Can i ask to get chat restricted?

Riot doesn't currently grant chat restrictions on request, sorry. However, there are some options that may help reduce your own negative chat behavior;

1. Mute negative players immediately. Don't let them talk shit any more than you want to listen to; stopping them after the first line of bullshit will usually deescalate the situation so that you don't feel like responding to it.
2. Type /mute all at the beginning of each match. This is a more extreme measure, but some people find it necessary to stop even that first line of bullshit. There's also an option in the settings to turn off /all chat.
3. Move the chat window off the screen. That window holds good information outside of player chat so I don't advise this, but it could be useful for you even though it's more extreme than #2.
4. Edit your config file to shrink the chat window down to nothing. Down to -150 should make it effectively invisible, and you won't have to move it off your screen. This takes a little work and isn't a bannable modification, and if you change the size slider in-game it'll pop back up.
5. Rebind your Enter key. You can use 3rd party keyboard software (such as that inherent in most gaming keyboards) to place your Enter key somewhere else, or nowhere, so that it's hard or impossible to send a message. Profile options allow this to be easily switched on and off between games.

The best, so far, is turn off /all Chat. I wish there was a way to turn off both /all and team chat as well...just don't want to see the flames. With smart pings, it isn't really needed anymore.