The device known as shoyu-tai (or soy-sauce snapper in Japanese) was invented in 1954 by Teruo Watanabe, the founder of Osaka-based company Asahi Sogyo, according to a report from Japan’s Radio Kansai.
It was then common for glass and ceramic containers to be used but the advent of cheap industrial plastics allowed the creation of a small polyethylene container in the shape of a fish, officially named the “Lunch Charm”.
The invention quickly spread around Japan and eventually worldwide, and it is estimated that billions have been produced.
A Spanish company (I imagine there are a few worldwide) develops compostable bioplastic containers using PLA, polylactic acid, the most used plastic in 3D printing, in food safe formulations. I suppose there are limitations on what it can contain, and I don’t know if soy sauce is compatible. I know that it’s used for single serving olive oil, for example. There are challenges, like storage life, but it’s a good start.
I do a lot of 3D printing. Printing PLA things for food storage is not recommended, not because of PLA, but because filaments often have modifiers to enhance certain properties that may not be food safe, and because contact with materials and parts, like extrusion nozzles may add impurities that are probably not food safe…
The thing is that mass-produced plastic items (like the plastic fish in question) are typically not produced with 3D-printing, because that would be incredibly slow and inefficient.
Instead, basically some kind of oil or molten mass is pressed into a form and then cooled down/condensed into a solid object. This way you can rapidly produce thousands of plastic items per minute. There is no nozzle involved, and you can do with fewer additives because the mechanical press removes the need for the filament to be so fickly 3D-printable. It can basically do with a bit more crude types of plastics, so you need a bit less additives to make the plastics more mendable.
I never said that these should be produced via 3D printing, it would be both economically unfeasible, and very difficult to achieve food safety, as I have mentioned.
The process you are describing is injection molding, generally used for solid parts. In this case, a variation called blown injection molding, is used. In this case the material is injected into a mold, and then a gas is blown into the interior, to make the material stick to the inner mold, and create a cavity. Nozzles are involved, as they are used to inject the material into the mold. These nozzles can be made specifically to be food safe, with stainless steel, for example.
Keep in mind that PLA also leaks microplastics into food and could also be considered a risk to health just like other plastics.
Aren’t these biodegradable, though? I imagine the body would eventually process them, unlike hydrocarbon based plastics.
“Biodegradable” doesn’t mean “biodegradable in the conditions in the human body.” Lots of ‘green’ plastics are only compostable at a fairly high temperature (120F/50C) and with specific bacteria present.
PLA is not one of those. It’s used in biodegradable implants. Even fairly large bone screws will dissolve within a couple years.
Biodegradable ( “green” ) needs a new definition
I’ve started to see home compostable on some packages.
PLA isn’t food safe in 3d printing mostly because of layers on a print trap foreign material / bacteria and water can also seep into microscopic gaps into infill and it becomes a breeding ground. I doubt it would be useful for anything squeezy but it might be useful for single use forks and other utensils. But paper / wood can do those things already so I don’t see PLA being much use. For sachets I expect the answer is paper with some kind of biodegradable lining which gives a product a shelf life of a few years but does degrade in time.
Also, some “biodegradable” products are only compostable in specialist facilities where it can be shredded and broken down with water / heat / pressure. I think PLA is a bit like that. If you print something out of PLA and stick it out in the garden or even toss it into a compost bin it’ll still be there in 10 years although it might be faded, warped & brittle. Maybe it eventually biodegrades but it’s not quick enough.
The caveats you express are somewhat valid, but not totally correct. Printing correctly, with a food safe nozzle, path, and PLA formulation, is entirely possible. Simply printing in single layers, with a properly dialed in printer can eliminate your concerns. Medical items and implants are printed out of PLA, albeit with extreme production controls.
However, printing these single use items would be absolutely un-economical. 3D printing shines in short runs, bespoke items, like replacement part that are out of production, or which are very difficult to manufacture by other methods like injection or machining.
Its true that PLA, in unmodified form, has a much higher modulus than PP or PE, so squishiness is out of the question. What I have mentioned before is that I have bought single serve olive oil in PLA containers. From what I could see, these were injection molded and had a film top made from a plastic I never bothered to identify.
These containers were surprisingly elastic when crushed, not as elastic as other plastics, like PET, PP or PE, but much more than I had come to expect from my experience with the material. I’m going to attribute this to molding vs. extruding.
The hard part about PLA is that while it is biodegradable, it’s only in certain conditions/facilities who are set up for it, and it’s not very common around the country. I’m all for what the company is doing, and I already do see a lot of PLA products in fast food (like soda cups), but it doesn’t mean much if we don’t have the facilities to properly dispose of it.
Source: I do a modest amount of 3D printing
I’m definitely not a polymer expert, I also have my information from what I read as a hobbyist. My take is that while PLA will compost in commercial facilities, it will eventually biodegrade in a reasonable time frame, with minor impact to nature. Better than the alternatives, I guess.
How does it biodegrade though?
Just like disintegrate into tiny plastic molecules that we can no longer see but it’s still plastic? Or does it degrade as far as becoming the individual components that made up the plastic and can be recycled and used by things in nature?
If it breaks down into tiny pieces its not biodegradable. The definition of biodegradable is that its chemically “processed by nature”.
BTW, biodegradable does not necessarily mean innocuous. A lot of “natural” elements and compounds are toxic. Something may be biodegraded, and leave mercury as one of the resulting elements, for example.
Pla is poly lactic acid, so it breaks down into lactic acid and then further into water and CO2 with heat and bacteria exposure.
I don’t know. As I mentioned elsewhere I’m not a chemical engineer, but I imagine that being made from starches, it may be decomposed into digestible compounds. Just guessing here.
PLA is pretty brittle AFAIK. these need to be squeezed, so i’m not sure it’d do… perhaps they could add something to it? but whether that additive would also be compostable… it’d certainly make it non-recyclable
I used to buy the olive oil containers for a restaurant I owned. They worked quite well. Small single serving cups with a peel off lid. I don’t know if the lids were bioplastic, though.
Unfortunately while PLA is technically biodegradable, it requires very specific conditions that can only be achieved in dedicated facilities. So it’s not like you can throw it in the composting bin and be done with it. It will also survive for a long time in nature.
Sure, but PLA will eventually biodegrade, unlike things like polypropilene or polyethylene, which are incredibly useful precisely because of their imperviousness.
EDIT: I’m willing to bet that PLA IS biodegradable in home settings if the correct method is used, like the Berkeley method, which produces much higher heat than “heap” methods. The Berkley method can produce compost in under a month, via endothermic processes that generate relatively high heat. All you need at home are the compostable materials, and a roughly 1m cube, which can be made out of pallets, for example.