As a preliminary note, 6 weeks is too young for a puppy to be away from mom. In some areas it is illegal to sell a puppy under the age of 8 weeks.
Personally, I wouldn't leave a 6 week old puppy in a crate unattended because they have little to no control over their bladders and you do not want to teach puppy that it's ok/necessary to eliminate in her bed.
My dogs are 4 and 7.5 and they are restricted to the kitchen when I'm away because they still get into mischief.
An ADULT dog should not be crated for more than 5-6 hours per day. A puppy should not be crated any longer than approx. 1 hour per month of age (ie. 3 month puppy = max crate time of 3 hours).
Alternatives to crating include exercise pens (I have a 4.5 foot high 10 panel pen) baby gates and puppy proofed rooms.
These alternatives are, in my opinion, much better for the dog because they have room to play and can have access to water and if there is an accident because of upset tummy or whatever, the dog isn't forced to lay in his mess for hours.