the action of the polymerization is quite heavy, unable to effectively control, easy to cause deep polymerization, polymer mass fraction in the product increased, isocyanate root of the products, low mass fraction, high viscosity, and tile products often have appeared; Another must be added at the end of the reaction, such as benzoyl chloride, p-toluene sulfonic acid, inorganic acid to terminate the reaction such as phosphoric acid, so that there will be insoluble in the formation of metal salts of product result in product tourne. To remove these metal salts, you must add a large amount of solvent diluted filtration, and then evaporate the solvent.
DABI et al, such as tributyl oxide, tetrabutyl oxide, tetrabutyl oxide, aluminum naphthenate, and cobalt naphthenate, etc., reacted at high temperature, and obtained the tripolymerization of the ideal structure. The analysis data shows that, under the action of three butyl oxide tin, the trimer is first produced, and only after the majority of HDI is consumed, the formation of poly body is formed.
Composite catalyst. The metal salts and phenol of long chain fatty acids work together, which can be obtained by HDI's self-agglomeration, and the termination agent should be added at the end of the reaction. Piperazine and its derivatives are also reported as catalysts for HDI self-polymerization. But piperazine has a carcinogenic effect, and the polymerization reaction has a period of several hours of induction, and the polymerization reaction starts to heat up violently and cannot be polymerized, and the solvent must be added to control the reaction.
The crosslinking agent for thermosetting powder coating is the most important part of coating composition. They can produce the production, storage and application of coatings, such as extrusion temperature, storage stability, crosslinking time, crosslinking temperature and flow property, impact resistance and hardness, weather resistance and chemical resistance, and so on.
Crosslinking agents and film-forming resins are sometimes difficult to distinguish, since these two components eventually form a complete adhesive system. Low molecular weight compounds in the adhesive system are often treated as cross-linking agents.
Copyright: Zhang Jia Gang YaRui Chemical co.,Ltd
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