Staff had submitted a cost-saving plan to the American-owned firm
Staff at the Air Products factory near Wrexham have been told the site is to close, with the loss of 200 jobs.
The company, which plans to move production of gas plant equipment to China, said the decision to close the plant was made with "great sadness".
Workers at the factory, who have helped train staff in China, had launched a Downing Street petition to save jobs.
The Unite union said it was disappointed and would seek to maintain a manufacturing base at Wrexham.
Union officials and staff met with management at the plant earlier this month in the hope of securing a deal to save it.
However, on Tuesday, Laurence O'Donnell, the factory's general manager, said: "It is with great sadness that today we announced to our people the decision to close our manufacturing facility in Acrefair, north Wales.
"We recognise the impact this will have on our employees, their families and the local community.
"We will now continue to consult with them regarding the impact of this decision.
Air Products supplies items such as gas used in the welding process
"We will also be working with organisations such as Job Centre Plus to put in place dedicated support for our employees."
Mr O'Donnell said employees had put forward a "comprehensive and thorough" counter-proposal, and the company had held talks with MPs, AMs and Wrexham council.
He said the decision had been made "in response to on-going cost pressures and the changing demand for our products which is shifting to other parts of the world, notably Asia".
He added: "Our manufacturing facility in Acrefair has a tradition of great workmanship and professionalism. I would like to pay tribute to our employees for their unceasing commitment throughout this time."
The plant, which opened in 1950, employs 140 craftsmen and 50 in management and administration.
Graham Rogers, of the Unite Union, said: "It goes without saying that we're disappointed.
"We will be holding a meeting on site next week in relation to whether or not we can meet with MPs to discuss what they can do to maintain a manufacturing base in Wrexham, even if it means downsizing."
North Wales AM Janet Ryder said: "It's a black day for the local economy of Wrexham. We need to maintain these kind of skilled jobs and the research and development that was on-site at Acrefair.
"It will feel like a betrayal of a skilled workforce that has been consistently profitable for the parent company."
Air Products, an American-owned company, supplies gas and related equipment to a wide range of industries.
Its products include equipment for air separation, natural gas liquefaction and hydrogen purification.
Martyn Jones, MP for Clwyd South, said: "Today's decision is a big blow, there can be no doubt about that.
"None of us wanted it to come to this.
"But in co-operation with local trade unions and local job centres every measure possible to curb the effect of the recession is being put into place."