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Application and preparation of modified polyisocyanate by CAPS (1135-40-6) 2018-06-08 10:15:08

In response to increasingly stringent environmental regulations, water-dispersible polyisocyanates have shown importance in various fields of application in recent years. Currently, water-dispersible polyisocyanates are mainly used as cross-linking agents for the preparation of water-soluble two-component polyurethane coatings (2K-PUR coatings), or as additives for aqueous dispersion adhesives, in textile finishing or non-Formaldehyde textile printing inks are used to crosslink aqueous dispersions(CN1429240A).


At present, water-dispersible polyisocyanates in most applications are non-ionic hydrophilic modifications via polyethers. Although such hydrophilically modified polyisocyanates have gained wide market recognition in most applications, there are also certain drawbacks such as their high viscosity, which requires applying a considerable shear force during the construction process in order to evenly distribute them into water medium. To circumvent the above drawbacks, researchers have attempted to prepare water-dispersible polyisocyanates by introducing ionic groups.


In the reported literature or patent, the ion-modified group includes carboxyl group, sulfuric acid group, hydroxyl group, hydroxysulfonic acid, etc., but there are still some defects, such as carboxyl-modified polymer prone to gelation, hydroxyl Sulfonic acid-modified products are obviously yellow in color. Later, Bayer reported on N-Cyclohexyl-3-Aminopropanesulfonic Acid (CAPS) modified polyisocyanate in its patent CN1429240A. It was found that CAPS-modified polyisocyanate can achieve fine dispersion in water and product storage stability. We briefly introduce a preparation example of this type of polyisocyanate as follows. 950 g of a polyisocyanate was stirred with 50 g of CAPS, 29 g of dimethylcyclohexylamine and 257 g of 1-methoxyprop-2-ylacetate under dry nitrogen atmosphere at 80 degrees centigrade for 5 hours, wherein the polyisocyanate was based on HDI containing isocyanurate groups, the NCO content is 21.7%, the average NCO functionality is 3.5, the monomeric HDI content is 0.1% and the viscosity is 3000 mPas. After cooling to room temperature, a colorless and transparent polyisocyanate solution can be obtained.


In summary, CAPS-modified polyisocyanates show certain advantages over other ionic or non-ionic modified products. In addition, with the increasingly stringent environmental protection requirements and people's increasing awareness of environmental protection, the future market acceptance of waterborne coatings will gradually surpass solvent-based coatings. In 2016, the market share of water-based coatings in China is only about 10%, and the future market space is huge.


Edited by Suzhou Yacoo Science Co., Ltd.

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