Techni-colour coats of polyurethane innovation

According to BMS, a PU coating of some kind appears in every car rolling off modern production lines. If not on the metal bodywork outside, then coating a plastic-based component inside, and with so much in today’s world requiring a covering or finish, the PU coatings business is huge.

According to the British Coatings Association, it takes two tonnes of paint to cover a Boeing 747 jumbo jet. A road vehicle might require a layered coating of less than 100µm - or the breadth of a human hair according to BASF – but with 85m vehicles expected to roll off production lines in 2015, the coatings business remains a big draw for manufacturers and developers.

At a Bayer MaterialScience (BMS) press conference in Dusseldorf, Germany in January 2015, Daniel Meyer, head of the coatings, adhesives, specialties business unit and member of the executive committee of BMS, told journalists it takes 1kg of isocyanate to coat one car.

“As of today, the overall share of polyurethane chemistry in OEMs is roughly about 30%,” he said.

“We needed 70 years to get from 0 to 30% - which tells you how conservative this industry is,” he said.

“Will we need another 70 years to get to 60%?” he asked.

PU already plays a large part in the flexible foam side of car production but, according to a 2014 report from MarketsandMarkets, the global automotive and transportation coatings market was almost 50% PU-based in 2012.

Michael Hilt, senior manager coating systems and painting technology and general manager business unit process industries at the Fraunhofer IPA Institute (Institute for Manufacturing Engineering and Automation IPA), said it is true that polyurethanes are challenging to create. But he added: “In use phase, they are sustainable and very high quality materials too.”

However, it is partly due to polyurethane’s “high quality” – to reiterate Hilt - that Meyer remains “confident that the acceptance rate for PU within the auto industry is now on an exponential growth path and that it is waterborne PU that all OEMs investing into,” he explained.

However, Meyer stressed new products have to make economic sense because consumers are not prepared to spend more on something just because it is made from bio-based or more sustainable materials or processes.

BASF’s auto coatings processes

In 2014, BASF’s coatings division announced had sales of coatings to third parties of EUR2.9bn. Volumes grew in Asia, North America and Europe, the company said. In BASF’s annual financial report, the automotive coatings division was singled out for praise for raising prices. The company said its OEM coating business developed successfully over 2014 thanks to growing demand in Asia, North America and Europe.

Not only automotive coating, the firm said, but also coil coating and windfarm rotor blade coatings, were in much greater demand during 2014. The Asia Pacific and South America, Africa and Middle East regions generated 22% of the overall demand for coatings, North America, 16% while at 40% it was Europe that generated the largest demand.

Spurred by the growth potential in Asian auto markets, a BASF auto coating plant in Bangpoo in Thailand is about to go live. Meanwhile, at Samuthprakarn (Bangpoo), the firm operates a system house for general polyurethanes with an annual capacity of 14kT to support customer growth in Thailand.

BASF is also targeting China - which analysts say is one of the fastest growing auto markets - for capacity and plant expansion.

BASF is spearheading this at Shanghai Coatings- - a joint venture between BASF and Shanghai Huayi. Together they will produce auto coatings at a new plant in the country’s most heavily-populated city.

Paint job

Car producers agree that the coating process of car manufacture is the most labour intensive of all the production stages.

Traditionally, there have been four paint layers: the EDC layer, which is also knowns as the electro-coating or e-coating phase of the process. Generally, this layer utilises PU-modified epoxy technologies. BMS supplies polyether and polyisocyanates for EDC coatings.

The primer/surfacer provides stonechip resistance and evens out the surface of the metal bodywork. Here, PU is

the material of choice due to its cross-linking and flexibility.

The basecoat layer provides the vehicle’s colour. The popularity of water-borne materials has brought PU to this phase of the paint job in recent years. Good adhesion to the primer surfacer, flexibility and rheological properties made PU a choice material for this coating layer.

The last layer is the clear coat. Back in 2012, BMS calculated that the share of this market using PU was 30%.

Auto coating innovation from BMS

Automotive OEM coatings are the most demanding of all since they have to withstand intense sun, ice, salt and other environmental challenges. According to BMS, polyurethane coatings “meet these challenges in an ideal way.”

Traditionally, auto coating relied on solvent-based PU coating systems, but largely due to environmental concerns, new low solvent, water-based coating systems are gaining in popularity.

In January 2015, BMS unveiled the world’s first PDI derivative as hardener for coatings and adhesives.

At the January press conference in Dusseldorf, Germany BMS outlined the benefits of a new thermolatent hardener.

