Thanks for replying. I understand that I made an error inserting "end" property.
What I tried to do was delay, of same pixel, an animation of the same timeline (for example animate ".section_1_01" after 500px of scroll from the ending of ".section_1" animation). In which way I can do it?
To return to the subject of the internet explorer, my problem is that the website on IE have extra spaces and different position of other browsers and I don't know why.
Probably the best solution is just like you said, drop IE support.