I brought my pump to work. forgotten to bring enough storage containers to pump my milk. after the 1st pump, I pout into storage bag. then can I freeze the container after use (without wash?) for 2nd pump?

Yes. After my 1st pump at work, I’ll store my flanges & bottles in a ziplock bag (without washing) & keep it cool in the fridge for the 2nd pump in the afternoon. To wash it after every pump at work is quite a hassle, so that would be the best option to me, as I wouldnt want to carry too many spare parts to office daily.. :)