A kind of tung oil-based waterborne polyurethane coating and preparation method thereof

Abstract

The invention discloses a preparation method of a tung oil-based aqueous polyurethane coating. The preparation method comprises the following steps: mixing tung oil, carboxylic acid, an acid catalyst and a hydroxylation reagent in proportion, and heating the obtained mixture to 35-45 DEG C; dropwise adding a hydrogen peroxide solution while intense stirring, controlling the dropwise adding speed to keep the reaction carried out at 40-65 DEG C, and keeping the reaction for 3-5 h after the dropwise addition is finished; standing and layering the obtained reaction solution after the reaction ends, separating the obtained water phase, neutralizing the water phase, washing the neutralized water phase with water, and carrying out reduced pressure distillation to obtain tung oil polyol; and uniformly mixing the tung oil polyol, a hydrophilic modifier and acetone in proportion, adding diisocyanate, carrying out a reaction at 50-70 DEG C for 2-5 h, cooling the obtained reaction product to room temperature, adding a neutralizer to form a salt, adding a diamine chain extender and deionized water mixed solution, carrying out a chain extension reaction until no free isocyanate radicals exist, and carrying out reduced pressure distillation to remove the acetone in order to obtain the tung oil-based aqueous polyurethane coating. The preparation method has the advantages of effective improvement of the hydrophobicity and the moisture resistance of the aqueous polyurethane coating, and renewable and nontoxic raw materials.

Description

technical field [0001] The invention belongs to the field of polyurethane materials, and in particular relates to a tung oil-based waterborne polyurethane coating and a preparation method thereof. Background technique [0002] With the depletion of fossil resources and the increasing awareness of environmental protection, social needs have put forward new requirements for the coatings industry, namely the development of new coatings with environmental protection, high performance, water-based solvent-free, high solids, powder and radiation curing. In the current coatings, polyurethane coatings are widely used, including general coatings, special coatings, industrial coatings, and architectural coatings. Water-based polyurethane uses water as a solvent, which is non-toxic, environmentally friendly, and energy-saving. It combines the advantages of high hardness, strong adhesion, and corrosion resistance of solvent-based polyurethane with the advantages of low VOC content of wa...

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Problems solved by technology

However, tung oil is used to prepare high-quality vegetable oil polyols. Because tung oil has a high degree of unsaturation and is the only unsaturated vegetable oil with conjugated double bonds in nature, the iodine value reaches more than 170, and more than 85% of the unsaturated bonds are Carbon-carbon conjugated triene bonds, so the presence of conjugated double bonds in tung oil during the preparation of polyol epoxidation makes the epoxy group highly reactive, poor in selectivity, and prone to side reactions, thereby generating macromolecular cross-links. Co-product, causing a sharp increase in viscosity, usually solid at room temperature and cannot be used for further synthesis of polyurethane products

Research literature (such as Epoxidation of Natural Triglycerides with Ethylmethyldioxirane, "Journal of the American OilChemists' Society", 1996, 73: 461-464) has investigated different vegetable oils, such as corn oil, soybean oil, sunflower oil, cottonseed oil, tung oil, etc. During the epoxidation process of saturated vegetable oil, it was also found that tung oil with only conjugated double bonds undergoes a crosslinking reaction during the epoxidation process, resulting in a sharp increase in viscosity and cannot be used to prepare polyurethane products

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