Chewing gum bases typically consist of linear, amorphous polymers, which can easily become trapped in crevices on pavements and cost a great a deal of public money to remove.
Block copolymers
Wrigley’s latest invention uses a gum base made of block polymers, which are also known as block copolymers.
“They provide desirable elasticity during chewing. Moreover, if a chewed cud is improperly discarded and adheres to a rough environmental surface - most commonly a concrete sidewalk - the micro-domains prevent or reduce flow into the pores and cervices of the concrete making the cud easier to remove,” said Wrigley in its patent application.
20 seconds to clean
The company claimed that gum made through its method could be removed with typical high pressure water washing in 20 seconds leaving no more than 20% of residues.
It said it would even be possible to achieve the same result by pulling on the gum with fingers.
According to Wrigley, removability could be enhanced by adding additives such as emulsifiers and amphiphilic polymers such as Gantrez.
It said the gum base was suitable for sugared gums and formulations using sorbitol, mannitol or other polyols.
Gum litter
In the UK, local councils spend around £150m ($250m) annually on gum removal. The chewing gum industry has been pressed to find ways to reduce gum litter and some countries have even proposed gum taxes to go towards clean-up costs.
This had led two leading manufacturers, Wrigley and Mondelēz International, to earmark enviro-friendly gum as an R&D priority.
Wrigley told the UK Parliament in 2003 that it had invested around £5m ($8m) on research in the area but had no products ready for consumer testing.
Degradable gums
Wrigley’s competitors have been looking develop chewing gum that biodegrades faster than the five years it takes for conventional gum.
Number two gum player Mondelēz last year filed a patent for a degradable gum composition based on alternating co-polymers: C2-C10 alkene and maleic anhydride.
The company’s R&D subsidiary Reading Scientific Services Limited (RSSL) is also currently applying for EU novel foods for synthetic chewing gum base with methyl vinyl ether and maleic anhydride; also alternating co-polymers.
In 2012, UK firm Revolymer was granted EU novel foods approval for its Rev7 gum base that degrades between two to three months on pavements.
Gumlink and Fertin Pharma, divisions of the Danish Bagger-Sorensen Group, last year launched legal proceedings against Revolymer for allegedly infringing their patent on degradable gum by launching a nicotine gum with the Rev7 base in Canada.
In 2011, researchers from University College Cork, Ireland, patented a process for a non-sticky, biodegradable gum that uses cereal proteins, while a Dutch consortium, including TNO, are researching ways to make a similar gum. (See HERE and HERE)