Report by Liz White, editor
Albemarle developed its new aliphatic curing agent Ethacure 90 in response to requests from users for UV-stable one-coat materials, said Dr Sam Lane, business marketing manager.
Over three or four years, "we had a lot of customers asking for aliphatic cures," Lane said. Albemarle is the biggest supplier of aromatic curatives, with Ethacure 100, 200 etc - well known curatives that work well and are used globally, Lane said, giving polyurea coatings for China's high speed rail network as an example.
Although they work well, they are aromatics, and so not very stable to UV light. In time the colour changes, Lane explained.
"What some people will do is, they put the normal polyurea/polyurethane layer on and then come back and put an aliphatic coat on to give the required UV resistance," the Albemarle expert said, speaking 11 Oct, in an interview during the 2010 conference of the Center for the Polyurethanes Industry, held in conjunction with the UTECH North America 2010 exhibition in Houston, Texas.
"That's the get-around to give a colour-stable layer," Lane continued.
This top layer is often a thin - 3-5 mil (0.09 mm) - layer on top of the base coat which can be perhaps 80 mil thick, he added. "If you get any kind of abrasion or wear the aliphatic layer can be scraped away and then the colour stability problem arises again," Lane said, noting that "this is a long-standing problem with any kind of spray polyurea." ·
In addition, some of the existing aliphatic technologies have low elongation, which can be problematic when trying to coat surfaces with sharp contours where "bendability" is crucial.
But, if the cure was aliphatic, UV stability would be good and no top layer would be needed, the Albemarle manager commented.
The fast reactivity of aliphatics can be an issue. "When they get too fast they won't spray very well, this can cause spray guns to clog quickly," he said, noting that viscosity builds up very rapidly.
"There has never been a slow enough aliphatic to use in formulating to allow for good spraying and processing," he said.
Albemarle used "a big screening programme to look at aliphatics: Ethacure 90 came out of this," Lane said.
He stressed that it is now, "quite rare for a new curative to come on the market - because of the costs involved in screening, testing, evaluation." The time and costs involved for extensive testing are some reasons "Why you don't see many new curatives," Lane said.
Albemarle's new curative has cleared US regulatory hurdles, Lane said. Commercial sales started in December. Meanwhile, toxicity/ environmental testing is under way for the rest of the global registrations, and that will be finished in late 2011/early 2012, Lane said.
Colour-stable polyurea coatings
Users now have the ability to have a one-coat polyurea coating, in any colour, Lane said. "White will stay white, blue, blue," he said. As an example, Lane said, "Pretty much all truck beds are black in North America," since "a lot of pigment is added, to hide the fact that the coating is actually changing colour," he said.
With Ethacure 90, however, OEMs can now have a dark-blue lining on a light- blue truck, or match the liner to the body coat colour, the marketing potential is large, Lane added.
Coatings for concrete/steel in potable water systems are another prospective use, since aliphatic amines have a good HSE (health, safety, environmental) profile versus aromatic types, he added.
Aliphatic systems are also being used in retrofitting old water systems, as is done in the UK, where a considerable amount of remedial
work on the water systems is being carried out.
Ethacure 90 was designed to be slow curing - "slower than you actually need, because that gives you some flexibility in the formulating," Lane said. Users can add faster -curing IPDA (isophorone diamine) and other primary amines, to lower cost and adjust speed, he said.
Albemarle opted for one of the slowest curing aliphatic amines from the screening. That gives users "the ultimate flexibility," Lane added. They can always adjust the formulation to speed the process up, he said.
Lane noted that polyurea use in Europe is at a lower level than in the US, but said that European use is growing, and Asian use has "really picked up," with big projects in spraying steel and concrete in major building projects such as the Beijing Olympics. Potential users are where visual impact is important, he said.
Aliphatic materials currently form about 5 percent of the polyurea market, "but we feel that may change with these new materials" Lane said.
Lane feels this new material will reach a larger proportion of the polyurea business.
Users need a reason to change, because aliphatics are more expensive, Lane said. But he thinks with time the cost of the aliphatic amine curatives will come down. And, he added, "you get what you pay for - in this case formulation flexibility and cure rate control."
Albemarle has "really started to want to be a solution provider in curatives, driven largely by customer wishes, for a wider range from Albemarle," Lane concluded.