it's not ok. you'll need a booster blower made for this problem.
manufacturer Fantech says:
"When to boost a dryer.
Typical residential dryers are rated at 160cfm. However, boosting is
generally needed in order to maintain a minimum airflow of 100cfm as
duct length increases and bends are introduced in the duct line.
Based on surveying the recommendations from dryer manufacturers, and
local building codes in selected areas, dryer boosting is typically
required when the duct length exceeds the following:
Maximum duct length with:
No bends 25' 1 bend 20' 2 bends 15' 3 bends 10'
Fantech models DBF 110, DBF 4XL and RVF 4XL are all suitable for most
dryer boosting applications. Generally the models listed can be used
for maximum duct length of 60 linear feet with a maximum of six elbows
using four inch rigid duct. For longer duct runs please contact our
technical department for specific recommendations."
also, do not vent into a pipe you can't clean the lint out of.