News Details
Waterborne polyurethane coatings crosslinking agent
2017-4-13 23:06:50
Waterborne polyurethane coatings crosslinking agent,In recent years, the research and development of waterborne pu coatings and active, because of the waterborne polyurethane coatings is one of the important developing direction of environment friendly polyurethane coating.
However, waterborne polyurethane coating is dedicated to crosslinking agent is relatively rare, it is environmentally friendly polyurethane coating is an important development field of crosslinking agent.
Along with the people environmental protection consciousness of growing and increasingly strict environmental protection laws and regulations, promote domestic environmental protection coating, not only has the good social efficiency, also will produce the huge economic benefits. The Chinese paint industry is in rapid development period, a great potential for development and application. Relevant laws and regulations to the chemical industry must pay attention to environmental protection problems in the development of products, so researchers must speed up the development and promotion of solvent-free or high solid content in polyurethane coating crosslinking agent.
The synthesis of waterborne polyurethane coating
Preparation methods of water-borne polyurethane is usually divided into external emulsification method and internal emulsification method two kinds. Plus emulsification method refers to an emulsifier, under strong shear force is mandatory to polyurethane particles dispersed in water, the method of but because of the law exists large dosage of emulsifier, reaction time and the emulsion particle coarse, the resulting product quality is poor, shortcomings and so on rubber physical and mechanical performance is not good, so the current production basic need not the law.
Internal emulsification method is also called the emulsification method, is to point to in the molecular structure of polyurethane is hydrophilic group to make their own need for emulsifier dispersed emulsion method, thus become the waterborne polyurethane production and research of the main methods. Internal emulsification method and can be divided into acetone method, pre polymers mixing method, melt dispersion method, ketone imide/ketone nitrogen method, protect the emulsification method.
Acetone method. First synthesis with - NCO terminal base of high viscosity of polyurethane pre polymers, acetone solution, its viscosity is reduced, and then use an ion group chain extender chain extension agent, through strong shear force under high speed stirring to disperse in water, emulsion vacuum distillation after removing the solvent of acetone, waterborne polyurethane dispersion.
Acetone method of easy operation, good repeatability, variable a wide range of waterborne polyurethane molecular weight, the size of the particle size control, product quality is good, is currently the main method of production of waterborne polyurethane. But this method is to use low boiling point of acetone, easy to cause environmental pollution, process complex, high cost, low safety, is not conducive to industrial production.
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
Pre polymers hybrid method.
First synthetic containing hydrophilic group and end - NCO pre polymers, when relative molecular weight is not too high in the process of the polymers and the viscosity is small, can not add or add a small amount of solvent, under the high speed stirring dispersion in water, then use the hydrophilic monomer (diamine or three amine) should be part of the chain extender, generate high relative molecular weight of water-borne polyurethane urea.
End up with waterborne polyurethane dispersion. For the synthesis of low viscosity pre polymers, usually choose aliphatic or alicyclic isocyanate, because these two kinds of many isocyanate low reactivity, pre polymers when dispersed in water after using diamine extender chain is affected by water.
But pre polymers mixed dispersion process must be carried out at low temperature, in order to reduce the reactivity of - NCO and water; Must strictly control the viscosity of polymers, or pre polymers will be very difficult when dispersed in water, pre polymers blending method to avoid the use of organic solvent, simple process, convenient for industrialized continuous production. Defect is extender chain reaction occurs in the multiphase system, reaction can't according to quantitative manner.
Molten dispersion is also called the dispersion of melt polycondensation method, preparation of waterborne polyurethane is a kind of solvent-free method. This method is the addition polymerization of isocyanate and polycondensation reaction of amino closely together. With synthesis ionic hydrophilic groups and first - NCO terminal base polyurethane prepolymer, prepolymer with urea addition polymerization of ionic groups end double biuret urea based polyurethane oligomer.
The oligomer in the molten state and formaldehyde solution polycondensation reaction and hydroxyl methylation, formation of polyurethane containing hydroxyl methyl double biuret, diluted with water, stability of aqueous polyurethane dispersion.
