The owners of the Grangemouth complex said they believe there is "strong support" for the company as the deadline looms for workers to respond to a new business plan.
Staff at the central Scotland oil refinery and petrochemical plant have until 6pm today to decide whether to sign up to fresh terms and conditions proposed by owners Ineos.
Hundreds of workers attended a rally at the plant yesterday as the dispute over the future of the troubled site continues.
The company has written to the workers asking them to agree to changes to pensions and other terms as part of a survival plan, but the union Unite has accused the firm of giving workers an ultimatum of accepting worse pay and conditions or losing their job.
The plant was shut down last week as a result of the industrial dispute.
Calum MacLean, chairman of Ineos Grangemouth, said the company had received around 300 positive responses from the workforce yesterday.
Speaking at the site, he told BBC Radio Scotland: "We have several hundred acceptances already in. Today is of course the day that we expect most of those returns to be coming back after families have talked about the situation over the weekend.
"So we remain pretty confident that there's a strong support for the company."
Ineos has warned that the plant will close in 2017 without fresh investment and changes to workers' terms and conditions.
Mr MacLean told the Good Morning Scotland programme the site has made significant losses in recent years.
"People need to realise that as a site, this site's lost £150 million per year for the last four years," he said.
"It's got a pension fund which is £200 million in deficit and it is on the point of going bust, and if it wasn't because of the support of the shareholders today, who are funding those losses, then there's a very serious situation here which means the site may not start up again."
On Saturday, Scotland's First Minister Alex Salmond repeated a plea for unions to agree to no industrial action and for management to reopen the site in order for negotiations to take place.
Mr MacLean said today: "Alex Salmond's been quite clear that he says we should start up the plant, and we totally agree.
"We have had meetings with Alex and we said that we will start up the plant as soon as the unions say that they will not strike. It would be unsafe for us to start the plant up in the knowledge that the unions could take it again down at very short notice."
Around 400 employees, some with children and family, attended a rally at the plant yesterday in heavy rain and heard from speakers from Unite and other bodies such as the Scottish Trades Union Congress.
Unite's Pat Rafferty said the union has "continuously given assurances" that there will be no strikes from now until December.
He told BBC Radio Scotland: "In fact yesterday, at the rally here, I gave a committment that we would have no strikes for however long it took to allow negotiations to take place between ourselves and Ineos on the survival plan."
He insisted the union was not imposing any conditions on the no-strike pledge, as he attacked Ineos's approach to negotiations.
"Ineos wants to come to the negotiating table at the same time as threatening members and threatening people here with the sack in 45 days. You can't negotiate and impose at the same time," he told Good Morning Scotland.
"We'll place no conditions, we'll get there to the table, we'll negotiate. We will put absolutely no restrictions on what you want to speak about on that survival plan, including the pensions, including the shift allowances. We'll put no pre-conditions on that."
The company sent out a letter on Thursday to all 1,350 workers at the site asking them to indicate their support or rejection of the company's plan by 6pm today.
Mr Rafferty told the programme he expected the majority of people to reject the proposed new business plan once the deadline is reached.
Asked what message the Prime Minister would send to the two sides in the dispute, David Cameron's official spokesman said: "The message is that we would urge them to continue to talk and find a way to secure a long-term future for Grangemouth.
"The Government has been working with all sides in this. The responsibility is on them to try to find a way forward that secures the kind of future I have described.
"I think there is a responsibility on all sides here and that's why it is important that the continue to try to find an agreement that ensures a sustainable future for the facility."