Recommender system based on purchase history, not ratings
You could use Content based filtering but then you have to intelligently pre process the data to extract all the contents of the products. Also, that might lead to leaving a some features, This article is a great head start after you preprocess all the data.

Also, you could make pseudo ratings for product vs a customer. That would depend on your problem statement. Some few suggestions could be the number of times the customer bought the particular product in last one month or you could also take an index which would define how frequently the customer buys that product which, mathematically would be last_two_purchases/interval_of_purchase or could also take an average of last few purchases and intervals. 

After making this pseudo rating you could convert all the content based features into numerical ones and use Latent factor model for collaborative filtering. Refer this video. Python could be used for this.