Lets imagine that I have invented a new kind of bug repellent that targets one specific bug. This repellent uses a group of active ingredients to repel said bug. Each active ingredient does so in its own unique way.
Lets suppose i could not find any prior art concerning any of these ingredients and filed for a patent. The patent is granted and I start looking for license deals. But then suddenly another party determines that there is prior art for one of these ingredients and wants to start using this ingredient as a base for making a competing and cheaper repellent. The evidence for this prior art is rock solid. I had simply overlooked it.
Would this cause the entire patent to become invalid? Would it give others the right to make my repellent without permission even though there exists no prior art for any of the other active ingredients in my repellent?