On 16 Sep, 21:06, Chris ] wrote:
I am still using the ones I bought forty years ago!
I simply need a few more.

My Grandfather had a 'notepad' made of a plastic called Ivorine - mock
ivory - that he had for 60 years. The company used to make plant
labels and collar stiffeners. It shut down in 1995.

It seems to have been casein protein polymerised with formaldehyde,
and seems to have been more or less indestructible. The name is
currently used for cellulose acetate used for repairing of piano keys
and for veneer inlays. That's a different material.