The present invention is directed to stable, aqueous dispersions of polyurethane-ureas which are formed by
a) preparing isocyanate-terminated prepolymers containing about 5 to 190 milliequivalents per 100 grams of polyurethane-urea of chemically incorporated potential anionic groups and/or anionic groups and up to about 10% by weight, based on the weight of the polyurethane-urea, of lateral and/or terminal hydrophilic chains containing ethylene oxide units,
b) converting a sufficient amount of the potential anionic groups to anionic groups either before, during or after preparing the prepolymer such that the blend of step (c) can be stably dispersed in water, wherein at least about 50% of the counterions of the anionic groups are derived from volatile organic compounds,
c) blending said prepolymer either before, during or after step (b) with an epoxy resin which is not dispersible in water and contains at least one epoxide group, such that the equivalent ratio of potential anionic groups and anionic groups having counterions derived from volatile organic compounds to epoxide groups, is about 0.2 to 20.0,
d) dispersing the blend of prepolymer and epoxy resin in water and
e) chain extending said dispersed blend with a polyamine having an average functionality of about 2.0 to 6.0 in an amount sufficient to provide a ratio of amino groups to isocyanate groups of about 0.6:1.0 to 1.0:1.0.
The present invention is also directed to the use of the aqueous polyurethane-urea dispersions for the production of coated substrates having improved humidity resistance.
本发明涉及聚
氨酯-
脲的稳定
水性分散体,其形成方法如下
a) 制备
异氰酸酯封端预聚物,每 100 克聚
氨酯
脲中含有约 5 至 190 毫当量的
化学合成的潜在阴离子基团和/或阴离子基团,以及按聚
氨酯
脲重量计最多约 10%(含
环氧乙烷单元的侧向和/或末端亲
水链)、
b) 在制备预聚物之前、期间或之后,将足够量的潜在阴离子基团转化为阴离子基团,使步骤(c)的混合物能稳定地分散在
水中,其中至少约 50%的阴离子基团的反离子来自挥发性有机化合物、
c) 在步骤(b)之前、期间或之后,将所述预聚物与不能在
水中分散且含有至少一个环氧基团的环氧
树脂混合,使潜在阴离子基团和具有来自挥发性有机化合物的反离子的阴离子基团与环氧基团的当量比约为 0.2 至 20.0、
d) 将预聚物和环氧
树脂的混合物分散在
水中,并
e) 用平均官能度约为 2.0 至 6.0 的
多胺对上述分散混合物进行扩链,其用量足以使
氨基与
异氰酸酯基的比例达到约 0.6:1.0 至 1.0:1.0。
本发明的另一个目的是使用
水性聚
氨酯-
尿素分散体生产具有更好防潮性能的涂层基材。