According to Meyer, the product offers automakers a “significant time and cost advantage as well as substantial ecological savings potential.” He said the coating process is “currently the most expensive part of car manufacture.”

A study conducted by the project team showed the technology can reduce energy consumption by 15% and CO_₂ emissions by 10% compared with the best current process.

After application, the coating formulated with the thermolatent hardener initially flows unimpeded over the surface of the plastic, forming a uniform film, according to a BMS press release.

However, when the temperature is raised to about 90°C is the hardener activated and it ensures rapid curing of the coating on the plastic substrate. No significant changes to existing coating formulations are required, said Meyer. He also said that it was a significant development for auto coating processes.

“This development enables energy and cost-efficient mixed-material automotive coating for first time,” said Meyer.

Topcoats formulated with the new hardener cure up to 30% faster than with established two-component polyurethane coatings. In the medium term, topcoats will most likely be suitable for the mixed coating of plastic, composite and metal substrates, said Meyer.

BMS collaborated with the German research organisation Fraunhofer Institute and DURR – a machinery and plant manufacturer based in Bietigheim-Bissingen, Germany to develop the material.

Meyer said: “Our objective is to incorporate our partners along the value chain and their know-how into our development efforts as early as possible to ensure that our customers are successful in the market.”

Of course BMS is hopeful and ambitious but Hilt remains circumspect in the face of PU’s recognisable advantage to industry and said it could take the industry some time to pick up on new material developed by the collaboration.

“It could take the auto industry three years to take this technology up,” said Hilt.

FAW partnerships for growing Asian markets

The Asia Pacific markets offer the greatest prospect for growth for coating, especially in automotive. The Chinese state-owned automotive manufacturing firm, the FAW Group’s latest sales figures back this up. In February 2015, FAW revealed that its January sales reached 25,500 units, a jump of 16% on January 2014.

But, equal to the growth of the area’s markets is the growing power of its innovations and production processes.

A joint venture between the FAW Group and Germany's Volkswagen AG, Audi AG and Volkswagen Automobile Investment Co. will allow western manufacturers to harness some of the growth.

A $2.5bn production base that FAW-Volkswagen is setting up in Tianjin, North China, will be the biggest joint venture investment in the port city's manufacturing sector. It is expected to be operational in 2018.

In addition, Volkswagen is set to build two new auto plants in Tianjin and Qingdao, East China's Shandong Province, with the view to expanding production capacity.

However, the FAW Group, which is headquartered in Changchun, Jilin, is keen to establish partnerships with home-grown innovators.

Automotive manufacturer FAW Group signed contract in January 2014 with two Chinese coating makers, Tianjin Colouroad Coatings and Chemicals and Feiyang Novel Materials, to jointly develop energy-saving auto coatings including polyurea products.

The state-owned FAW Group claims to be the market leader in China’s vehicle manufacturing sector, with 120,000 employees and a sales volume of over 2m units/year.

Tianjin Colouroad has recently developed a new polyurea coating that it claims can raise the percentage of solids content in coatings from 55% to 75% and reduce the roasting temperature from 140℃ to 80℃.

Smart surface technology and self-healing paint

The arena for smart surfaces is wide open but Meyer told the press conference that “we will have to wait to see where smart coating takes us.” At the moment he does not consider it a sensible route for a great deal of R&D. He asked: “Is it the dream of technologists or something that people will pay for?”

In 2014, students from The University of Southern Mississippi’s School of Polymers and High Performance Materials developed a self-healing coating from chitosan - derived from chitin - the main component of the exoskeleton of crustaceans.

The network consists of an oxetane-substituted chitosan precursor incorporated into a two-component polyurethane. When the network is mechanically damaged, oxetane rings open to create reactive ends but when exposed to UV light, chitosan chain scission occurs, which forms crosslinks with the reactive oxetane ends, which repairs the network.

Also in 2014 Johnson Controls Inc and Yanfeng Automotive Trim Systems Co together announced plans to develop colour-changing panels for auto interiors.

According to Han Hendriks, vp advanced product development at JCI, it is the partnership’s “vision that every dumb plastic surface will become smart in some form or shape.”

“What you really want is when you enter a car is that it turns into your environment. So that you are able to create the specifics of the interior that you want to have, even if it’s not your car, but you enter it and the colours of the interior start to adapt to what you’ve programmed,” he said.

Future interior panels may have heating or cooling functions or be self-cleaning surfaces. The company’s research team is also experimenting with car interior surfaces that could change colours to match the motorist’s whim.

The work is being undertaken across three technical centres located in Dusseldorf, Shanghai and Holland, Michigan. Polyurethane has a part to play in it all.