I used to work 9am-6pm previously. (Now I've switched to working part-time.)
Is there a fridge at your office? You need to get a plastic box to store your expressed milk to avoid contamination with other stuff in the fridge.
When I arrived at my office in the morning, I would put an ice-pack in the freezer. During lunch, I would pump milk and store the bottle in the fridge. Upon leaving work, I put the milk and the ice-pack in a Tommee-Tippee storage bag (around $100). The travelling time to home was around 20 minutes. The milk was still very cold when I reached home.
How long does it take you to travel from work to home?