Waterborne polyurethane (PU) is a water-soluble polyurethane polymer material that dissolves in a water-based complex solvent to form a water-soluble system. It has the advantages of being non-toxic, non-environmental, energy-saving, safe, and easy to operate; it also has a solvent-based polyurethane. Some important properties have been widely used in many fields such as printing inks, decorative coatings, printing and dyeing coatings, and adhesives. In recent years, environmental friendly fabric printing and dyeing coatings have attracted the attention of the printing and dyeing industry at home and abroad. The production of oleoyl diethanolamine from the aminolysis reaction of dry vegetable oil with diethanolamine, and its use of functional monomer dimethylol propionic acid ( DMPA) composes composite diol components, and TDI/HDI diisocyanate compound components are gradually added to polymerization to obtain room-temperature cross-linked waterborne polyurethane resin; and one-component polyurethane water-based paint suitable for screen printing and dyeing of fabrics is prepared. Studies have shown that the room temperature cross-linked waterborne polyurethane resin synthesized by the amine hydrolysis method can meet the manufacturing process requirements of the water-based screen printing and dyeing coating, and is suitable for the screen printing and dyeing of fabrics. The film formed by curing has high light and water resistance, strong adhesion, bright colors, and feel. Good, non-toxic, sticky and easy to adjust, is an excellent environmentally friendly screen printing and dyeing coating.
1 experiment
1.1 Raw materials
Vegetable oils, diethanolamine, toluene diisocyanate (TDl), sodium methoxide, dimethylol propionic acid (DMPA), cyclohexanone, ethylamine, driers, catalysts, are industrial products, hexamethylene diisocyanate ( HDl) (import),
Compound low-carbon alcohol ether solvent (homemade), distilled water, etc.
1.2 Preparation
1.2.1 Vegetable oleoyl-E alkanolamine Diethanolamine and sodium methoxide were added to a reaction vessel equipped with a stirring and reflux condenser. The mixture was heated to 90-100 °C until all sodium methoxide dissolved. Then the vegetable oil was added to the mixture under stirring, heated to 105-110, held for 4.5 hours, and the methanol solubility (25°C, 1:3 methanol completely dissolved) was measured. The amine solution reached the end point and was discharged for use.
1.2.2 waterborne polyurethane binder
Assemble the reaction device as required and check that the heating, stirring, condensation, temperature control, and sealing system are correct.
1.2.1 Synthetic plant oleoyl diethanol
Amine, DMPA, and cyclohexanone were successively added to the three-necked flask, stirring was started, and the temperature was increased. After the system was completely homogenous, the temperature was lowered to 20-30. The TDI/HDI mixture was added in three batches and added once every 15 minutes. Add the catalyst, control the reaction temperature at 70N80cC, keep warm for 4h; add compound low-carbon alcohol ether solvent, stir well, add ethylamine in batches to make it into salt, control the temperature below 70°C, wait until the system pH is 8.5N9.5 stable After adding driers to stir; add distilled water, adjust the viscosity of the system is stable and qualified after filtering out the material, to obtain room temperature cross-linked waterborne polyurethane resin solution that is waterborne polyurethane binder.
1.2.3 Waterborne Polyurethane Screen Printing Coatings
According to the formulating amount, the water-soluble polyurethane resin binder, pigment, filler, lower alcohol compound solvent, distilled water, and defoamer are weighed together and added to the predispersed container to stir, so that the solid powder such as pigment and filler is wetted and predispersed until The system has no solid powder and is then sent to a sand mill for grinding and dispersion. The temperature of the grinding material must not exceed 35 bars. When the fineness is 151xm or less and the viscosity is 6.5-7.5 Pa.s (25°C), color samples are taken. After comparison, the water-based polyurethane resin screen printing coating was obtained.
