On Friday the court said Frans van Anraat, 63, supplied the raw materials knowing that they would be used to make poison gas by Saddam Hussein's Iraq in the 1980-1988 war with Iran.
Poison gas was also used against Iraq's own Kurdish population, including an attack on the town of Halabja in 1988.
Van Anraat was acquitted of genocide charges.
Roel van Rossum, the presiding judge, said: "His deliveries facilitated the attacks and constitute a very serious war crime. He cannot counter with the argument that this would have happened even without his contribution.
"Even the maximum sentence is not enough to cover the seriousness of the acts."
Defence lawyers said they would appeal against the sentence, which was the maximum that could be imposed for the charge.
Jan Pieter van Schaik, a defence lawyer, said: "We believe that the court interpreted several points too conveniently."
He said it had not been proved that Van Anraat's materials had actually been used in poison gas attacks.
Van Anraat, who was not present in court, was acquitted of genocide charges because it could not be proved that he knew exactly how the chemicals would be used.
Relatives of Halabja victims
waited outside the court
But the judge did say the attacks had been carried out with the intent to destroy the Kurdish population in Iraq and had been part of a "policy of systematic terror" against them.
The Halabja attack on 16 March, 1988, killed an estimated 5000 people.
Dozens of relatives of victims and their supporters danced in a circle to the sounds of flutes and beating drums outside the court after the sentence was handed down.
More than 50, some in traditional dress, had followed the proceedings through interpreters into English, Farsi and Arabic and some clapped their hands when the sentence was read.
Banners on fences outside the court read: "The Hiroshima of Kurdistan is Halabja" and "Halabja genocide never again".
In a magazine interview in 2003, Van Anraat admitted supplying the chemicals but denied knowing that they were destined for Iraq and that they would be used to make poison gas.
He is the first Dutchman to be tried on genocide-related charges.
"... he wanted to resume exports of thiodiglycol almost immediately after he had seen footage of the gas attacks on Halabja... he did not regret or repent his acts"
Roel van Rossum,
The court said Van Anraat, acted as a middleman buying chemicals on the world market and selling them to Iraq despite export bans in the 1980s, acted "out of the love of profit".
The court said it was legally established that the businessman supplied chemicals including thiodiglycol and phosphorus oxychloride, both ingredients for mustard and nerve gases, to Iraq between 1985 and 1988.
Van Anraat was first arrested in Italy in 1989 on a United States warrant but later fled to Iraq where he lived for 14 years under a new name given to him by the Iraqi regime, Faris Mansour Rasheed al Bazzaz, meaning "the courageous and intelligent fabric salesman".
The judge said Van Anraat had shown no sign of remorse.
"The fact that he wanted to resume exports of thiodiglycol almost immediately after he had seen footage of the gas attacks on Halabja and told a colleague around July 1988 to tell no one he was in Baghdad shows he did not regret or repent his acts," the judge said.
Prosecutors said Van Anraat shipped chemicals from the United States to Belgium and from Belgium to Iraq via Jordan. He also shipped chemicals from Japan to Italy, and then overland to Iraq.
Fifteen Kurdish victims who joined the criminal trial were awarded 680 euros ($807.6) each in damages. Under Dutch law, civil parties can join criminal proceedings and win damages if the defendant is found guilty.