You can freely build on Sticky, Tiny Plastic Balls Made from Acrylates

What this patent covers

This patent details the creation of microscopic, solid balls, called microspheres, that are inherently sticky and can be dispersed in solvents but don't dissolve in them. They are made from a blend of acrylate esters (like iso-octyl acrylate) and a small amount of another chemical, either an ionic monomer or maleic anhydride. The process involves suspending these ingredients in water and using a specific amount of emulsifier, a substance that helps mix oil and water, to create the microspheres. The resulting tiny balls are described as infusible, meaning they can't be melted down, and elastomeric, meaning they can stretch and return to their original shape.

What is now free to use

All 1 claims of US 3691140 are in the public domain. Specifically:

The 1 dependent claim add narrowing limitations and are also free.

What is NOT covered

Patent expiry frees this specific invention. Separately-patented improvements made after expiry may still be protected.

• Microspheres made from monomers other than alkyl acrylates and specific ionic monomers or maleic anhydride.

• Microspheres that are soluble in organic solvents.

• Microspheres created using polymerization processes that don't involve an aqueous suspension.

• Microspheres made with emulsifier amounts below the critical micelle concentration.

• Microspheres that are not inherently tacky or elastomeric.

Who is building on this today

3M, the original assignee's spin-off, continues to be a major player in adhesive technologies. Many companies involved in specialty polymers and adhesives likely build upon the foundational principles of microsphere synthesis and adhesive formulation described in this patent.

Products built on expired version of this technology

How to cite this patent in your documentation

Individual. US Patent 3691140. Acrylate copolymer microspheres. Granted 1972, expired 1990. Now in the public domain.

Note: This is a convenience citation. Consult a patent attorney for formal freedom-to-operate analysis.

PatentBrief is an educational resource and does not provide legal advice. Patent expiration information is derived from USPTO records and may not reflect continuation patents, divisional filings, or separately-patented improvements. For commercial use or production decisions, obtain a formal freedom-to-operate (FTO) opinion from a registered patent attorney.