Results and discussion
Synthesis of Waterborne Polyurethane at Ambient Temperature and Curing Mechanism of Coating Film
At room temperature cross-linked water-based polyurethane synthesis, vegetable oil and diethanolamine are firstly formed into oleoyl diethanolamine under the action of CH30Na, and then used together with dimethylol propionic acid (DMPA) as a difunctional hydroxyl component, and the other is TDI/HDI. Difunctional isocyanate-based components, this bicomponent under certain conditions, through gradual addition copolymerization to generate polyurethane resin barrier due to the introduction of double bonds and carboxyl groups on the polymer side chain of polyurethane, the former makes the resin acting as a driers Under the normal temperature generated after cross-linked film, the latter gives the resin water solubility. In order to increase the water-solubility of the resin, the stability of the tree B from the liquid and the ink is improved, and the neutralizing agent is used to salt the carboxylic acid. Imprinting: The curing drying method of the dye coating includes the normal temperature oxidation cross-linking of the polyurethane side-chain double bond under the driers, the decomposition of the ammonium carboxylate salt of the polyurethane pendant group, and the volatilization of solvent water and cosolvent lower alcohol ethers in the system. With the infiltration, the oxidation cross-linking of the double bonds plays a major role in the curing speed of the printing film and the physical and mechanical properties of the dried film.
Factors Affecting Waterborne Polyurethane Synthesis
The water-solubility of the resin mainly depends on the carboxyl functional groups retained in the resin molecule. The resin acid value reflects the amount of carboxylic acid groups contained in the resin molecular structure, and also reflects the level of the functional monomer (DMPA) in the synthetic design of the waterborne polyurethane resin. The size of the acid directly affects the water solubility of the resin and the stability of the system. High acid value, good water-solubility of the resin, low viscosity of the system, and poor water resistance of the printing film. In the synthesis of polyurethane resin, the ratio design of the diisocyanate component to the hydroxyl component in the synthesis system is an important parameter. Different OH/NCO values ​​will affect the properties of the resin, such as viscosity, molecular weight, etc., and affect the resin. Film after film performance. When the amount of hydroxyl component is determined, the combination ratio of amine hydrolyzate and DMPA directly affects the water solubility and stability of the resin and the dryness of the ink, the amount of amine hydrolyzate is large, the water solubility of the resin is poor, the stability of the coating is poor, and the printing film is dry Good quality, high gloss, good water resistance; on the contrary, poor dryness, low gloss, good water solubility, good stability, poor film water resistance.
In order to adjust the flexibility and feel of the printing film, TDI and HDI monomers are used for compounding in the formula design. The resin prepared with TDI has high hardness, and the printing film is brittle and has poor flexibility due to the rigid benzene introduced into the polymer chain structure. The ring reduces the flexibility of the polyurethane polymer chain; the resin prepared with HDI has good flexibility, low hardness, and the printed film is soft, which is due to the low rotational free energy of the fatty chain segment, resulting in a decrease in the rigidity of the polyurethane polymer chain; TDI and HDI monomers are copolymerized to achieve rigidity and softness with complementary advantages. After comparative experiments, the process conditions for polyurethane synthesis are selected: the ratio of n(OH):n(NCO) is 1 to 1.2:1, and n(TDl):n(HDl) is 1.5:1-0. .6:1, the polymerization temperature is 70-80°C, the polymerization time is 1.5-2 hours, the resin acid value is 90-110 meKOH&, and the mole fraction x (catalyst) is 0.02%.
in conclusion
From the infrared absorption spectra of linseed oil and infrared absorption spectra of linolenic amine hydrolyzed products, it is known that the dry vegetable oil and diethanolamine react with amines to form oleoyl diethanolamine, which is composed of functional monomer dimethylol propionic acid (DMPA). Composite diol components, and TDI / HDI diisocyanate composite components by the gradual addition polymerization, to obtain room temperature cross-linked water: polyurethane resin, and made for a single-component polyurethane screen printing and dyeing waterborne polyurethane coatings. Studies have shown that the use ratio n (vegetable oil): n (diethanolamine) is 1:1, n(TDl):n(HDl) is 1.5:1-0.6:1, n(OH):n ( NCO) is a raw material ratio of 1.1:1 to 1.2:1, and the acid value is controlled at 99-110 mgKOH/g. The room-temperature crosslinkable waterborne polyurethane resin synthesized by this method can satisfy the manufacturing process of water-based screen printing and dyeing coatings. Requirements, suitable for fabric screen printing and dyeing operations, good quality. The water-based paint is colorful, feels good, non-toxic and safe. It is an excellent environmentally friendly screen printing and dyeing coating.