Not just after the invasion of Poland, right up until the invasion of the Soviet Union.

  On the Russian side, General Thomas, Chief of the German War Industry Department, recorded that “the Russians carried out their deliveries as planned, right up to the start of the attack. Even during the last few days, transports of India rubber from the Far East were completed by express transit trains.”³⁰
  This was not because the Russians did not expect to be attacked. As early as September 18, 1940, the Germans learned about anti-German propaganda in the Red Army, and interpreted it as a response to fear of attack by Germany.³¹ The Kremlin fulfilled its economic commitments to the end because it was determined to give Hitler no cause to attack. Until late in the day, also, the industrial and war materials received from Germany were a very important supplement to Russia’s armament efforts. The raw materials which Germany received were mostly perishable, while the arms and machines received by Russia remained when war came.

The Cold War & Its Origins, 1917-1960, Vol. I, Denna F. Flemming, 1961, Chapter 6.