Copyright: Zhang Jia Gang YaRui Chemical co.,Ltd
Diethyl toluene diamine(DETDA) http://www.yaruichem.com
However, waterborne polyurethane coating is dedicated to crosslinking agent is relatively rare, it is environmentally friendly polyurethane coating is an important development field of crosslinking agent.
Along with the people environmental protection consciousness of growing and increasingly strict environmental protection laws and regulations, promote domestic environmental protection coating, not only has the good social efficiency, also will produce the huge economic benefits. The Chinese paint industry is in rapid development period, a great potential for development and application. Relevant laws and regulations to the chemical industry must pay attention to environmental protection problems in the development of products, so researchers must speed up the development and promotion of solvent-free or high solid content in polyurethane coating crosslinking agent.
The synthesis of waterborne polyurethane coating
Preparation methods of water-borne polyurethane is usually divided into external emulsification method and internal emulsification method two kinds. Plus emulsification method refers to an emulsifier, under strong shear force is mandatory to polyurethane particles dispersed in water, the method of but because of the law exists large dosage of emulsifier, reaction time and the emulsion particle coarse, the resulting product quality is poor, shortcomings and so on rubber physical and mechanical performance is not good, so the current production basic need not the law.
Internal emulsification method is also called the emulsification method, is to point to in the molecular structure of polyurethane is hydrophilic group to make their own need for emulsifier dispersed emulsion method, thus become the waterborne polyurethane production and research of the main methods. Internal emulsification method and can be divided into acetone method, pre polymers mixing method, melt dispersion method, ketone imide/ketone nitrogen method, protect the emulsification method.
Acetone method. First synthesis with - NCO terminal base of high viscosity of polyurethane pre polymers, acetone solution, its viscosity is reduced, and then use an ion group chain extender chain extension agent, through strong shear force under high speed stirring to disperse in water, emulsion vacuum distillation after removing the solvent of acetone, waterborne polyurethane dispersion.
Acetone method of easy operation, good repeatability, variable a wide range of waterborne polyurethane molecular weight, the size of the particle size control, product quality is good, is currently the main method of production of waterborne polyurethane. But this method is to use low boiling point of acetone, easy to cause environmental pollution, process complex, high cost, low safety, is not conducive to industrial production.
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
Pre polymers hybrid method.
First synthetic containing hydrophilic group and end - NCO pre polymers, when relative molecular weight is not too high in the process of the polymers and the viscosity is small, can not add or add a small amount of solvent, under the high speed stirring dispersion in water, then use the hydrophilic monomer (diamine or three amine) should be part of the chain extender, generate high relative molecular weight of water-borne polyurethane urea.
End up with waterborne polyurethane dispersion. For the synthesis of low viscosity pre polymers, usually choose aliphatic or alicyclic isocyanate, because these two kinds of many isocyanate low reactivity, pre polymers when dispersed in water after using diamine extender chain is affected by water.
But pre polymers mixed dispersion process must be carried out at low temperature, in order to reduce the reactivity of - NCO and water; Must strictly control the viscosity of polymers, or pre polymers will be very difficult when dispersed in water, pre polymers blending method to avoid the use of organic solvent, simple process, convenient for industrialized continuous production. Defect is extender chain reaction occurs in the multiphase system, reaction can't according to quantitative manner.
Molten dispersion is also called the dispersion of melt polycondensation method, preparation of waterborne polyurethane is a kind of solvent-free method. This method is the addition polymerization of isocyanate and polycondensation reaction of amino closely together. With synthesis ionic hydrophilic groups and first - NCO terminal base polyurethane prepolymer, prepolymer with urea addition polymerization of ionic groups end double biuret urea based polyurethane oligomer.
The oligomer in the molten state and formaldehyde solution polycondensation reaction and hydroxyl methylation, formation of polyurethane containing hydroxyl methyl double biuret, diluted with water, stability of aqueous polyurethane dispersion.
Copyright: Zhang Jia Gang YaRui Chemical co.,Ltd
Diethyl toluene diamine(DETDA) http://www.yaruichem.com
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