SLF4J MDC duplicate for two request

I have a web application. My application deployed by Tomcat. I write a Servlet Filter for put some data in MDC class at SLF4J By following code:

MDC.put("Id", UUID.randomUUID().toString();

My problem is : When I run my application for second or third request I get duplicare uuid . This scenario is serial and isn't concurrent. I think exist a thread pool that thread context don't clear.